This section is both for:

  • Antigravity: things that fight the force of gravity; such as matter that "falls upwards", gravitational repulsion and gravity shielding

  • Paragravity: gravity generators, where you put electricity into one end and synthetic gravity comes out the other

Yes, the two categories tend to blur into each other sometimes. And both kind of blur into the cataegory of reactionless drives.

Gravity is such a pesky thing. It prevents us from doing all sorts of wonderful things. Such as floating through the air like a balloon, traveling into orbit without paying an ugly cost in delta V, and being morbidly obese but still light on your feet like Baron Vladimir Harkonnen

By the same token, it would also be incredibly useful to be able to create gravity on command. Then you could do things like create artificial gravity inside your spacecraft without unwieldy centrifuges, preventing the crew from getting killed by multi-gee acceleration, and make attractor beams.

And do idiotic things like make the direction of "up" in your spacecraft at ninety degrees to the direction of thrust like they were space-going passenger airplanes (I'm looking at YOU Star Trek, Star Wars, Battlestar Galactica, and practically every other media SF show and movie).

Science has yet to figure out how to make either device, but they have been popular in science fiction at least since H. G. Wells wrote The First Men in the Moon in 1901.

Another popular trope is mounting an antigravity/paragravity drive inside a submarine to make Instant Spaceship.

Of course the easiest way to create an antigravity device is to attach a piece of buttered toast (butter side up) to the back of a cat and drop it.

And as a note on terminology, things in this section will be using "Gravitational Waves." The term "Gravity Waves" has already been appropriated by the science of fluid dynamics, they refer to ocean waves.


"Anti" means "opposed to, against". So antigravity is something that fights gravity. These include:

  • Bizzare elements or minerals that fall upward, instead of downward as is customary. These include:
  • Gravity fields of opposite sign to conventional gravity, so it repels instead of attracts. These include:
  • Gravity shielding that screen off the effect of gravity. Scientifically accurate shields will require tremendous amounts of energy. These include:
  • None of the above:
    • Gravity Drag from Larry Niven's Known Space series. The device converts a spacecraft's momentum relative to the nearest large mass into heat, which is jettisoned by a radiator. It acts like a high-tech parachute.

As a side note, understand that the astronauts in the International Space Station are NOT floating around in microgravity because they are beyond the range of Terra's gravitational field. The gravitational attraction of Terra at the altitude of the ISS is about 93% of one full gee, almost full strength.

The reason that everybody floats around is because they are in a state of "free fall." If you were in an elevator, and the cable snapped, you too would be in a state of free fall and would float around. At least until you hit. The station and astronauts are in free fall because they are in "orbit", which is a clever way to fall but never hit the ground. You can read more about the details here.

So people in the Space Station are in "zero gravity" in the sense of "undergoing an acceleration of 0.0 gs". Just like the Apollo astronauts are crushed by an acceleration of 3.94 g when they lift off. They are NOT in "zero gravity" in the sense of they are out of range of Terra's gravity.

Related terms are "free fall" and "microgravity."


(ed note: Rob Garitta asked a question about the minimum energy requirements for some kind of paragravity hover vehicle, like Luke Skywalker's landspeeder or a Traveller air/raft. Not the energy to move around, just the energy to hover in place.)


     If you suspend something above the ground and it is not moving, it requires no energy at all to keep it there. The speed of the object is not changing, it is not gaining kinetic or potential energy, so no energy is needed to keep it in place.
     For example, I am currently using a device that exerts a repulsive force on the ground to suspend me about half a meter above the ground. It is called a chair. It requires no power to operate.
     Obviously, you can suspend things using less efficient methods, like quadrotor drones, which must spend power to continually shoot streams of air downward (accelerating the air, and giving it kinetic energy, which comes from the drone's battery).
     Now if you move the object around, it will require energy to speed it up so that it can get someplace else (and to fight aerodynamic drag), or to raise the object against gravity. Conversely, in principle lowering the object or slowing it down can get you that energy back (minus inefficiencies, and you're not going to recover any energy lost to drag forces or friction).
     I assume you're talking about some kind of magic repulsor beam or force-screen levitator car or some such. In principle, there's no reason that these need to consume power to keep something hovering in one spot — especially if it acts by directly pushing from the levitated object down to the ground. Of course, we don't actually have any real-life examples of levitator rays to compare to. There may be additional energy losses associated with such a technology — ionization of the air*, or excitation of energetic modes not related to creating bulk forces, or modulation of the field to overcome dynamic instabilities through active control, or radiation of orgone waves, or who knows what. But none of this follows from the fundamental physics of the situation.
     * Note that if the device ionizes the air, it will produce ozone which is a major cause of air pollution. If repulsor rays ionize the air your cities either very tightly regulate levitator cars or they are full of smog and everyone has breathing difficulty.


     Luke Campbell Do you have any idea how to calculate the power needed to lift a mass with my magic levitator ray?


     Rob Garitta The power to lift a mass (absent inefficiency) is easy — multiply the mass of the object by the distance lifted, and then multiply that by the local gravity.

(ed note: meaning the following equations are for a device with 100% efficiency. Since there is no such thing as 100% efficiency, you should make a correction. If you say the device is only 75% efficient, the efficiency factor is 0.75. The power factor is 1 / 0.75 or 1.33. Multiply the equation's power required by 1.33 to get how much power it really uses.)

     For example, on Earth the gravity is 10 m/s2 (actually 9.8 m/s2, but rounding to 10 is easier for quick calculations). If your hovercar has a mass of 1500 kg, and is currently floating at an altitude of 40 meters, and you want to lift it to a height of 60 meters, then the energy required to do so is:

Powerreq = gp * Massobj * (Altfinal - Altinit)


Powerreq = energy required to lift the object (Joules), divide by 3,600,000 to convert to kilowatt-hours
gp = local planetary surface gravity (m/s2) = 9.81 m/s2 for Terra's surface
Massobj = mass of the object being lifted (kg)
Altinit = initial altitude from planet's surface (m)
Altfinal = final altitude from planet's surfac (m)


(10 m/s2) * (1500 kg) * (60 m - 40 m)
= 300,000 kg m2/s2
= 300,000 Joules = 0.08 kilowatt-hours
( = 300,000 * 1.33 = 399,000 J if device is only 75% efficient)
     Note that if you drop in altitude, that potential energy that you added is returned somehow.

(ed note: you take the final altitude and subtract the initial altitude. If the final altitude is less than the initial, the object is dropping in altitude not lifting in altitude. This means the altitude changes will be negative. Which means the energy required will also be negative, signifying that the hovercar's batteries will be gaining energy instead of losing energy.)

     You can just turn it into kinetic energy, which gives your hovercar speed — but if you brake with the levitator ray you will be doing work on the ray's field, which will be adding energy to the ray. You can use this to, for example, recharge the battery.

(ed note: once the battery fills up the hovercar will have to get rid of the added energy as waste heat or the battery will explode)

     Things get a bit trickier if you go high enough that the gravitational field is no longer uniform (meaning the gravity at the initial altitude is drastically different from the gravity at the final altitude, i.e., lifting from the planet's surface into orbit). In that case if you start at a height from the planet's center (NOT the surface) of r0 and you go to a height of r from the planet's center, then the energy required is

Powerreq = (G * M * m / r) - (G * M * m / r0)


Powerreq = energy required to lift the object (Joules), divide by 3,600,000 to convert to kilowatt-hours
G is the gravitational constant (6.67408×10-11 m3⋅kg-1⋅s-2)
M is the mass of the planet (5.97237×1024 kg for Terra)
m is the mass of the thing you are levitating
r0 is the initial distance from the planet's center (6,371 m for Terra's Surface)
r is the final distance from the planet's center
     G can be looked up on Wikipedia (6.67408×10-11), and M and r0 for ground level for any of the planets in our solar system can also be found on Wikipedia (the entry for Earth, for example, lists all the relevant planetary parameters in the sidebar).
     If you speed up from a speed of v0 to a speed of v, this also requires an energy of 0.5 * m * (v^2 - v0^2). Likewise, slowing down somehow turns that energy into another form, which may just be dissipated as heat (as with friction brakes, or drag-producing aerodynamic surfaces), but might be used to recharge the battery (like with electric cars, that run their motors in reverse to work as generators).

     There are certainly levitation methods that use a lot of power. An extreme example is lifting something by light pressure, which requires a power of 3 GW to lift 1 kg against Earth's surface gravity. (Although if you re-use the light, by reflecting it back and forth between two mirrors, for example, you can reduce the power level. If you get on average 1000 reflections per photon, then your power level is down to 3 MW per kg. You still have a nasty death ray ready to incinerate anything between the levitated thing and the emitter station, though). Sonic levitation (where you have to continually run a speaker) or rotorcraft (helicopters, quadrotor drones) also continually use power.
     On the other hand, magnetic levitation does not intrinsically use power to keep something suspended. Active control circuits will require some dissipation (probably because they use some electromagnets for control, which have resistive losses). For superconductive levitation, you will need power to run the compressors that get you your liquid nitrogen (unless you have room temperature superconductors in your setting, or if you are working in a naturally cryogenic environment like Pluto, in which case you don't need any power).
     And yes, if you lift yourself up above the atmosphere and then turn off your levitator ray, you will drop like a rock unless you also add enough speed to keep in orbit. Note that the energy to add orbital speed is quite a bit more than the energy to just lift you up above the atmosphere.

From Dr. Luke Campbell in a private Google Plus thread (2017)

Buck Rogers Inertron

Anthony Rogers made his first appeance in a 1928 story called Armageddon 2419 AD by Philip Francis Nowlan (synopsis here, public domain text here). It was followed by a sequel: The Airlords of Han (public domain text here). In 1929 it was turned into a newspaper comic strip: Buck Rogers in the 25th Century A.D.

The main item relevant to our interest is the antigravity material "inertron", which falls upward. Its main use is as "anti-ballast". By loading an aircraft with inertron anti-ballast, its weight (but not its inertia) is reduced. The effect is to drastically reduce the amount of thrust required to just keep the aircraft in the air. Later in the comic strip, this is used to make interplanetary spacecraft.

People use "jumping belts", a back pack full of enough inertron to reduce the user's weight to only a few kilograms. This allows the user to make jumps in excess of 15 meters (50 feet). Later, in the comic strip, small rocket engines are added to make flying belts.


[Inertron] is a synthetic element…It reflects 100 percent of the heat and light impinging upon it. It does not feel cold to the touch, of course, since it will not absorb the heat of the hand. It is a solid, very dense in molecular structure despite its lack of weight…It is a perfect shield…in many ways resembles the fabled hypothetical antimatter. It can co-exist with matter from our universe without mutual destruction, but it doesn’t much like to. Given a choice, it will try and head to the nearest perfect vacuum — which, from a terrestrial point of view, is always straight up. Thus it forms an effective anti-gravity agent. It also has the happy faculty of being a nearly 100% perfect insulator against any and all forms of electromagnetic radiation.

From ARMAGEDDON 2419 AD by Philip Francis Nowlan (1928)

Antigravity Lifters

Antigravity is currently handwavium, physics currently does not allow the possiblity of antigravity flatbed trolleys or hand truck. But they are too cool for school, most science fiction fans love them.

An antigrav trolley loaded with cargo will require energy (presumably electrical) to rise off the ground and move upward. If it lowers itself, the energy comes back and can be stored in a battery. Oddly enough, it requires zero energy to hover at a given height.

Understand that it still is going to take some effort to pull the blasted trolley. It doesn't matter that hovering will give it the equivalent of perfectly frictionless wheels, the cargo still has inertia. Your average automobile has close to frictionless wheels as well, but it still takes several people to push it anywhere. And by same token, once you have got it moving it will take about the same effort to stop the blasted thing.

Now if the antigrav trolley only rises a few kilometers off the ground you can calculate the energy required with the equation below. A more complicated equation will be needed if the trolley is going to rise into orbit or otherwise rise to a level where the value of gravitational acceleration is significantly different.

Powerreq = gp * Massobj * (Altfinal - Altinit) * (1 / eff)


Powerreq = energy required to lift the object (Joules), divide by 3,600,000 to convert to kilowatt-hours
gp = local planetary surface gravity (m/s2) = 9.81 m/s2 for Terra's surface
Massobj = mass of the object being lifted (kg)
Altinit = initial altitude from planet's surface (m)
Altfinal = final altitude from planet's surface (m)
eff = efficiency of converting electricity to antigravity (1.0 = 100%, 0.75 = 75% etc.)

Say you have a crate of 50 blaster rifles (mass 170 kilograms) plus a 50 kilogram crate of (black-market) antiagathic drugs. The trolley weighs 10 kilograms Total mass 230 kilograms. You are on Terra, standing on a superhighway clover-leaf 29 meters off the surface. You want the antigrav trolley to hover 1.5 meters off the road (30.5 m off the surface). Trolley has an efficency of 0.70 (70%). How much energy will the trolley need?

Powerreq = gp * Massobj * (Altfinal - Altinit) * (1 / eff)
Powerreq = 9.81 * 230 * (30.5 - 29) * (1 / 0.70)
Powerreq = 9.81 * 230 * (1.5) * (1.43)
Powerreq = 4,840 Joules or 0.00134 kilowatt-hours or 1.34 watt-hours

Thus at thirty—Avalonian reckoning—Christopher Holm was tall, slender, but wide-shouldered. In features as well as build, he took after his mother: long head, narrow face, thin nose and lips, blue eyes, mahogany hair (worn short in the style of those who do much gravbelt flying), and as yet not enough beard to be worth anything except regular applications of antigrowth enzyme. His complexion, naturally fair, was darkened by exposure. Laura, a G5 star, has only 72 percent the luminosity of Sol and less ultraviolet light in proportion; but Avalon, orbiting at a mean distance of 0.81 astronomical unit in a period of 0.724 Terran, gets 10 percent more total irradiation than man evolved under.

He made the customary part-by-part inspection of his unit before he put arms through straps and secured buckle at waist. The twin cone-pointed cylinders on his back had better have fully charged accumulators and fully operating circuits. If not, he was dead. One Ythrian couldn't hold back a human from toppling out of the sky. A couple of times, several together had effected a rescue; but those were herders, carrying lassos which they could cast around their comrade and pull on without getting in each other's way. You dared not count on such luck. O God, to have real wings!

He donned a leather helmet and lowered the goggles which were his poor substitute for a nictitating membrane. He sheathed knife and slugthrower at his hips. There would be nothing of danger—no chance of a duel being provoked, since a Khruath was peace-holy—not that deathpride quarrels ever happened often—but the Stormgate folk were mostly hunters and didn't leave their tools behind. He had no need to carry provisions. Those would be supplied from the family stores, to which he contributed his regular share, and ferried to the rendezvous on a gravsled.

Going out the door, he found himself on ground level. Humans had ample room on Avalon—about ten million of them; four million Ythrians—and even here in Gray, the planet's closest approximation to a real city, they built low and widespread. A couple of highrises sufficed for resident or visiting ornithoids.

Arinnian flicked controls. Negaforce thrust him gently, swiftly upward. Leveling off, he spent a minute savoring the view.

From THE PEOPLE OF THE WIND by Poul Anderson (1973)

(ed note: this is technically not antigravity, but has many of the same advantages and limitations. This was written in 1951, back when the Soviet Union still existed)

      The essential thing was that, while blowing on a spoonful of red cabbage soup. Professor Rojestvensky happened to think of an interesting inference or deduction to be drawn from the Bramwell-Weems equation expressing the distribution of energy among the nucleus-particles of the lighter atoms. The Bramwell-Weems Equation was known in Russia as the Gabrilovitch-Brekhov Formula because, obviously, Russians must have thought of it first. The symbols, however, were the same as in the capitalist world.

     Weeks passed, and nothing happened. That was a bad month in Russian science. The staffs of Medical Research and Surgical Advancement had already reported everything they could dream up. Workers in Aerodynamic Design weren’t sticking out their necks. The last man to design a new plane went to prison for eight years when a fuel line clogged on his plane’s test flight.

     Aerodynamic Design sent him out to Omsk to get Professor Rojestvensky to check his calculations. It was a shrewd move. The Nuclear Fission man and Professor Rojestvensky got along splendidly. They ate red-cabbage soup together and the professor O.K.’d the whole project. That made him responsible for anything that went wrong and Aerodynamic Design, en masse, was much relieved. They sent in a preliminary report on their intentions and started to make one gadget themselves. The Nuclear Fission man was strangely willing to play along and see what happened. He supervised the construction of the thing.

     It consisted of a set of straps very much like a parachute harness, hung from a little bar of brass with a plating of metallic sodium, under another plating of nickel, and the whole thing enclosed in a plastic tube. There was a small box with a couple of controls. That was all there was to it.

     When it was finished, the Nuclear-Fission man tried it out himself. He climbed into the harness in the Wind Tunnel Building of Aerodynamic Design’s plant, said the Russian equivalent of “Here goes nothing!” and flipped over one of the controls. In his shakiness, he pushed it too far. He left the ground, went straight up like a rocket, and cracked his head against the three-story-high ceiling and was knocked cold for two hours. They had to haul him down from the ceiling with an extension ladder, because the gadget he’d made tried insistently to push a hole through the roof to the wide blue yonder.

     When he recovered consciousness, practically all of Aerodynamic Design surrounded him, wearing startled expressions. And they stayed around while he found out what the new device would do. Put briefly, it would do practically anything but make fondant. It was a personal flying device, not an airplane, which would lift up to two hundred twenty-five pounds. It would hover perfectly. It would all by itself, travel in any direction at any speed a man could stand without a windshield.

     True, the Rojestvensky Effect which made it fly was limited. No matter how big you made the metal bar, it wouldn’t lift more than roughly a hundred kilos, nearly two-twenty-five pounds. But it worked by the fact that the layer of metallic sodium on the brass pushed violently away from all other sodium more than three meters away from it. Sodium within three meters wasn’t affected. And there was sodium everywhere. Sodium chloride—common table salt—is present everywhere on Earth and the waters under the Earth, but it isn’t present in the heavens above. So the thing would fly anywhere over land or sea, but it wouldn’t go but so high. The top limit for the gadget’s flight was about four thousand feet, with a hundred-and-fifty-pound man in the harness. A heavier man couldn’t get up so high. And it was infinitely safe. A man could fly night, day, or blind drunk and nothing could happen to him. He couldn’t run into a mountain because he’d bounce over it. The thing was marvelous!

     Aerodynamic Design made a second triumphant report to the Politburo. A new and appropriately revolutionary device—it was Russian—had been produced in obedience to orders. Russian science had come through! When better revolutionary discoveries were made, Russia would make them! And if the device was inherently limited to one-man use—ha-ha! It gave the Russian army flying infantry! It provided the perfect modern technique for revolutionary war! It offered the perfect defense for peaceful, democratic Russia against malevolent capitalistic imperialism! In short, it was hot stuff!

     As a matter of fact, it was. Two months later there was a May-Day celebration in Moscow at which the proof of Russia’s superlative science was unveiled to the world. Planes flew over Red Square in magnificent massed formations. Tanks and guns rumbled through the streets leading to Lenin’s tomb. But the infantry— where was the infantry ? Where were the serried ranks of armed men, shaking the earth with their steady tread? Behind the tanks and guns there was only emptiness.

     For a while only. Far, far away, the flying infantry appeared!

     Shoulder to shoulder, rank after rank, holding fast to lines like dog leashes that held them in formation, no less than twelve thousand Russian infantrymen floated into the Red Square some fifteen feet off the ground. They were a bit ragged as to elevation, and they tended to eddy a bit at street corners, but they swept out of the canyons which were streets at a magnificent twenty-five miles an hour, in such a display of air-borne strength as the world had ever seen before.

     The other was the bitter protest made by the Russian ambassador in Washington. He denounced the capitalist-economy-inspired prevention of the shipment to Russia of an order for brass rods plated with metallic sodium, then plated with nickel, and afterward enclosed in plastic tubes. State Department investigation showed that while an initial order of twelve thousand five hundred such rods had been shipped in April, there had been a number of fires in the factory since, and it had been closed down until fire-prevention methods could be devised. It was pointed out that metallic sodium is hot stuff. It catches fire when wetted or even out of pure cussedness it is fiercely inflammable.

     This was a fact that Aviation Production in Russia had already found out. The head man was in trouble with his own friends in the Politburo for failing to meet production quotas, and he’d ordered the tricky stuff—the rods had to be dipped in melted sodium in a helium atmosphere for quantity production—manufactured in the benighted and scientifically retarded United States.

     There was another item that should be mentioned, too. Within a week after the issue of personal fliers to Russian infantrymen, no less than sixty-four desertions by air to Western nations took place. On the morning after the first night maneuvers of the air-borne force, ninety-two Russians were discovered in the Allied half of Germany alone, trying to swap’ their gadgets for suits of civilian clothes.

     They were obliged, of course. Enterprising black marketeers joyfully purchased the personal fliers, shipped Them to France, to Holland, to Belgium, Sweden, Norway, and Switzerland, and sold them at enormous profits. In a week it was notorious that any Russian deserted from the flying infantry could sell his flight-equipment for enough money to buy forty-nine wrist watches and still stay drunk for six months. It was typical private enterprise. It was unprincipled and unjust. But it got worse.

     Private entrepreneurs stole the invention itself. At first the units were reproduced one by one in small shops for high prices. But the fire-hazard was great. Production-line methods were really necessary both for economy and industrial safety reasons. So after a while the Bofors Company, of Sweden, rather apologetically turned out a sport model, in quantity, selling for kronen worth twelve dollars and fifty cents in American money. Then the refurbished I. G. Farben put out a German type which sold openly for a sum in occupation marks equal to only nine eighty American. A Belgian model priced—in francs—at five fifty had a wide sale, but was not considered quite equal to the Dutch model at guilders exchanging for six twenty-five or the French model with leather-trimmed straps at seven dollars worth of devaluated francs.

     The United States capitalists started late. Two bicycle makers switched their factories to the production of personal fliers, yet by the middle of June American production was estimated at not over fifty thousand per month. But in July, one hundred eighty were produced and in August the production—expected to be about three hundred thousand—suddenly, went sky-high when both General Electric and Westinghouse entered the market. In September American production was over three million and it became evident that manufacturers would have to compete with each other on finish and luxury of design. The days when anything that would fly was salable at three fifty and up were over.

     The personal flier became a part of American life, as, of course, it became a part of life everywhere. In the United States the inherent four-thousand-foot ceiling of personal fliers kept regular air traffic from having trouble except near airports, and flier-equipped airport police soon developed techniques for traffic control. A blimp patrol had to be set up off the Atlantic Coast to head back enthusiasts for foreign travel and Gulf Stream fishing, but it worked very well. There were three million, then five million, and by November twelve million personal-flier- equipped Americans aloft. And the total continued to rise. Suburban railways — especially after weather-proof flying garments became really good — joyfully abandoned their short-haul passenger traffic and all the railroads settled down contentedly to their real and profitable business of long-haul heavy-freight carriage. Even the air lines prospered incredibly. The speed-limitation on personal fliers still left the jet-driven plane the only way to travel long distances quickly, and passengers desiring intermediate stops simply stepped out of a plane door when near their desired destination. Rural residential developments sprang up like mushrooms. A marked trend toward country life multiplied, Florida and California became so crowded that everybody got disgusted and went home, and the millennium appeared to be just around the corner.

     But borders were not only crossed by friends. Smuggling became a sport. Customs barriers for anything but heavy goods simply ceased to exist. The French national monopoly on tobacco and matches evaporated, and many Frenchmen smoked real tobacco for the first time in their lives. Some of them did not like it. And there were even political consequences of the personal-flier development. In Spain, philosophical anarchists and syndicalistos organized political demonstration. Sometimes hundreds of them flew all night long to rendezvous above the former royal palace in Madrid—now occupied by the Caudillo—and empty chamber-pots upon it at dawn. Totalitarianism in Spain collapsed.

     But in some ways the change has not been as great as one might have expected. About a year after the world was remade, an American engineer thought up a twist on Professor Rojestvensky’s figures. He interested the American continental government and they got ready to build a spaceship. The idea was that if a variation of that brass-sodium-nickel bar was curled around a hundred-foot-long tube, and metallic sodium vapor was introduced into one end of the tube, it would be pushed out of the other end with some speed. Calculation proved, indeed, that with all the acceleration possible, the metallic vapor would emerge with a velocity of ninety-eight point seven percent of the speed of light. Using Einstein’s formula for the relationship of mass to speed, that meant that the tube would propel a rocketship that could go to the Moon or Mars or anywhere else.

From HISTORICAL NOTE by Murray Leinster (1951)

(ed note:The protagonist is a young woman named Simsa living on a medieval level planet, in the ancient city of Kuxortal. The planet is irregularly visited by Terran starships who trade for some local items, but mostly use the place for money laundering and transshipping illegal cargoes hidden from the eyes of the the Patrol. There is a Prime-Directive technology-embargo against selling high-tech Terran equipment to the natives, since They Are Not Ready.

Thorn is a Terran off-worlder, who is seeking a remote archeological dig his brother was investigating, before the brother was murdered. Simsa and Thorn arrive at the edge of the desert of death in a little sail boat. Simsa is rather upset when she discovers that Thorn had cut up the sail in order to make some contraption. This means they are marooned, the boat is now worthless.)

      The mad off-worlder! While she had been lazing away the day he had done this!
     Not only had he stripped away most of the decking on the main portion of the boat, but he had taken the sail, slit it into strips. To make what? The thing which rested on the shingle was a monstrous mixture of hide-cloth from the sail, pieces of wood ripped and then retied into what looked like a small boat—except that it was flat of bottom. To it, while she had been unconscious, he had also transferred and lashed into place the rest of their food hampers, and now he was coming for the water jars.
     Did the alien propose to drag that thing of his? Or would he harness the both of them to it and work her as well until they both yielded to heat and exhaustion?
     If that was his plan, he would discover that she was not going to beg off—she would keep with him stride by stride as long as she could—or he would drive them both to the impossible. So when she came to stand beside him she looked for the drag ropes. There was only one—a single strand which she believed could not take the weight of the thing he had built.

     He asked no help of her, but faced the drag carrier front on. His hand touched his belt for a moment. Then, to her amazement, the impossible happened before her eyes. There was a trembling of the carrier. It arose from the gravel and hung in the air—actually in the air—at least the height of her own knee. Picking up the lead rope, Thorn set off along the narrow beach and the thing floated after him as if it were some huge wingless zorsal, as obedient to his will as her own birds were to hers.

     For a long moment, she simply watched what she still could not believe. Then she took off in a hurry, lest he vanish from sight. What new wonders he might bring into their service she could not guess, but now she would willingly accept all the strange tales which were told of the starmen and what they could do. Even though they never, as far as she knew, had demonstrated any such powers on this world before.
     Her anger lost in her need to know how such a thing might be, Simsa slipped and slid, forgetting her drained strength until she came even with Thorn who walked steadily ahead, leading his floating platform.
     “What do you do?” she got out between gasps of breath as she caught up. “What makes it hang so in the air?”

     She heard him actually give a chuckle and then the look he turned on her was alive with sly humor.
     “If you told those at the port what you now see, they would send me back to my home world, sentenced to stay out of space forever,” he told her, though he seemed only amused at being able to explain what must be a crime among his kind. “I have merely applied to this problem something common on other planets—ones more advanced than yours. And that is a deadly crime according to the laws by which we abide. There is a small mechanism I planted at the right spot back there—” he pointed with his thumb over his shoulder but did not turn his head, “which nullifies gravity to a small extent—

     “Nullifies gravity,” she repeated, trying to give the strange words the same sound as he had. “I do not know—some people believe in ghosts and demons, but Ferwar said they are mainly what those who believe in them make for themselves by their own fears—that you can believe in any bad dream or thing if you turn your full mind to it. But this is no ghost nor demon.”
     “No. It is this.” They were into the cut of the valley now. The sea wind behind them made the passage more bearable now than she could ever have believed it could be when she had seen it by day. Now as he halted for a moment, it was still not too dark for her to make out what he pointed to as he repeated, “It is this.”
     “This” was what appeared as a black box no bigger than could be covered by his hand were he to set that palm down over it. The thing rested directly in the middle of his drag carrier and now she could see that the cargo on board had been carefully stacked in such a way that the load must weigh evenly along the full length, leaving open only that one spot in the exact center vacant, the place in which sat the box.
     “You toss a stone into the air and it falls,” he said, “it is the attraction of the earth which pulls it down. But if that attraction could be broken sufficiently—then your stone would float. On my world, we wear belts with such attachments which give us individual flying power when they are mated with another force. We can move also much heavier things than this with little trouble. Unfortunately, I could not smuggle through the field guards as large a nullifier as I wanted. This is limited; you see how close to the ground the weight holds it.
     “There is this also—the power is limited. However, it is solar powered and here the sun can renew it, at least for the space in which I think we shall have need of it.”

     Simsa could understand his words easily enough, but the concept they presented was so far from anything she had known that his speech was akin to a wild travel tale, such as the river traders might use to scare off the gullible from their own private ports of trade, as was well known they were apt to do. She thought of such a thing being attached to a belt so that one could share the sky with such as the zorsal and the uses one could put such skill to.
     “The Thieves Guild,” she spoke aloud her own train of thought. “What they would not give for such as that! No,” a shiver which was not from the cooling of the wind shook her, “no, they would kill for that!

From FORERUNNER by Andre Norton (1980)

I went through the gateway, towing my equipment in a contragravity hamper over my head. As usual, I was wondering what it would take, short of a revolution, to get the city of Port Sandor as clean and tidy and well lighted as the spaceport area. I knew Dad's editorials and my sarcastic news stories wouldn't do it. We'd been trying long enough.

The elevator door opened, and Lautier and the professor joined in the push to get into it. I hung back, deciding to wait for the next one so that I could get in first and get back to the rear, where my hamper wouldn't be in people's way. After a while, it came back empty and I got on, and when the crowd pushed off on the top level, I put my hamper back on contragravity and towed it out into the outdoor air, which by this time had gotten almost as cool as a bake-oven.

     Ramón Llewellyn was saying to Joe Kivelson: "We're one man short; Devis, Abdullah's helper. Hospital."
     "Get hurt in the fight, last night? He was right with us till we got out to the elevators, and then I missed him."
     "No. He made it back to the ship about the same time we did, and he was all right then. Didn't even have a scratch. Strained his back at work, this morning, trying to lift a power-unit cartridge by hand."
     I could believe that. Those things weighed a couple of hundred pounds. Joe Kivelson swore.
     "What's he think this is, the First Century Pre-Atomic? Aren't there any lifters on the ship?"
     Llewellyn shrugged. "Probably didn't want to bother taking a couple of steps to get one. The doctor told him to take treatment and observation for a day or so."

I pulled on a parka and zipped it up and went out onto the deck. Everybody who wasn't needed at engines or controls was there, and equipment was coming up from below—power saws and sonocutters and even a solenoid jackhammer. There were half a dozen floodlights, on small contragravity lifters; they were run up on lines fifty feet above the ship's deck.

     "I doubt it," Llewellyn said. "I was on an exploring expedition down here, once. This is all igneous rock, mostly granite. There aren't many caves. But there may be some sort of natural shelter, or something we can make into a shelter, not too far away. We have two half-ton lifters; we could use them to pile up rocks and build something. Let's make up two parties. I'll take one; Abe, you take the other. One of us can go up and the other can go down."
     The first trunk must have weighed a ton and a half, even after the branches were all off; we could barely lift one end of it with both lifters.

     We could see a blaze of electric lights ahead where the fire must be, and after a while we began to run into lorries and lifter-skids hauling ammunition away from the area. They had a lot of small fork-lifters that were helping close to the fire.
     As fast as they pulled the big skins down, men with hand-lifters like the ones we had used at our camp to handle firewood would pick them up and float them away.

From FOUR-DAY PLANET by H. Beam Piper (1961)

Miles Teg awoke in darkness to find himself being carried on a litter sling supported by suspensors. By their faint energy glow, he could see the tiny suspensor bulbs in an updangling row around him.

The bobbing motions of the dark shapes around him suggested they were descending uneven terrain. A trail? The litter sling rode smoothly on its suspensors. He could sense the faint humming from the suspensors when his party stopped to negotiate the turn of a difficult passage.

From HERETICS OF DUNE by Frank Herbert (1984)

He found the rangers waiting for him and gave his own orders.

“Rolth, you and Fylh get up to that tower. If anyone tries to stop you pull Patrol rank on him It may still carry some weight with the underlings here. Zinga, where did you leave our packs?”

Five minutes later Kartr and the Zacathan gathered the four pioneer packs. “Slip an anti-gravity disc under them,” said Kartr, “and come on.”

With the packs floating just off the floor and easy to tow, they made their way toward the rear of the building. But, as they approached the narrow flight of stair Zinga said led to the roof, they were met by Fortus Kan. He edged back against the wall to let them pass, since Kartr did not halt. But he asked as they went by: “Where are you going?”

“Settling in ranger quarters,” the sergeant returned briefly.

“That one is still watching us,” Zinga whispered as they mounted. “He is none too stout of heart. A good loud shout of wrath aimed at him would send him scuttling—”

The walls were a murky translucent green. And behind them came and went shapes of vivid color, water creatures swimming! Then Kartr saw that it was all an illusion born of light and some sort of automatic picture projection. Zinga sat down on the packs, bearing them under his weight to the floor.

From STAR RANGERS by Andre Norton (1953)

And as he walked, there came a faint but unmistakable whine from the bulky backpack he was carrying on his shoulders.

That pack, indeed, was carrying him — or three-quarters of him. As he forged steadily along the last few feet to his once-impossible goal. Dr. Elwin and all his equipment weighed only fifty pounds. And if that was still too much, he had only to turn a dial and he would weigh nothing at all.

Here amid the Moon-washed Himalayas was the greatest secret of the twenty-first century. In all the world, there were only five of these experimental Elwin Levitators, and two of them were here on Everest.

Even though he had known about them for two years, and understood something of their basic theory, the “Lewies” — as they had soon been christened at the lab — still seemed like magic to Harper. Their power-packs stored enough electrical energy to lift a two-hundred-and-fifty-pound weight through a vertical distance of ten miles, which gave an ample safety factor for this mission. The lift-and-descend cycle could be repeated almost indefinitely as the units reacted against the Earth’s gravitational field. On the way up, the battery discharged; on the way down, it was charged again. Since no mechanical process is completely efficient, there was a slight loss of energy on each cycle, but it could be repeated at least a hundred times before the units were exhausted.

(ed note: according to Luke Cambell's equation, the power packs are storing about 4.9 kilowatt hours. Can lift 113 kilograms 16,000 meters)

Climbing the mountain with most of their weight neutralized had been an exhilarating experience. The vertical tug of the harness made it feel that they were hanging from invisible balloons, whose buoyancy could be adjusted at will. They needed a certain amount of weight in order to get traction on the ground, and after some experimenting had settled on twenty-five per cent. With this, it was as easy to ascend a one-in-one slope (45°) as to walk normally on the level.

Several times they had cut their weight almost to zero to rise hand over hand up vertical rock faces. This had been the strangest experience of all, demanding complete faith in their equipment. To hang suspended in mid-air, apparently supported by nothing but a box of gently humming electronic gear, required a considerable effort of will. But after a few minutes, the sense of power and freedom overcame all fear; for here indeed was the realization of one of man’s oldest dreams.

A few weeks ago one of the library staff had found a line from an early twentieth-century poem that described their achievement perfectly: “To ride secure the cruel sky.” Not even birds had ever possessed such freedom of the third dimension; this was the real conquest of space. The Levitator would open up the mountains and the high places of the world, as a lifetime ago the aqualung had opened up the sea. Once these units had passed their tests and were mass-produced cheaply, every aspect of human civilization would be changed. Transport would be revolutionized. Space travel would be no more expensive than ordinary flying; all mankind would take to the air. What had happened a hundred years earlier with the invention of the automobile was only a mild foretaste of the staggering social and political changes that must now come.

In seconds, the wind had tossed them out over shadowed, empty blackness.

It was impossible to judge the depths beneath them; when Harper forced himself to glance down, he could see nothing. Though the wind seemed to be carrying him almost horizontally, he knew that he must be falling. His residual weight would be taking him downward at a quarter of the normal speed. But that would be ample; if they fell four thousand feet, it would be poor consolation to know that it would seem only one thousand.

He shouted across the wind: “Doctor! Use emergency lift!”

As he spoke, he fumbled for the seal on his control unit, tore it open, and pressed the button.

At once, the pack began to hum like a hive of angry bees. He felt the harness tugging at his body as it tried to drag him up into the sky, away from the invisible death below. The simple arithmetic of the Earth’s gravitational field blazed in his mind, as if written in letters of fire. One kilowatt could lift a hundred kilograms through a meter every second, and the packs could convert energy at a maximum rate of ten kilowatts — though they could not keep this up for more than a minute. So allowing for his initial weight reduction, he should lift at well over a hundred feet a second.

“I’m afraid you’re right — but I’m not sure we can make it, with this wind. Remember — we can’t go down as quickly as we can rise.”

That was true enough; the power-packs could be charged at only a tenth of their discharge rate. If they lost altitude and pumped gravitational energy back into them too fast, the cells would overheat and probably explode.

Five thousand feet above the ground, Harper began to expect the explosion at any moment. They were falling swiftly, but not swiftly enough; very soon they would have to decelerate, lest they hit at too high a speed. To make matters worse, they had completely miscalculated the air speed at ground level. That infernal, unpredictable wind was blowing a near-gale once more. They could see streamers of snow, torn from exposed ridges, waving like ghostly banners beneath them. While they had been moving with the wind, they were unaware of its power; now they must once again make the dangerous transition between stubborn rock and softly yielding sky.

“… still quite young when I realized that there was something wrong with Einstein’s Theory of Gravitation. In particular, there seemed to be a fallacy underlying the Principle of Equivalence. According to this, there is no way of distinguishing between the effects produced by gravitation and those of acceleration.

“But this is clearly false. One can create a uniform acceleration; but a uniform gravitational field is impossible, since it obeys an inverse square law, and therefore must vary even over quite short distances. So tests can easily be devised to distinguish between the two cases, and this made me wonder if …”

From THE CRUEL SKY by Arthur C. Clarke (1967)

First Men in the Moon Cavorite

"Cavorite" is a gravity shield. If you place a sheet of cavorite between an object and Terra's center, the object is no longer subject to Terra's gravity. Cavor's space ship is covered with cavorite roll-up window shades. All the shades are down except for the one facing the planet you want to travel to. The ship will be attracted to the planet; since the attraction of all other planets, moons, and the Sun are cut off.

This of course violates the law of conservation of energy, which is a no-no. But what did you expect from something written in 1901?

     The object of Mr. Cavor's search was a substance that should be "opaque" — he used some other word I have forgotten, but "opaque" conveys the idea — to "all forms of radiant energy." "Radiant energy," he made me understand, was anything like light or heat, or those Rontgen Rays there was so much talk about a year or so ago, or the electric waves of Marconi, or gravitation. All these things, he said, radiate out from centres, and act on bodies at a distance, whence comes the term "radiant energy." Now almost all substances are opaque to some form or other of radiant energy. Glass, for example, is transparent to light, but much less so to heat, so that it is useful as a fire-screen; and alum is transparent to light, but blocks heat completely. A solution of iodine in carbon bisulphide, on the other hand, completely blocks light, but is quite transparent to heat. It will hide a fire from you, but permit all its warmth to reach you. Metals are not only opaque to light and heat, but also to electrical energy, which passes through both iodine solution and glass almost as though they were not interposed. And so on.
     Now all known substances are "transparent" to gravitation. You can use screens of various sorts to cut off the light or heat, or electrical influence of the sun, or the warmth of the earth from anything; you can screen things by sheets of metal from Marconi's rays, but nothing will cut off the gravitational attraction of the sun or the gravitational attraction of the earth. Yet why there should be nothing is hard to say. Cavor did not see why such a substance should not exist, and certainly I could not tell him. I had never thought of such a possibility before. He showed me by calculations on paper, which Lord Kelvin, no doubt, or Professor Lodge, or Professor Karl Pearson, or any of those great scientific people might have understood, but which simply reduced me to a hopeless muddle, that not only was such a substance possible, but that it must satisfy certain conditions. It was an amazing piece of reasoning. Much as it amazed and exercised me at the time, it would be impossible to reproduce it here. "Yes," I said to it all, "yes; go on!" Suffice it for this story that he believed he might be able to manufacture this possible substance opaque to gravitation out of a complicated alloy of metals and something new — a new element, I fancy — called, I believe, helium, which was sent to him from London in sealed stone jars. Doubt has been thrown upon this detail, but I am almost certain it was helium he had sent him in sealed stone jars. It was certainly something very gaseous and thin. If only I had taken notes…

(ed note: Cavor creates a sheet of Cavorite, which immediately causes widespread local devastation on the scale of a tornado strike)

     "But the explosion — "
     "It was not an explosion. It's perfectly simple. Only, as I say, I'm apt to overlook these little things. Its that zuzzoo business on a larger scale. Inadvertently I made this substance of mine, this Cavorite, in a thin, wide sheet…."
     He paused. "You are quite clear that the stuff is opaque to gravitation, that it cuts off things from gravitating towards each other?"
     "Yes," said I. "Yes."
     "Well, so soon as it reached a temperature of 60 degrees Fahrenheit, and the process of its manufacture was complete, the air above it, the portions of roof and ceiling and floor above it ceased to have weight. I suppose you know — everybody knows nowadays — that, as a usual thing, the air has weight, that it presses on everything at the surface of the earth, presses in all directions, with a pressure of fourteen and a half pounds to the square inch?"
     "I know that," said I. "Go on."
     "I know that too," he remarked. "Only this shows you how useless knowledge is unless you apply it. You see, over our Cavorite this ceased to be the case, the air there ceased to exert any pressure, and the air round it and not over the Cavorite was exerting a pressure of fourteen pounds and a half to the square in upon this suddenly weightless air. Ah! you begin to see! The air all about the Cavorite crushed in upon the air above it with irresistible force. The air above the Cavorite was forced upward violently, the air that rushed in to replace it immediately lost weight, ceased to exert any pressure, followed suit, blew the ceiling through and the roof off….
     "You perceive," he said, "it formed a sort of atmospheric fountain, a kind of chimney in the atmosphere. And if the Cavorite itself hadn't been loose and so got sucked up the chimney, does it occur to you what would have happened?"
     I thought. "I suppose," I said, "the air would be rushing up and up over that infernal piece of stuff now."
     "Precisely," he said. "A huge fountain— "
     "Spouting into space! Good heavens! Why, it would have squirted all the atmosphere of the earth away! It would have robbed the world of air! It would have been the death of all mankind! That little lump of stuff!"
     "Not exactly into space," said Cavor, "but as bad — practically. It would have whipped the air off the world as one peels a banana, and flung it thousands of miles. It would have dropped back again, of course — but on an asphyxiated world! From our point of view very little better than if it never came back!"

     "Imagine a sphere," he explained, "large enough to hold two people and their luggage. It will be made of steel lined with thick glass; it will contain a proper store of solidified air, concentrated food, water distilling apparatus, and so forth. And enamelled, as it were, on the outer steel — "
     "But how will you get inside?"
     "There was a similar problem about a dumpling."
     "Yes, I know. But how?"
     "That's perfectly easy. An air-tight manhole is all that is needed. That, of course, will have to be a little complicated; there will have to be a valve, so that things may be thrown out, if necessary, without much loss of air."
     "Like Jules Verne's thing in A Trip to the Moon."
     But Cavor was not a reader of fiction.
     "I begin to see," I said slowly. "And you could get in and screw yourself up while the Cavorite was warm, and as soon as it cooled it would become impervious to gravitation, and off you would fly — "
     "At a tangent."
     "You would go off in a straight line — " I stopped abruptly. "What is to prevent the thing travelling in a straight line into space for ever?" I asked. "You're not safe to get anywhere, and if you do — how will you get back?"
     "I've just thought of that," said Cavor. "That's what I meant when I said the thing is finished. The inner glass sphere can be air-tight, and, except for the manhole, continuous, and the steel sphere can be made in sections, each section capable of rolling up after the fashion of a roller blind. These can easily be worked by springs, and released and checked by electricity conveyed by platinum wires fused through the glass. All that is merely a question of detail. So you see, that except for the thickness of the blind rollers, the Cavorite exterior of the sphere will consist of windows or blinds, whichever you like to call them. Well, when all these windows or blinds are shut, no light, no heat, no gravitation, no radiant energy of any sort will get at the inside of the sphere, it will fly on through space in a straight line, as you say. But open a window, imagine one of the windows open. Then at once any heavy body that chances to be in that direction will attract us — "

From FIRST MEN IN THE MOON by H. G. Wells (1901)

Dark Dominion Magellanium

This is not quite an antigravity metal, but it is related.


      This object was utterly insignificant in appearance. It was a sphere about the size of a number-two garden pea, dull gray in color and possessing a very low metallic luster. Tom let me look at it a moment before he said huskily “That’s the alien substance I found in the uranium pile ("pile" is an obsolete term for nuclear reactor).” His voice trembled from excitement and I wondered if he hadn’t cracked up from overwork. He’d been up all the night before, had worked all day, and now looked as though he planned to keep going another twenty-four hours.

     “Well, what is it?” I said with annoyance.

     He sighed in relief. “I’m glad you ask that. Now I know at least that I’m not imagining it. What is it indeed? Go ahead, examine it. Touch it, feel it, pick it up.”

     I shrugged and started to do as he asked, grasping the small gray sphere in my fingers. To my astonishment I couldn’t budge it. “It’s made a union with the metal of the table top,” I said. “Got a chisel handy? I’ll jar it loose.”

     “Sure,” he said, and there was a note of humor in his voice. “Go right ahead and chisel.” The proximity of the tools on the next bench made me suspect he’d been using them himself before I arrived. But evidently he wanted me to repeat a few of his own experiences, so I obliged him by placing the blade of the chisel against the table at the base of the small mass and giving the chisel a tap with the hammer. The sensation was precisely the same one I’ve experienced hundreds of times when I’m out rock hunting and try to drive a chisel into the face of a stone mountain. You could feel a tremendous resistance. In a mountain you’d expect it, but with an object this small the sensation was positively eerie. I tapped harder and then gave the chisel some really solid blows, annoyed at the thin grin on Tom’s lips. To my relief the stuff moved. I won’t say it came loose from the table because obviously it wasn’t fastened to the table. It rolled with tantalizing slowness about half a turn and lay still again. Quickly I seized it with my fingers and tried to lift it again with the same result as before. It wouldn’t budge.

     “It must be a powerful magnet of some kind,” I said. “Won’t let go of the steel table top.”

     “Then why didn’t it attract your chisel? That’s steel too.” As he spoke, Tom handed me a dish of iron filings and watched as I sprinkled them over the tiny sphere. No result. The iron filings fell like dust and showed no magnetism at all. I bent close to the table and blew them away, and then I noticed that in turning over, the object had left behind it a small but nonetheless definite indentation in the sheet steel of the table top. I began to feel the way Tom looked. He watched me expectantly as he waited for my opinion.

     “Have you weighed it?” I said.

     He nodded. “Measured and weighed it. Hank Kuka helped me move it. Its total volume is slightly more than a cubic centimeter and it weighs approximately two hundred pounds. That’s better than a ton to the cubic inch."

     “Why do you say approximately? Won’t your balance give you an exact weight?”

     He ignored my impatience. “After you weigh it a few times, you’ll use the same word. We weighed it very carefully the first time, but afterwards We couldn’t believe it, so we weighed it again. The second time it weighed slightly more, and that made us try a third time. Still more. I’m going crazy, so I called you. The thing frightens me. Maybe there’s no danger, but I made Gail and Kuka and Fred Clark leave.”

     “How about its size? Have you measured it more than once?”

     “That was the first thing we thought of—that it was growing. But, no. It gets no bigger, just heavier.”

     There was no point in further speculation until owe learned more about the substance on the table. Anything with such density as this stuff possessed could be expected to have other queer properties, and the weight itself— which I’d already experienced—was enough to send chills down my back. The complete unsubstantiality of an hallucination couldn’t have been more startling than the profound substantiality of this object on the table. Such density is difiicult to illustrate by ordinary comparisons. Lead, for example, is generally considered a heavy metal, and one cubic foot of it weighs some 685 pounds. But a quick calculation with the figures Tom gave me showed that a cubic foot of his new element—if it was an element—would weigh three and one-half million pounds! The bit we had on the table was only one-sixteenth of a cubic inch and even its weight was suflicient to dent the steel table top simply by resting upon it.

     But what was it? And aside from its weight, what were its other properties?

     “At least we can give it a name,” I said. “How about Hernandium?”

     “No, thank you,” said Tom. “The discovery may be a big mistake. Let’s call it Magellanium, after the project.” So we called it that.

     “I can’t help the horrible feeling,” he said, “that it may be lying dormant like a time bomb. The atomic tension must be a thousand times greater than in any of the heavy elements we know. And that means the force holding it together has to be greater in the same proportion. If something should disturb the equilibrium—”

     “If that happens we won’t live to worry about it.”

     We gave it every quick test we knew. The lump of Magellanium resisted all acids even though its low luster gave it a metallic appearance. It refused to form a compound with any other element, not even carbon, under any of the conditions we created. Even more astonishing, many of these tests were performed at high temperatures and the Magellanium wouldn’t even get hot. A very slight increase in the temperature of its outer surface was registered, however, which made us think that if it were left in the furnace for a long enough period, it might eventually be warmed through.

     It was nonmagnetic and wouldn’t conduct electricity. Under a high-powered microscope its surface failed to disclose any striations or irregularities. This last fact made me wonder why, then, it gave off any luster at all, so I examined it under a polaroid lens. Again I found nothing distinguishing until a heavy truck passing on the street outside jogged across a drain gutter and jarred the foundations of the building. Not a jar you could feel with your body, but I heard the jolt of the truck while looking through the polaroid, and at the same instant a shimmering wave of iridescence passed over the object I was examining. It endured only a fraction of a second.

     “My God,” I said, “I think it’s a liquid. Pound the table.”

     “Pound the table?”

     “With your fist. Give it a few solid blows while I see what happens.”

     Tom did as I asked and with each blow of his fist the same wave of multicolored light appeared in the microscope. I let him observe while I pounded. This iridescence wasn’t visible with the naked eye, nor with an ordinary lens, but the sudden flash of varigated light could be explained as submicroscopic ripples which in a substance this dense would travel across its surface at atomic speeds.

     “That could also explain the spherical form,” said Tom. “A drop of any liquid as heavy as this would form into a ball. Even small drops of mercury do that. A high surface tension.” He paused, thinking about this, and then went on in sepulchral tones. “Has it occurred to you that what we may have here is a single gigantic atom of some new element? The force holding the protons of an atom together can be treated as surface tension too. My positron bombardment may have filled up all the interstices of space with neutrinos.”

     “There’s no doubt but what your positrons had something to do with producing it because that’s the only new factor you introduced into your experiment. But I won’t say yet that this is a single atom or even a single molecule.”

     “But the incredible weight.”

     It always came back to that. In spite of its other peculiar properties, or lack of properties, the weight was the single quality differentiating it most sharply from any known substance. The psychological effect of this is hard to describe. One might say, “What is so remarkable about its weight? Only two hundred pounds. Only double the weight of a sack of cement.” True enough. But when a man picks up a sack of cement, he expects to grunt a little. Reduce the bulk of two cement sacks to an object the size of an aspirin tablet without altering the weight, and the whole quality of the experience in dealing with it changes. You can’t shake off the belief that it’s fastened to whatever surface it rests upon. Place it in the palm of your hand and it would crush through skin and flesh just as though a fully-grown man with a blunt spike protruding from his heel were standing on your hand grinding down on you. Except that no man would be there—only that pea-sized sphere.

     Tom and Hank Kuka had weighed it the last time just before I arrived, and now Tom and I weighed it again, carrying it to the balance in a basket he’d rigged out of a steel crucible. The spectacle of two strong men straining themselves to transport so insignificant an object was ridiculous. It was as though some giant invisible hand were trying to pull the thing away from us.

     Tom looked at the balance arm and goggled. “Santa Maria! Now it shows a decrease in weight. Maybe it breathes!”

     We tested it for radioactivity again, thinking it might be subject to some periodic change whereby it absorbed particles for a time and then emitted them. Again the results were negative.

     It was only a little after ten o’clock but Tom had been up for nearly forty-eight hours and I’d been up since three-thirty that morning, so I suggested that we get some rest and tackle the problem again the next day. He sadly agreed. So we lowered our sample of Magellanium, steel crucible and all, into a lead casket which was ordinarily used for storing radioactive elements. Use of the casket was purely precautionary because the Magellanium had still shown no activity at all except by changing its weight. Then we bolted down the lid.

     “All right. But it occurs to me we’d better discover some more of it. You’ll need more than a single sample for experimentation.” I took a scratch-pad and pencil from the table and made some rough calculations, and as I did so, the incredibility of the Magellanium returned to me. “This isn’t good,” I said. “From the five tons of concentrate you were using in your experiment, you isolated one cubic centimeter of Magellanium. If that ratio holds good, it will take about eighty-five thousand tons to produce a cubic foot. There isn’t that much uranium ore on the project.”

     My statement made him laugh. “And why do you mention a cubic foot? ]ust because you’re curious to see if it will really weigh over three million pounds? Anyhow, that isn’t the way the thing works. The Magellanium isn’t something I isolated from the uranium pile; it’s something that was created there. I stopped the bombardment to get this one sample, but I think if I continued it, the entire pile might be reduced to Magellanium.”

     Tom was standing in the center of the big room, his hands clasped behind his back, his gaze fixed with intense concentration upon the floor. He straightened with a start when he heard my footsteps and looked at me accusingly. “Have you been in here without me?”

     “No,” I said, surprised at his tone. I glanced around to see what bothered him, looking first for the casket containing the Magellanium sample. It was no longer against the north wall where we’d left it. For an instant I was gripped with the fear that I’d imagined the entire episode and then I saw the casket some twenty feet away against the west wall. “You’ve moved it,” I said. “Why?”

     “I’ve moved it? That’s what I’m accusing you of! I got here about five minutes ago and found the thing shifted.”

     We stared at each other a moment, then at the casket, both of us struck by the absurdity of our accusations. “No one could have moved it alone,” I said. “The casket itself weighs a half a ton. Surely there hasn’t been a gang of men in here without permission.”

     He pointed to the floor at which he’d been staring. "And even so, why would they move it in a curve? Why not push it in a straight line?”

     This was the oddest thing of all. The path the casket had followed from its original resting place to its present position was plainly marked on the floor, which was asphalt tile. The corners of the casket had grooved into git deeply, marking out a series of concentric curves which started from the north wall in a southeasterly direction, veered more and more to the south, and then swung to the west and led up to where the casket was now resting. Curiously, this path of movement had taken the casket beneath one of the laboratory tables where a table leg was sheered off, a steel table leg originally bolted to the floor.

     With unspoken agreement we both stepped to the casket, unbolted the lid and looked in. The Magellanium was still there although it, too, had moved. The steel crucible containing it wasn’t in the center of the casket where we put it but was against the side of the casket next to the wall. lt might have been jarred into that position if the casket had somehow been tilted.

     Tom straightened and returned his attention to the grooves on the floor, his face thoughtful. He got a meter stick and made a few measurements, then looked at me queerly.

     “I’ll answer your last question,” he said. “There’s no ‘why’ about it. No one has been in the laboratory and no human agent moved that casket. Look at the lines on they floor. Every one of those curves is an ellipse—a perfect ellipse. I’ll take some finer measurements later, but just by using my eyes I’ll swear I’m right.”

     There was no argument about this. The curves on the floor were absolutely regular with the points of greatest elongation beneath the laboratory table. Had the general curve been continued past the place where the casket now lay, through the west wall of the room and back around the outside hallway, the casket eventually would have ended up very close to, if not exactly, at the spot where it started. This was merely the observation. Tom’s deduction from it was that no human agent could have moved the casket, and again I felt he was right. It’s difficult enough to draw a perfect circle on the blackboard with a piece of crayon. Except for Michelangelo’s celebrated ability along this line, I don’t think anyone can do it without using a string for a radius. A perfect ellipse, requiring two focal points, is even more diflicult. To think that any person or group of persons could have pushed or dragged the casket in such a path was absurd. Such curves belong to the cosmic forces of outer space or to the microcosmic forces of the atom. However, something had moved the casket. Sometime between ten o’clock the previous evening when we left the laboratory and this morning when Tom entered, some force had been at work.

     I got down on hands and knees and followed the grooves along the floor like a bloodhound on a cold scent, and immediately one more peculiarity became evident. The casket had cut deeply into the floor at the beginning, going all the way through the asphalt tile and scratching the concrete beneath. But as I progressed, the groove became steadily more shallow until at its farthest point beneath the table it was no more than a faint scratch on the surface of the wax. Then it gradually became deeper again until at the point where the casket stopped moving, the tile was once more deeply scored. I pointed this out to Tom.

     “It’s as though the casket became lighter or was subjected to a lifting force for part of its journey and then became heavier again.”

     “I don’t know about the casket becoming lighter,” he said. “But your theory accounts for what we know about the stuff inside the casket.”

     “There was no variation in weight as great as that.”

     “I know. But we didn’t continue weighing it for a full twenty-four hours. We put the stuff to bed a little before ten and went home.” He was still studying the floor and now his eyes brightened. “I keep thinking that with a substance as dense as Magellanium, the ordinary law of gravitation may not apply. Inertial mass and gravitational weight aren’t the same. The reason a lump of lead and a block of wood fall at the same rate of speed is because the inertia of the lead offsets the greater gravitational pull. The block of wood is attracted less by gravity but at the same time has less inertial resistance. The rate of fall is simply the difference between these two forces, and with ordinary varieties of matter this difference is a constant for everything. But with Magellanium—”

     “Yes?” So far he’d said what anyone could say.

     “—the earth turns, but the inertial mass of the Magellanium is so great that it doesn’t want to turn with it. Like a swinging pendulum maintaining a constant position relative to space. It wasn’t the Magellanium that moved; it was the floor moving underneath it—until the casket came up against the wall.” Then he shook his head in annoyance. “That’s no good at all. You and I were able to move the Magellanium. With effort, but we still were able to carry it around. And anyhow, why the curving path!”

     “At least you’ve given me another theory,” I said. “Maybe with Magellanium the inertial mass is so great that it falls far slower than anything else. Maybe the reason we keep getting different weight measurements is because we don’t leave it on the balance long enough. Perhaps it has to sort of settle into place.”

     “At least that’s something we can try.”

     So once more the two of us hoisted the crucible holding the Magellanium out of the casket and onto the balance. My theory was dashed immediately. The balance hadn’t been changed since our last recording, and now the arm lifted abruptly as the Magellanium came down on the platform. It was several grams heavier than at any other time.

     “I’m going crazy,” said Tom.

     “You’ll have company.”

     “We’re getting somewhere,” he told me. “Item one, I think it’s a liquid. Item two, the curves on the floor are not perfect ellipses. Item three, the stuff has continued to lose weight until now it weighs a mere hundred and eighty pounds. Item four, I’m making more of it.”

     “All right. Take them one at a time now.”

     So he did. After my departure that aftemoon Tom and Kuka put the sphere of Magellauium on the press and tried to find out how much pressure it would stand Without crushing. It Wouldn’t crush but it did change shape. Under sixty tons pressure it flattened slightly and became spheroid in shape. Under one hundred tons the flattening was enough to observe With the unaided eye. Then they removed it from the press and it returned to its original shape. They put it under the X-ray to look for resultant lines of strain but could find nothing, for the simple reason that X-rays wouldn’t penetrate it.

     “But only a liquid or a gas could return to its original shape after that much pressure,” said Tom. “And it certainly isn’t a gas.”

     “What happened under still greater pressure?”

     “We ran into some kind of law of diminishing returns whereby it took doubled amounts of pressure to bring about any further flattening. At peak pressure the blocks were dented without hurting the Magellanium. We were pretty nervous doing it. I still think we may be dealing with a gigantic atom, and no matter how stable it seems, We might accidentally split it.”

     I went over the computations Gail had made that afternoon from the measurements taken by Hank Kuka. He’d located the two focuses for the curves on the floor and had then measured a series of radii. The result showed that instead of an ellipse, the general path was a section of a spiral.

     “That’s right,” said Tom. “Of course that lead casket isn’t exactly a precision instrument when it comes to drawing curves, but Hank could be several millimeters ofi and the result would still be valid.”

     Actually what this result showed was that the curves on the floor—supposing they were drawn on a large surface with no intervening walls—would never have returned quite to their starting place but would have inscribed a series of ovals like those we used to make in grammar school when we were learning penmanship. Except that these would have been exactly backward from the kind on paper, moving from right to left in reverse rotation. Toward the east.

     “It suggests some connection with the rotation of the earth and the movement of the earth around the sun,” said Tom. “I was pretty worried when Osborn left, but I’m beginning to calm down. We can’t discover everything in a single day or even in a single year but gradually we’re accumulating facts. If I stay on at the project after the launching, this will give me plenty to work at.”

     I glanced at the clock. “Hell, Tom, We’ve been talking and missed the 10:15 weighing ceremony. Let’s do it now.” I looked at him for assent and then came to my feet, shocked by the expression of wild consternation on his face. He was staring past my shoulder toward the north wall, his finger extended.

     “My God, Ambert! Look!”

     I whirled, chilled by his tone, my scalp pringling. My feelings weren’t altered by what I saw. There, was no doubt about it. That thousand pound casket with the incredible weight of the Magellanium inside it was sliding ponderously toward us across the floor!

     For a full ten seconds neither of us moved while we watched, unable to believe, yet forced to believe by what we saw. The actual motion of the casket was so slow that it might have escaped notice for some time, but what couldn’t escape notice was the fact that it was now at least two feet out from the wall where it had been placed. Obviously it had been sliding forward at its weary glacial speed for quite a while before Tom noticed it. The sloth-like pace encouraged us to walk forward and kneel down for closer inspection.

     At this range the motion was easily apparent. A garden snail could have just about kept up with it. Curiously, it was almost silent. By bending close and not breathing, you could hear the faint crackling of grit being crushed against the floor but the forward edge and corners of the casket plowed across the asphalt tile at such a tedious pace that the fibers were crushed before they had time to snap. The previous scoring was still on the floor and the new lines were being grooved parallel to them but not exactly over them because the casket hadn’t been placed in its exact former position to begin with.

     A vast amount has been written about the precision with which scientists work, and from reading about them one is likely to get the idea that every experiment is circumscribed by a host of delicate gadgets which record and control every phase of the operation. This certainly wasn’t the case now. In the face of something new it’s often the chance observation rather than intent which leads to discovery. Radium was discovered through its effect upon a photographic plate left accidentally in its vicinity; Pasteur grasped the idea of vaccination after his chief critic unwittingly performed the services of a guinea pig for him; Galileo formulated the law of falling bodies by watching a swinging pendulum, and Archimedes allegedly recognized the principle of specific gravity while sitting in a public bath. In spite of these brilliant examples from the past, Tom and I watched the moving casket and failed to grasp any principle at all. But we did begin to putter.

     I placed my foot in front of the thing to see if I could slow it down or stop it. I couldn’t. The pressure against the side of my shoe increased relentlessly until I found I was being pushed along too. I got down on my knees and put my shoulder against the casket with the same result. Then we unbolted the lid, removed it, and looked in.

     The sample of Magellanium was still lying in the little steel crucible but the crucible itself was now pressed tightly against the forward end of the casket. We debated the advisability of removing it and decided not to. It seemed of more immediate value to observe the full course of the casket’s journey Without doing anything to disturb it. But because the Magellanium was obviously in a different state now from any previously observed, I made another test for radioactivity. Still negative.

     Meanwhile Tom equipped himself with a meter stick and a stop watch so he could determine the speed with which the casket was moving.

     He’d finished his preliminary measurements and ran the calculations on the machine. His result, in ordinary language, showed that the casket was moving at the rate of 7.5 feet per hour. By measuring its distance out from the wall, he calculated that the motion must have started at approximately 10:06 P.M.

     “That’s providing the speed is constant,” he said. “I don’t know that yet. There may be a gradual acceleration.” This was the next point he wanted to determine so he kept on clocking the speed at one-minute intervals. I was more interested in the direction of the motion. The fact that it followed a path identical in pattern to the one of the previous night proved that no random force was at work. The power that moved it before was still operating in exactly the same way. The Magellanium— and we could not doubt that the Magellanium was the cause of the phenomenon—was being attracted or repelled by some agency which had a fixed location either upon the face of the earth or elsewhere, but all I was able to determine immediately was that it had no connection with the magnetic poles of the earth. I wondered if there might be something in one of the other buildings on the project itself to provide an explanation. In that case, however, the casket should move in a straight line.

(ed note: The scientists are called away, and they forget to put the lid on the box. When they return the Magellanium sample has vanished)

     Tom finished the thought, speaking slowly as though unwilling to voice a seemingly impossible conclusion. “Then perhaps it moved up the side. There being no lid to stop it, it escaped. But where?”

     We returned to the casket and examined it thoroughly. In spite of its great weight, the casket wasn’t a huge box. The walls and floor were about three inches thick but the total volume of lead was less than two cubic feet. If it had been shoved across the floor empty, its own weight was suflicient to score the floor deeply. Therefore, in spots where it failed to make deep scratches, the only possible conclusion was that a force almost equal to the weight of the casket was lifting it. Such a force couldn’t be generated by the lead, a substance with which we were well acquainted. The unknown factor was the Magellanium. But in order to lift the casket, the little sphere of Magellanium would have had to move up the side of the casket until it pressed upward from within, against the lid. If you imagine a matchbox containing a small lump of iron being acted upon by an exterior magnet, you get a fairly decent analogy. As the iron moves toward the magnet, it draws the box along with it. Place the magnet above the box and you can lift the whole thing. If the box has no top on it, the piece of iron will come out. Then suppose that your magnet is invisible, and you have quite a mystery on your hands.

     This was our mystery. Whatever attracted the Magellanium was like no magnet known on earth, and it was definitely invisible to us so far. However, the constant speed at which the casket had been moving, the regularity of its path across the floor, and the periodic change in the weight of the Magellanium all pointed forcibly—almost conclusively—to a single controlling principle. The same principle, whatever it was, should also account for the disappearance of our sample.

     Our close inspection of the casket seemed to confirm Tom’s theory. On the interior of its forward wall the relatively soft lead bore two very shallow grooves extending in straight lines from near the casket floor to the top. One of these proved to be slightly deeper than the other. I examined the lid of the casket and discovered what we hadn’t noticed before—a slight indentation on the underside of its lip. When the lid was put in place, this indentation fitted exactly at the top of the deeper groove. We concluded, therefore, that this deeper groove had been made by the Magellanium during its first night in the casket. It had moved upward until stopped by the lid, then at a later time had moved down the groove again into the steel crucible. The first groove was deeper because the Magellanium had traversed it twice.

     There was no second indentation in the lid to correspond with the second groove, nor did this groove quite terminate at the upper edge of the casket wall. It seemed instead as though the Magellanium had rolled over the edge as though pressing at an angle upward and away from its container. And where was it now—?

     Tom suddenly knelt beside the casket, sighting across its top in the direction the casket had been moving before the Magellanium vanished. He exhaled a long breath of satisfaction mingled with amazement and pointed toward the south wall. At first I didn’t know what he was pointing at. Then I saw it. Between two windows, the white plaster was punctured by a small dark hole. It was about six feet above the floor and was circular. It had a diameter the same as our sphere of Magellanium and had been punched by something moving with such terrific momentum that the plaster around it wasn’t even cracked. A forty-ton drill press couldn’t have done a neater job.

     We said nothing. I knew as well as I know anything that our vanished Magellanium had made that hole in the wall, but I couldn’t bring myself to say it because then I also had to believe that the Magellanium left the casket at an upward inclination of about fifteen degrees and literally floated through the air until it struck and penetrated the wall. Or was float the right word? We hadn’t seen it vanish and it may have been going at bullet speed or faster. The cleanness of the hole indicated that.

     I took a glass rod from the supply closet and thrust it into the hole. It was a tight fit but the rod went clear through the eight inch thickness of wall without cracking.

(ed note: Tom made some new samples and sends them to Ambert. In another room Ambert examines them.)

     One thing was new, however. Previously we’d had only a single sample of Magellanium and now I had five; previously the single sample had appeared utterly inert in regard to its immediate surroundings but now it was evident that my samples eere not inert in relationship to each other. They attracted each other. But to what degree? I made certain that the steel boxes themselves weren’t magnetized, by testing them on the iron frame of my cot. This metal had no influence upon either the box or the grain of Magellanium inside it. I then placed two boxes on the concrete floor about six inches apart and watched. The result was uncanny. No sooner did I take my hands from the boxes, than they moved toward each other. Their speed was much faster than that of the lead casket in the laboratory. When they came together, they stopped. I lifted the lids carefully and looked in. The bits of Magellanium were as close to each other as the intervening sides of the boxes permitted, each sample pressed tightly against the side of the box as though they were striving to penetrate the steel and reach each other.

     I tried the experiment again, starting the two boxes from a foot apart. Again they came together. I estimated a distance of two feet and tried again. The same result. The force of the attraction seemed to be unaffected by distance. I had dramatic proof of this when the other three boxes which I’d left on the cot suddenly fell to the floor where all five came together in a group. For a moment I was terror—stricken lest the fall had jarred the box lids loose, but all the samples were still safe. The grouping gave me another idea. Arranging four of the boxes in a row, I put my foot on them to hold them in place, then scooted the fifth box across the floor toward the opposite wall about twelve feet away. It was as though a strand of strong elastic were attached to the box. It slid away some six or eight feet, slowed, and then came snapping back. The distance was such that it gathered momentum on the return and struck the boxes beneath my foot forcibly. When I peered into it, I discovered that the grain of Magellanium had made a deep dent in the side of the box. When the box stopped upon striking the others, the momentum of the Magellanium had almost carried it through the steel wall. With a little greater momentum, it would do so. This showed me also that the speed wasn’t constant; there was a definite rate of acceleration.

     I then placed my stick on the floor with the mid-point against the iron leg of the cot. Four of the Magellanium samples I placed at the opposite end of the cell, piling the cot mattress on top of them to hold the boxes in place and keep them from joining the fifth box which I carried back to my measuring rod. This box tried very hard to join the others but I could prevent its doing so by laying it on the floor behind the measuring stick while I held on to the other end of the stick to keep the box from shoving it aside. Between my hand and the box, the leg of the cot acted as a fulcrum and gave me leverage to hold the box in place.

     As you see, I had constructed a simple horizontal balance, and next it was necessary only to find a weight other than my hand to use in determining the strength of the attractive force. My poverty of instruments was such that I finally used my shoe. I took it off and set it on the floor against one end of the stick. The box containing the Magellanium was at the other end on the same side of the stick and the cot leg halfway between the two but on the opposite side of the stick. As the Magellanium pressed forward, the stick would pivot against the cot leg and force the shoe to move in the opposite direction.

     My object was to discover just how strong the moving force of the Magellanium was. This I could do by applying the simple rules of the lever. When my cot leg—the fulcrum—was placed midway along my lever—the chair round—the Magellanium moved the shoe easily. So I continued to shift the lever along the fulcrum, giving the shoe greater and greater leverage until the shoe finally balanced the force of the Magellanium at a point where three-fourths of the lever was on the side of the shoe. The force with which this particular bit of Magellanium was attracted toward the others was, therefore, three times the inertial weight of the shoe.

     With this much achieved I verified what Tom told me in his note, even though it reduced my number of samples. I opened two of the boxes and dumped the contents of one into the other. The tiny spheres of Magellanium merged with a speed that almost cost me the observation. They met—and then there was one! ]ust as two drops of water or two drops of mercury will meet and merge, so had these two bits of Magellanium. What remained was a single sphere larger than the others. It had doubled in weight as well as in size.

     With the doubled sphere of Magellanium I returned to my lever to find out if the force of attraction had also doubled—as it should if Magellanium obeyed a law similar to those governing gravitation and magnetism. I expected its force to be now six times the inertial force of the shoe. I was wrong. The force of the Magellanium was now nine times the Weight of the shoe. In short, by doubling its mass I had squared the force of attraction. Crude as my measurements were, I had to believe this because it explained why our original sample of Magellanium, larger than any now in my possession, had been able to move a lead casket five times its weight, whereas these tiny specimens balked at moving a weight equal to themselves. But if I should increase their mass a hundredfold, the attractive force between them would be increased by ten thousand!

     I had reduced my samples to three and now I determined to reduce them still more. What was evident to me, if not to the others, was that some external force was now acting upon the Magellanium, a force which had come into play after Humphrey arrived. I stood up with the box containing the enlarged sphere of Magellanium in my hand.

     “Watch closely,” I said to Humphrey. “This is something I’ve never seen myself, and I can’t guarantee the result, but I believe I’m going to show you what happened to the sample of Magellanium we wanted to show you last night.” The pull of the Magellanium was powerful as I tilted the box toward the southeast wall. The weight was still there but the weight was no longer directed downward. It didn’t take much of a tilt. The little sphere started rolling up the side of the box as soon as the angle became less than ninety degrees to the direction of its attraction. Then in the instant that it cleared the edge of the box, it was gone. For an inch, perhaps, it was visible, and then the speed was too great to see it. We heard only the snick as it struck the wall and saw only a flake of plaster fall to the floor to indicate Where it had vanished. But in that instant I had leaped across the room and placed my eye against the hole in the wall, cupping my hands around it to shut out the light of the cell. It was a true direction this time—east by southeast. And I saw it —the destination!

     You have seen it too. Virtually every man and woman on earth has seen it. Any clear winter night will do. For only an instant the object in the sky was visible and then I could see it no more. The earth turns, and the hole through which I was peering was a foot long and no more than a sixteenth of an inch in diameter. Of the heavens it let me see no more than a second of arc at a time and the second had passed. I saw in this the means of proof for the theory that had leaped to my mind. I still possessed my original enlarged sphere of Magellanium and now, despite the fact that I was exhausting my supply, I opened the lid of this box, tilted it, and let the second sphere go. Again the bulletlike departure at the low upward inclination, then the faint snick as it passed through the wall and a second hole near the first. I was there sooner this time and once more peered through the thin aperture into the night. And again for an instant it was there. Then I was sure. Then I knew. Regardless of the turning earth, the released Magellanium always headed for a certain star in the sky. That star had risen above the eastern horizon not more than fifteen minutes earlier and still hung low in the southeast, but there was no mistaking the cold brilliance of Sirius, the Dog Star. I knew then how Archimedes felt when he leaped from his bath crying “Eureka!

     I said that the Magellanium was moving toward Sirius, drifting at an unknown speed across those billions of miles toward a star close to nine light years distant. The implications of this statement are misleading unless you’re familiar with the peculiarities of the Dog Star, which is not the single blazing point of light it appears to be, but is actually a double star, of which thousands are known to exist in the universe. But the duality of Sirius is unique. It is composed of the star we see with out eyes and of another star so faint in comparison with the visible giant that only the most powerful telescopes can reveal its presence and then only when its position is most favorable. It was not the telescope, however, which first discovered this companion star; its presence was deduced because of certain perturbations in the orbit of the visible star—perturbations which could be explained only by the existence in the near proximity of some unseen mass with a high gravitational attraction. A search for such a mass was then instituted by astronomers and resulted in the discovery by Alvan Clark in 1862 of the faint companion.

     For years this companion star was the riddle of the heavens. The visible Sirius has some two and one-half times the mass of our sun and gives out twenty-eight times as much light. But calculations based upon the luminosity of the companion indicated that its size couldn’t be much greater than that of the earth. For such a relatively small body to affect the orbit of Sirius to the degree known from observation seemed impossible, and it was assumed the calculations regarding the size of the companion were erroneous until spectroscopic studies made by Adams in 1914 and again ten years later confirmed original results. The almost unbelievable conclusion resulting from these studies was that a mass almost equivalent to that of the sun was squeezed into a volume only slightly larger than the earth. If you increased the mass of the earth 200,000 times without increasing its size, you’d have a body similar to this faint companion of Sirius. It’s known as a white dwarf star. Its density is some 61,000 times that of water and a sample of it upon earth would weigh close to a ton per cubic inch. For years men have speculated upon the characteristics of matter at such enormous density. Now abruptly many of these characteristics were revealed to me by the realization that Magellanium was nothing more nor less than ordinary matter, stripped of its electrons by positron bombardment and compressed into the same state as the matter which composes the white dwarf of Sirius.

     It was the white dwarf, not the visible component, toward which the Magellanium was being drawn, and the fact of this afiinity of Magellanium for that distant star was proof enough of the direct relationship between the two. Magellanium was attracted only by Magellanium. There was more evidence if any was needed. The movement of the casket—how logically that fell into place! During that part of the day when Sirius was below the horizon, the force of attraction pulled the casket downward against the earth and so the casket couldn’t move. But as the turning world brought Sirius above the horizon, the bulk of the earth no longer stood between the Magellanium and its distant archetype; then the Magellanium began moving toward the point on the horizon where Sirius was rising. Because the Magellanium had to drag the heavy casket with it, the movement was slow, and meanwhile the earth continued to turn. Sirius continued to rise high in the sky and as the Magellanium attempted to follow the star, its direction gradually shifted from an easterly one to a southeasterly one, then to south, to southwest, and to west as Sirius set. Then the casket was immobile once more. This was the explanation for the changing weight of the Magellanium. What we had weighed wasn’t the strength of the earth’s gravitational attraction but the strength of the attraction toward Sirius. As long as the attraction was downward, the weight seemed great. But when Sirius was in the sky and the attraction was correspondingly upward, there was no gravitational weight at all. There was only the inertial mass of I the stuff itself trying to reach its master in the sky.

     But why hadn’t the sample of Magellanium penetrated the side of the lead casket as it did the wall? Because while it was inside the casket, it had no momentum. If you place the point of an arrow against a pasteboard box and shove, you’ll find that you move the box. But stand back ten paces and fire the arrow at the box with a bow, and the arrow will go right through it.

     I realized only that with Magellanium the classic law of gravitation didn’t work, that to describe the nature of its force I would have to paraphrase the law of gravitation thus: Every particle of Magellanium in the universe attracts every other particle of Magellanium in the universe with a force unaffected by the distance between them and directly proportionate to the square of the mass.

     But except for the samples produced in Tom’s laboratory and the white dwarf itself, was there actually any other Magellanium in the universe? There had to be. There were other white dwarf stars in our galaxy and in the far-flung island universes. Were they all rushing toward each other across those incomprehensible interstellar distances? Upon What distant day would they meet? Would the impact of their meeting be suflicient to shatter the stability of their condensed matter and release the atoms from constriction? In such a cosmic explosion whole new universes might be born—perhaps had been, perhaps would be born again.

     Tom hadn’t wasted any of his particles of Magellanium and now had hundreds of specimens of buckshot size, each carefully separated from the others by its own container.

     “If each particle of Magellanium is attracted by the white dwarf,” he said, “why do certain particles repel each other?”

     “But they don’t! None of those you sent me did.”

     “Ah, but later I began to produce other specimens with a different result. Certain particles attract each other and others repel. On that basis I’ve been able to place them into different groups. On this side of the room are specimens of the kind I sent you—all mutually attracted to one another. I now call this type Magellanium A. But over here on the other side of the room are more specimens exactly the same in every respect except one—they are repelled by Magellanium A and are attracted only to each other. This group is Magellanium B. And so with the third group, Magellanium C—particles attracted to each other but repelled by either of the other two groups. If Magellanium A belongs to the white dwarf of Sirius, to what do the other groups belong?

     “It should be simple to find out,” I said. “Release a few particles, if they’re in the moving state, and calculate their direction. I was lucky in that Sirius is visible at this time of year. But there are stars in the daytime as well.”

(ed note: The Magellanium was accidentally discovered at the Magellan project, whose purpose was for the US to orbit a space station called the "Black Planet". This was loaded with nuclear warheads and would allow the US to dominate the entire world. A spy leaks this info, and the other nations are quite upset about it. An enemy air strike destroys all the rocket fuel. Ambert jury rigs a way to get the space station into orbit using Magellanium.)

     I sketched out on several sheets of drafting paper the details of a mechanism I was going to need. Then I called Walker Hedgerow, the superintendent of the machine shop, and told him to come to my office.
     He arrived shortly and I showed him my rough drawings, explaining to him what I Wanted and how it had to function. I needed a circular metal plate of a size that Would fit the base of the “Black Planet’s” cone. The plate had to contain several thousand individual cells—something like the plate of a waffle iron on a magnificent scale—each cell about a cubic centimeter in volume. These had to be divided into three groups with some sort of lid arrangement which would make it possible to open all the cells in any given group simultaneously.
     Hedgerow looked my drawings over and after finding out how the mechanism was supposed to work, made a number of corrections which simplified it a great deal He wanted to know how soon I had to have it.

     “The sooner the better. Three hours?"

     He whistled and shook his head discouragingly. Then he said, “How strong do the walls of these cells have to be?”

     “Strong enough to contain a pressure of about fifteen pounds each. Even thin metal will do that. The plate will have to be stronger.”

     “The plate is no trouble. We can cut it out of sheet steel. But the cells —" He thought a moment. “There’s some honeycomb grating in the shop. If I put a layer of that across the plate and welded it down, you’d have about —” He paused to calculate the number of perforations per square foot in the grating and multiply it by the area of the plate. “About one hundred and fifty thousand cells. Is that enough?”

     “More than we need, but if that’s the simplest, use the honeycomb grating. And do it fast.” Hedgerow departed with the plans and I called Tom. “Are you still in production?”

     “Still going. I’m getting a good-sized inventory. And I think I’ve located the source of attraction for B and C. B is near Antares in Scorpio, very active right now. If I live so long I’ll train a telescope on that spot some warm summer night and see if I can become the discoverer of a hitherto undiscovered white dwarf. The origin of the C attraction is in the north so close to the nebula of Andromeda that I’m wondering if that isn’t where it comes from. Seems incredible. Half a million light years away.”

     “How much of the stuff have you?”

     “I’ve been too busy to count but I know we’ve had to use everything in the place for containers to keep it separated. Clark and Kuka are both working with me.”

     “I’ll be with you soon, then.”

     I telephoned Aaron at the space ship and told him to drain the cone of the “Black Planet” of what little propellant it contained.

     Through trial, error, and growing understanding Tom had evolved a production system so that his laboratory looked less like a place for experimentation than a factory. The consumption of uranium concentrate was immense. It was being hauled up from the reduction plant in carload lots and fed into the vault for positron treatment. Hank Kuka had taken over supervision of this end of the work while Fred Clark Was engaged in removing the Magellanium from the vault at regular intervals. By periodically stopping the process before the Magellanium had time to coalesce into a single sphere, Clark was able to remove it in buckshot-size beads which were comparatively easy to handle, because their attractive force was seldom over fifteen pounds.

     Tom was now getting Magellanium B again and had reached the conclusion that the type of Magellanium produced was determined by the position of the earth relative to the various white dwarf stars. Although the attractive force of the stars didn’t seem to be changed by any barrier he could interpose in his laboratory, he believed that the bulk of the earth itself was sufficient to interrupt, partially at least, the strength of the attraction. As a result, the Magellanium produced at any given time corresponded in type to the white dwarf then in the sky. This was only theory and failed to account for a number of peculiarities which it was impossible to investigate now. We were like doctors in possession of a serum whose effectiveness was still unproved but which we must use anyway in the hope that its use would bear out the promise of the laboratory.

     The three types of Magellanium were separated from each other by as great a distance as the laboratory permitted. The problem of differentiating the three types was the easiest to solve of any problem yet presented by the stuff. As he brought each fresh batch from the vault, Clark had only to test it against the supplies already stored in the laboratory. C would attract only C; B would attract only B; A would attract only A, and each would repel the other two types.

     I stopped Tom in his work long enough to help me check the set of equations which had been Osborn’s last task on earth. Briefly, Osborn’s problem was this: Was it possible to treat the three different directions of force operating on the three different types of Magellanium as vectors forming three sides of a triangle? What then would be the directional force of the triangle as a whole? As stated, the problem is purely one of mathematical convention, but it enabled him to arrive at a general formula whereby he could predetermine the single resultant from any given juxtaposition of the three forces. This was possible because of the dual nature of the force—that is, each type of Magellanium Was not only attracted toward its white dwarf prototype but was repelled by the other types of Magellanium. Osborn had been uninformed of the relationship between the Magellanium and the white dwarf stars. He was aware only of the opposing forces in the Magellanium itself. His equations were generalizations from which the solutions to specific problems could be deduced. The answer to our specific problem, based on the equation that the force of the attraction was proportionate to the square of the mass, showed that we needed a sphere of Magellanium A eleven inches in diameter to generate the power necessary for our purpose.

     Tom didn’t have that much Magellanium A yet. He had hundreds of tiny specimens but their total volume was so far inadequate. He was producing more constantly, however, so I arranged for trucks to start carting what was already on hand down to the “Black Planet.” Then I went down to the space ship myself.

     The cone of the ship had been drained, and now I set a gang of men to work rearranging the partitions between the fuel tanks. This cone, as I’ve explained, rested on top of the ship directly above the hollow core—like the hole in a spool of thread—through which the rocket thrust was intended to go. There no longer being any rocket fuel, the core and cone were cleaned completely, a task assisted by the fact that everything in these sections, including the cone itself, was designed to be released once the “Black Planet” reached the free-flight orbit.

     Walker Hedgerow meanwhile arrived with the plate I’d ordered. It looked like nothing so much as a great circular piece of honeycomb with the honey removed from the cells. We moved it beneath the ship and then up through the core to the base of the cone, where it sealed the cavity completely. Here it was fixed in place. While the gangs of men worked, I joined Aaron in the office inside the ship, gave him a copy of Osborn’s equations and explained my entire plan. It was so hypothetical in nature and so completely unconfirmed by any prior tests that I found myself getting argumentative while I talked, as though I still had to convince myself. He listened attentatively—even absorbedly—to what I was saying, and then made me stay with him while the two of us went over Osborn’s equations.

     “My hope is this,” I told him. “The ship itself isn’t dependent upon the launching power once it gets into space. It has its own engines to put it into rotation and is entirely self-contained. If there Were a way to catapult it beyond the reach of gravity, that would be just as satisfactory as pushing it up there with rocket fuel. The important thing is to get it there—the right altitude and the right speed. Then you release the cone just as in the original plans.”

     He looked at me curiously for several seconds, then turned back to the equations which lay on the desk before him. “But don’t you understand?” he said quietly. "With these you can actually navigate. It’s so simple you can calculate a course with a slide rule. And Magellanium isn't like rocket fuel; it doesn’t burn up. What would happen if I don’t release the cone?”

     The possibility startled me. “God only knows. It’ll be loaded with three types of Magellanium trying to go in three different directions. As you say, those equations show you how to control it; that’s why I had Osborn do the work. But you’ll do better to watch your speed indicator and altimeter and release the cone just as though you were using rocket fuel. After that your operations will be familiar.”

     The Magellanium had continued to arrive from the laboratory in trucks, was carted up through the body of the ship by elevator and through the hatchway into the cone, Where men were putting it into the cells. Magellanium A went in first because it was heavy and inert at this hour. One third of the cells received a grain of it and then this section was covered tightly. Magellanium C went in next, and then Magellanium B, which by this hour had become inert again. All were sealed into the cells in three difierent sections.

     Tom arrived to supervise the rest of the work and told me the vault was producing Magellanium A again, influenced perhaps by the nearness of Sirius to the horizon. Menu from the engineering staff were inside the ship, making additions to the mechanism by which the cone was to be released so that the same mechanism could control the lids to the three cell sections containing the Magellanium.

     What we had to have was one sphere of Magellanium A larger than the others, a sphere large enough to attract and absorb all the other A particles. By absorbing them, this sphere would grow, and as it grew, the attraction between it and the White Dwarf of Sirius would increase according to the square of the mass. It had to be type A because that type belonged to the White Dwarf of Sirius, and this would be the next of the dense stars to clear the eastern horizon. It was due, in fact, at 10:01 P.M. but had to be given time to climb into the sky or else all our Magellanium would move off at a tangent to the curve of the earth’s surface, and if the “Black Planet” were attached to it, the ship literally would be dragged across the surface of the ground for a long distance before it could be pulled into space. To achieve an angle of inclination which would carry the ship upward and clear the hills bordering the valley, we would have to wait until 10:27.

     The making of the sphere was a simple process and one I’ve already described. Small particles of Magellanium A were permitted to come together. They joined just as drops of liquid join, and so the sphere grew. The pull was still downward and we were able to check the weight on the balance as we made it. Tom’s original specimen of Magellanium had tipped the balance at two hundred pounds at the peak of its downward attraction. We built this one up to twelve hundred pounds and still it was little larger than a child’s marble. But that was enough. Our entire apparatus was already upon a dolly which we moved out of the laboratory and onto a waiting truck. We climbed into the rear of the truck with it and started off.

     We reached the “Black Planet” and drove under the protection of its body where red bulbs glowed through the darkness to mark the locations of entrances and elevators. A waiting crew moved the Magellanium into an elevator. Tom and I followed, and we ascended quickly through the entire body of the ship to the cone, where block and tackle were waiting to lift the last of the Magellanium through the hatchway. The honeycomb plate with its myriads of particles was below us, its lid firmly in place, but I could hear the rustling movement of the A particles as we moved our marble-sized sphere into place beneath the apex of the cone. Here it was once more hoisted upward and secured in a cell at the very peak of the cone.

(ed note: The families of the project team have been sheltering in the Black Planet until launch time. But at the last minute, instead of sending the families out, Aaron launches the ship into space while Ambert watches helplessly outside.)

     I was aware also of the moment when he moved the lever labelled A. Knowledge came with a sound like a giant swarm of bees as the particles of Magellanium A were released from their honeycomb cells and swarmed upward to join the larger sphere of Magellanium at the apex of the ship’s cone. A second—two seconds—the angry hum lasted while the sphere must have grown from the size of a marble to the size of a large crystal ball. It determined its own future. The square of the mass. The Weight of the “Black Planet” was no longer enough to stay it in its blind impulse to drive through space toward the White Dwarf of Sirius.

     The ship moved! How colossal is the vanity of man! For in that instant I forgot my loved ones in the sense of triumph that overwhehned me. Above my head the door upon which I pounded receded. Around me the pedestals quivered and groaned as the weight they had borne so long lifted upward. Several pillars fell, pulled sideways by the oblique course the ship was taking toward the bright star near the horizon. Then I was alone, kneeling at the top of a stairway that led to nowhere. Drifting away from me through the pallid night on its silent course toward infinity was the majestic bulk of the “Black Planet,” drawn like a moth toward the light by the power of Magellamum.

(ed note: Instead of becoming an orbital nuclear bomb dispenser, Aaron decides to fly the ship and the families to another star system and colonize the galaxy. The plan was to jettison the nose cone containing the Magellanium when the ship reaches orbit. Aaron keeps the cone, and uses the three types of Magellanium to steer the ship.)

From DARK DOMINION by David Duncan (1954)

What Goes Up

This is a story by Sir Arthur C. Clarke for his collection Tales of the White Hart (a selection of scientific shaggy-dog stories). It is a tall tale, but contains a bit of scientific truth.

     "You'll all recollect, I'm sure, the scientist Cavor in Wells's First Men in the Moon, and the wonderful gravity-screening material Cavorite he discovered?"
     "I'm afraid dear old Wells didn't go into the question of Cavorite very thoroughly. As he put it, it was opaque to gravity just as a sheet of metal is opaque to light. Anything placed above a horizontal sheet of Cavorite, therefore, became weightless and floated up into space."
     "Well, it isn't as simple as that. Weight represents energy — an enormous amount of it — which can't just be destroyed without any fuss. You'd have to put a terrific amount of work into even a small object in order to make it weightless. Antigravity screens of the Cavorite type, therefore, are quite impossible — they're in the same class as perpetual motion."

(ed note: the point being that the Cavorite expends no energy when it degravitationalizes something. However, as we shall see, it is perfectly permissable to degravitationalize something provided you pay the horrific energy cost)

     "Now, our Australian Dr. Cavor wasn't searching for antigravity, or anything like it. In pure science, you can be pretty sure that nothing fundamental is ever discovered by anyone who's actually looking for it — that's half the fun of the game. Dr Cavor was interested in producing atomic power: what he found was antigravity. And it was quite some time before he realised that was what he'd discovered."
     "What happened, I gather, was this: the reactor was of a novel and rather daring design, and there was quite a possibility that it might blow up when the last pieces of fissile material were inserted. So it was assembled by remote control in one of Australia's numerous convenient deserts, all the final operations being observed through TV sets."
     "Well, there was no explosion — which would have caused a nasty radioactive mess and wasted a lot of money, but wouldn't have damaged anything except a lot of reputations. What actually happened was much more unexpected, and much more difficult to explain."
     "When the last piece of enriched uranium was inserted, the control rods pulled out, and the reactor brought up to criticality — everything went dead. The meters in the remote-control room, two miles from the reactor, all dropped back to zero. The TV screen went blank. Cavor and his colleagues waited for the bang, but there wasn't one. They looked at each other for a moment with many wild surmises: then, without a word, they climbed up out of the buried control chamber."
     "The reactor building was completely unchanged: it sat out there in the desert, a commonplace cube of brick holding a million pounds' worth of fissile material and several years of careful design and development. Cavor wasted no time: he grabbed the jeep, switched on a portable Geiger counter, and hurried off to see what had happened."
     "He recovered consciousness in hospital a couple of hours later. There was little wrong with him apart from a bad headache, which was nothing to the one his experiment was going to give him during the next few days. It seemed that when he got to within twenty feet of the reactor, his jeep had hit something with a terrific crash. Cavor had got tangled in the steering wheel and had a nice collection of brusies; the Geiger counter, oddly enough, was quite undamaged and was still clucking away quietly to itself, detecting no more than the normal cosmic-ray background."
     "Seen from a distance, it had looked a perfectly normal sort of accident that might have been caused by the jeep going into a rut. But Cavor hadn't been driving all that fast, luckily for him, and anyway there was no rut at the scene of the crash. What the jeep had run into was something quite impossible. It was an invisible wall, apparently the lower rim of a hemispherical dome, which entirely surrounded the reactor. Stones thrown up in the air slid back to the ground along the surface of this dome, and it also extended underground as far as digging could be carried out. It seemed as if the reactor was at the exact centre of an impenetrable, spherical shell."
     "Of course, this was marvellous news and Cavor was out of bed in no time, scattering nurses in all directions. He had no idea what had happened, but it was a lot more exciting than the humdrum piece of nuclear engineering that had started the whole business."
     "By now you're probably all wondering what the devil a sphere of force — as you science fiction writers would call it — has to do with antigravity. So I'll jump several days and give you the answers that Cavor and his team discovered only after much hard work and the consumption of many gallons of that potent Australian beer."
     "The reactor when it had been energised, had somehow produced an antigravity field. All the matter inside a twenty-foot-radius sphere had been made weightless, and the enormous amount of energy needed to do this had been extracted, in some utterly mysterious manner, from the uranium in the pile. Calculations showed that the amount of energy in the reactor was just sufficient to do the job. Presumably the sphere of force would have been larger still if there had been more ergs available in the power source."
     "I can hear someone just waiting to ask a question, so I'll anticipate them. Why didn't this weightless sphere of earth and air float up into space? Well, the earth was held together by its cohesion, anyway, so there was no reason why it should go wandering off. As for the air, that was forced to stay inside the zone of zero gravity for a most surprising and subtle reason which leads me to the crux of this whole peculiar business."
     "Better fasten your seat belts for the next bit: we've got a bumpy passage ahead. Those of you who know something about potential theory won't have any trouble, and I'll do my best to make it as easy as I can for the rest."
     "People who talk glibly about antigravity seldom stop to consider its implication, so let's look at a few fundamentals. As I've already said, weight implies energy — lots of it. That energy is entirely due to Earth's gravity field. If you remove an object's weight, that's precisely equivalent to taking it clear outside Earth's gravity. And any rocket engineer will tell you how much energy that requires."
     Harry turned to me and said: "There's an analogy I'd like to borrow from one of your books, Arthur, that puts across the point I'm trying to make. You know — comparing the fight against Earth's gravity to climbing out of a deep pit."
     "You're welcome," I said. "I pinched it from Doc Richardson, anyway."
     "Oh," replied Harry. "I thought it was too good to be original. Well, here we go. If you hang on to this really very simple idea, you'll be OK. To take an object clear away from the Earth requires as much work as lifting it four thousand miles against the steady drag of normal gravity. Now the matter inside Cavor's zone of force was still on the Earth's surface, but it was weightless. From the energy point of view, therefore, it was outside the Earth's gravity field. It was inaccessible as if it was on top of a four-thousand-mile-high mountain."
     "Cavor could stand outside the antigravity zone and look into it from a point a few inches away. To cross those few inches, he would have to do as much work as if he climbed Everest seven hundred times. It wasn't surprising that the jeep stopped in a hurry. No material object had stopped it, but from the point of view of dynamics it had run smack into a cliff four thousand miles high. . . ."

From What Goes Up by Arthur C. Clarke (1965)

Perry Rhodan Antigravity

I wish to acknowledge the help I received from Michel Van for this section. He wishes to acknowlege the work of the late Rainer Castor, who did a yeoman's work on the scientific aspects of the Perry Rhodan universe. And who was a personal friend of Mr. Van.

In the 1960's Perry Rhodan books, an antigrav is a black box where you feed in power then a miracle occurs! It levitates! Useful for making spacecraft gently lift off, and also handy for antigravity elevators. About Perry Rhodan issue #300, antigrav was developed into a propulsion system. It was more versatile than the old fashion Impuls engine, but it was a power hog. Only smaller spacecrafts could use antigrav propulsion with the relatively weak fusion reactors for power. It wasn't until the 35th century with the advent of the Schwarzschild power reactors that huge spacecraft could use antigrav propulsion.

But in the real world year 2000, author Rainer Castor joined the Perry Rhodan writing team. He invented the details of the system inside the antigrav black box.

The primitive antigravity system is Robert Forward's protational field, which is an excellent choice. Field generators rotate Bose-Einstein condensates to generate the gravitational equivalent of a magnetic field. This is used to create a gravitational field for ship propulsion. But the propulsive force is weak and it is a power hog.

The advanced system uses hypercrystals (quartz crystals embedded with five-dimensional particles). The propulsive force is strong. Still a power hog, though.

Finally the Andruckabsorber ("pressure absorber") or Inertial Compensator was invented. It reduces the inertia of the ship and crew, which means the same propulsive thrust will give the ship a much higher acceleration. It reduces inertia by pushing part of the ship's atoms into hyperspace. There is a limit to how much you can push into hyperspace before the ship gets sucked in entirely, makes a random hyperspace jump to a random location, and shreds your andruckabsorber.

As a side note, the FTL drive in E. E. "Doc" Smith's classic Lensman series is the inertialess drive.

Perry Rhodan antigravity is based on manipulating gravitons. The study of graviton manipulation will lead physicist to the development of faster-than-light hyperspace propulsion.

Perry Rhodan Antigravtriebwerk units have three modes:

  • Gravo neutralizer / Gravo damper: reduces an existing gravitational field
  • Gravo amplifier / Gravitator: amplifies an exsisting gravitational field
  • Repulsor: produces an artificial repulsive force, anti-gravity, a synthetic gravity field of opposite polarity to natural fields

Gravo neutralizers and amplifiers are used to generate artifical gravity inside a spacecraft's habitat module, and to adjust planetary gravity to a comfortable level. Neutralizers are also used along with engines for vehicles (from personal backpack flying units to large cargo aircraft). Amplifiers are also used for attractor beams and for prison bondage fields.

Repulsors are used as defensive armor and as repellor rays.

However their main use is as a reactionless propulsion system: "gravo-lift". Dense objects called "effective masses" are acted upon by the repulsors. These objects are anchored to the main thrust-bearing structural members of the aircraft or starship. When the repulsors push the effective mass in the desired direction, thrust is created on the ship's structure. Yes, this violates Newton's Third Law, but this is a relatively mild violation compared to other equipment in the Perry Rhodan universe.

From my attempts to comprehend the Google Translate version of the German language Perry Rhodan wiki entry, I get the impression that the repulsor units can move their associated effective masses in any direction. Repulsors are not limited to repelling the effective mass directly away.

Ironwolf Antigravity Wood

Ironwolf was a sadly short-lived comic book title by Howard Chaykin. The protagonist: Lord Ironwolf, is the ruler over a planet covered with valuable antigravity wood. Starships are constructed out of the stuff. The evil Empress wants to offer large quantities of the wood as a bribe to the outer barbarians. Ironwolf refuses, is outlawed, and becomes a rebel in his flagship, the Limerick Rake. In order to prevent the wood from falling into the barbarian's hands, he is forced to fusion bomb his own planet to destroy the forests in a firestorm.

Space: 1889 Liftwood

Space: 1889 is a role-playing game that came out about the same time that K. W. Jeter coined the term "Steampunk".

In 1870 Thomas Edison invents the "ether propeller" which can propel Victorian spaceships via the luminiferous aether. He travels to Mars with Scottish soldier of fortune Jack Armstrong, and discovers that Mars is indeed inhabited. The Great Powers of Germany, France, Russia, Belgium, Great Britain, Italy, Japan and the USA rush to establish colonial empires on various regions of Mercury, Venus and Mars.

Mars is particularly valuable, since it is the soul source of the antigravity Liftwood.

Four-Day Planet Contragravity

In many of H. Beam Piper's novels they use the Abbot Lift-and-Drive aka "contragravity". It is used everywhere, from starships, to aircraft, to armored fighting vehicles, to trucks, to cargo skids, to luggage, to small floating floodlamps.

They apparently require quite a bit of power. However this is not a problem with the widespread availability of tiny radiation-free nuclear power cells, some as small as a AAA battery. They are sheathed in "collapsium", which is condensed matter that will not allow radiation to escape nor allow the batteries to be broken open. Collapsium must be a nice thing to have. But in the real world the closest equivalent is neutronium, which explodes like a supernova if you remove it from the hypergravity of a neutron star.

Murell was interested in everything he saw, in the brief time while we were going down along the docks to where the Javelin was berthed. I knew he'd never actually seen it before, but he must have been studying pictures of it, because from some of the remarks he made, I could tell that he was familiar with it.

Most of the ships had lifted out of the water and were resting on the wide concrete docks, but the Javelin was afloat in the pool, her contragravity on at specific-gravity weight reduction. She was a typical hunter-ship, a hundred feet long by thirty abeam, with a squat conning tower amidships, and turrets for 50-mm guns and launchers for harpoon rockets fore and aft. The only thing open about her was the air-and-water lock under the conning tower. Julio, who was piloting the car, set it down on the top of the aft gun turret. A couple of the crewmen who were on deck grabbed our bags and hurried them inside. We followed, and as soon as Julio lifted away, the lock was sealed.

Immediately, as the contragravity field dropped below the specific gravity of the ship, she began submerging. I got up into the conning tower in time to see the water of the boat pool come up over the armor-glass windows and the outside lights come on. For a few minutes, the Javelin swung slowly and moved forward, feeling her way with fingers of radar out of the pool and down the channel behind the breakwater and under the overhang of the city roof. Then the water line went slowly down across the windows as she surfaced. A moment later she was on full contragravity, and the ship which had been a submarine was now an aircraft.

A hunter-ship looks big on the outside, but there's very little room for the crew. The engines are much bigger than would be needed on an ordinary contragravity craft, because a hunter-ship operates under water as well as in the air.

Finally, however, he quieted down, and the boat swung him around, bringing the tail past our bow, and the ship cut contragravity to specific-gravity level and settled to float on top of the water.

(ed note: from the description, it appears that the contragravity field reduces the influence of gravity on whatever is in the field. Either the submarine is build so it will sink to the bottom of Davy Jone's Locker without an active contragravity field (specific gravity greater than 1.0), or the contragravity can increase the influence of gravity as well as decrease it.)

From FOUR-DAY PLANET by H. Beam Piper (1961)

The Secret of the Ninth Planet

The Secret of the Ninth Planet is an archetypal Winston Science Fiction juvenile novel. Evil aliens are stealing Terra's sunlight and diverting the energy to Pluto. Oh noes! And by an outlandish series of events, the eighteen year old protagonist gets the golden opportunity to accompany a mission in an experimental antigravity spaceship to take the battle to the enemy. I mean ordinarily it would be the height of insanity to take a minor on a deadly combat tour in an untested spacecraft, but gee, the plot just gives them no choice. And what a trip it is! Nothing less than a grand tour of the entire solar system, visiting each planet in turn.

Like I said: archetypal Winston Science Fiction juvenile novel

     "We have in my company's experimental grounds one virtually untested vessel which may be able to make a flight to Mars, or any other planet, in the time allowed. This is the craft we refer to as A-G 17, the seventeenth such experiment, and the first to succeed. It is powered by an entirely new method of flight, the force of anti-gravity."
     Burl hung breathlessly on his next words. "You probably know that work on the scientific negation of gravity has been going on since the early 1950's. It was known shortly after experiments had been conducted on atomic and subatomic particles that grounds had at last been found by means of which a counteraction to gravity might be set up. Early subatomic studies showed that such a force was not only theoretically possible, but that certain subparticles actually displayed such tendencies. On the basis of these first discoveries, work has been going on in the development of negative gravitational drive for at least twenty years. As early as 1956, there were not less than fourteen such projects under way in virtually all the leading aircraft industries of the United States, not to mention the rest of the world. In the last few years, at the direction of the Air Force, these projects have been consolidated, placed under one main roof, and brought to its present status, which is, we believe, the one of final triumph."

     It was still, thought Burl, a large crew for a spaceship. No rocket built to date had ever been able to carry such a load. But by then he had realized that the strict weight limitations imposed by rocket fuels no longer applied to this new method of space flight.

     The A-G 17 loomed suddenly above them, and Burl's first impression was of a glistening metal fountain roaring up from the ground, gathering itself high in the sky, as if to plunge down again in a rain of shining steel.
     The ship was like a huge, gleaming raindrop. It stood two hundred feet high, the wide, rounded, blunt bulk of it high in the air, as if about to fall upward instead of downward. It tapered down to a thin, perfectly streamlined point which touched the ground. It was held uprightly by a great cradle of girders and beams. At various points the polished steel was broken by indentations or inset round dots that were thick portholes or indications of entry ports. Around its equator, girding the widest section was a ring of portholes, and there were scattered rings of similar portholes below this.
     As the three men drew near the tail, the great bulk loomed overhead, and Burl felt as if its weight were bearing down on him as they walked beneath.

     Suiting action to the word, the three went over to one of the loading platforms, climbed on the wiry little elevator, and were hoisted up fifty feet to the port in the side of the ship. They entered well below the vast, overhanging equatorial bulge which marked the wide end of the teardrop-shaped vessel.
     They walked through a narrow plastic-walled passage, broken in several places by tight, round doors bearing storage vault numbers. At the end of the passage they came to a double-walled metal air lock. They stepped through and found themselves in what was evidently the living quarters of the spaceship.
     The Magellan was an entirely revolutionary design as far as space vehicles were concerned. Its odd shape was no mere whimsy, but a practical model. If a better design were to be invented, it would only come out of the practical experience of this first great flight.
     It had long been known, ever since Einstein's early equations, that there was a kinship between electricity, magnetism, and gravitation. In electricity and magnetism there were both negative and positive fields manifesting themselves in the form of attraction and repulsion. These opposing characteristics were the basis for man's mastery of electrical machinery.
     But for gravitation, there had seemed at first no means of manipulating it. As it was to develop, this was due to two factors. First, the Earth itself possessed a gravitational phenomenon in this force outside of that intense, all-pervading field. Second, to overcome this primal force required the application of energy on such scales as could not be found outside of the mastery of nuclear energy.
     There was a simple parallel, Burl had been told the day before by Sam Oberfield, in the history of aviation. A practical, propeller-driven flying machine could not be constructed until a motor had been invented that was compact, light and powerful enough to operate it. So all efforts to make such machines prior to the development of the internal combustion engine in the first days of the twentieth century were doomed to failure. Likewise, in this new instance, a machine to utilize gravitation could not be built until a source of power was developed having the capacity to run it. Such power was found only in the successful harnessing of the hydrogen disintegration explosion — the H-bomb force. The first success at channeling this nuclear power in a nonbomb device had been accomplished in England in 1958. The Zeta-ring generator had been perfected in the next decade.
     Only this source of harnessed atomic power could supply the force necessary to drive an A-G ship.
     The nose of the Magellan housed an H-power stellar generator. Within the bulk of the top third of the ship was this massive power source, its atomic components, its uranium-hydrogen fuel, and the beam that channeled the gravitational drive.

(ed note: in fewer words, it's a fusion power reactor)

     "Negating gravity is not a simple matter like inventing a magic sheet of metal that cuts off the pull of the Earth, such as H. G. Wells wrote about," Oberfield had explained. "That is impossible because it ignores all the other laws of nature; it forgets the power of inertia, it denies the facts of mass and density. It takes just as much energy to lift an anti-gravity ship as to lift a rocketship. The difference is only in the practicality of the power source. A rocketship must burn its fuel by chemical explosion in order to push its cargo load upward. Its fuel is limited by its own weight and by the awkwardness of its handling. This A-G ship also must supply energy, foot-pound for foot-pound, for every foot it raises the vehicle. But due to the amount of energy supplied by this new generator, such power is at last available in one compact form in such concentration that this ship could propel itself for hundreds of years."
     He went on to explain that what then happened was that the vessel, exerting a tremendous counter-gravitational force, literally pushed itself up against Earth's drive. At the same time, this force could be used to intensify the gravitational pull of some other celestial body. The vessel would begin to fall toward that other body, and be repelled from the first body, Earth in this case.
     As every star, planet, and satellite in the universe was exerting a pull on every other one, the anti-gravity spaceship literally reached out, grasped hold of the desired gravitational "rope" hanging down from the sky, and pulled itself up it. It would seem to fall upward into the sky. It could increase or decrease the effect of its fall. It could fall free toward some other world, or it could force an acceleration in its fall by adding repulsion from the world it was leaving.
     In flight, therefore, the wide nose was the front. It would fall through space, pulled by the power beam generated from this front. The rear of the spaceship was the tapering, small end.
     As Burl was shown over the living quarters it became plain to him that the actual living spaces in the Magellan were inside a metal sphere hanging on gymbals below the equatorial bulge that housed the power drive. The bulk of this sphere was always well within the outer walls of the teardrop, and thus protected from radiation. Being suspended on gymbals, the sphere would rotate so that the floor of the living quarters was always downward to wherever the greatest pull of gravity might happen to be.
     Burl and the others explored the three floors that divided the inner sphere, all oriented toward Earth. The central floor, housing the sleeping quarters and living quarters, was compact but roomier than might have been expected. There were five bunkrooms, each shared by two men. There was a main living and dining room. On the lowermost floor was the cookroom, a small dispensary, and immediate supplies. On the upper floor was the control room, with its charts and television viewplates which allowed visi n all directions from sending plates fixed on the surface in various areas.
     In the spaces between the inner sphere and the outer shell were the basic storage areas. Here supplies and equipment were being stocked against all possible emergencies. In the tapering space of the tail below the sphere was a rocket-launching tube. Stored in the outer shells were various vehicles for planetary exploration.

     The great generators were beginning to push against Earth's gravity and, as their force moved upward to match Earth's, the weight of everything in their sway decreased accordingly. Lockhart's first move was simply that to reduce the pull of Earth to zero.
     In a few moments that point was accomplished. A state of weightlessness was obtained within the Magellan. Those watching outside from bunkers in the surrounding mountains saw the huge teardrop shiver and begin to rise slowly above its cradle of girders. It floated gently upward, moving slowly off as the force of Earth's centrifugal drive began to manifest itself against the metal bubble's great mass.
     Everyone on the crew had experienced zero gravity, either in the same tests Burl had undergone or on actual satellite flights, and thus far, no one was too uncomfortable. The entire structure of the ship quivered, and Burl realized that the inner sphere which housed their air space was hanging free on its gymbals.
     Lockhart rang a second gong, then turned a new control. The pitch of the generators, faintly audible to them, changed, took on a new keening. The ship seemed suddenly to jump as if something had grasped it. The feeling of weightlessness vanished momentarily, then there was a moment of dizziness and a sudden sensation of being upside down.
     For a shocking instant, Burl felt himself hanging head downward from a floor which had surprisingly turned into a ceiling. He opened his mouth to shout, for he thought he was about to plunge onto the hard metal of the ceiling which now hung below him so precipitously.
     Then there was a whirling sensation, a sideways twisting that swung him about against the straps. As it came, the room seemed to shift. The curved base of the control room, which had been so suddenly a floor, became in a moment a wall, lopsided and eerie. Then it shifted again. and, startlingly, Burl sagged back into his cushioned seat as the hemispherical room again resumed its normal aspect.

From The Secret of the Ninth Planet by Donald Wollheim (1959)

Larry Niven Gravity Drag


Her full name was Slower Than Infinity. She had been built into a General Products No. 2 hull, a three-hundred-foot spindle with a wasp-waist constriction near the tail. I was relieved. I had been afraid Elephant might own a flashy, vulnerable dude’s yacht. The two-man control room looked pretty small for a lifesystem until I noticed the bubble extension folded into the nose. The rest of the hull held a one-gee fusion drive and fuel tank, a hyperspace motor, a gravity drag, and belly-landing gear, all clearly visible through the hull, which had been left transparent.

By then we were close enough to use the gravity drag to slow us. The beautiful thing about a gravity drag is that it uses very little power. It converts a ship’s momentum relative to the nearest powerful mass into heat, and all you have to do is get rid of the heat. Since the ST8’s hull would pass only various ranges of radiation corresponding to what the puppeteers’ varied customers considered visible light, the shipbuilders had run a great big radiator fin out from the gravity drag. It glowed dull red behind us. And the fusion drive was off. There was no white fusion flame to hurt visibility.

The red glow of the radiator fin became more pronounced. So did the dull uniformity of the planetary surface. The planet was a disk now beyond the front window; if you watched it for a while you could see it grow. Turning ship to face the planet had made no difference to the gravity drag.

We came out of hyperspace near the two Sirius suns. But that wasn’t the end of it, because we still faced a universe squashed by relativity. It took us almost two weeks to brake ourselves. The gravity drag’s radiator fin glowed orange-white for most of that time. I have no idea how many times we circled around through hyperspace for another run through the system.

(ed note: the ship had been boosted to relativistic velocity when they paid some technologically advanced aliens to do it. But after the mission they have to slow down via gravity drag.)

From FLATLANDER by Larry Niven (1967)

With Lloobee missing and with the hyperwave smashed, the Argos proceeded to Gummidgy at normal speed. Normal speed was top speed; there are few good reasons to dawdle in space. It took us six hours in hyperdrive to reach the edge of CY Aquarii’s gravity well. From there we had to proceed on reaction drive and gravity drag.

“We could find the ship that brought him down. You can’t hide a spaceship landing. The gravity drag makes waves on a spaceport indicator.”

That was at five-gee acceleration, fusion drive and gravity drag, with four gees compensated by the internal gee field.

And I watched the Drunkard’s Walk, its fusion drive off, floating down ahead of me on its gravity drag.

From GRENDEL by Larry Niven (1968)

Space Anchor

A "space anchor" is a handwaving gizmo that allows a ship to fix its location to a particular point in a gravity field. Which probably counts as a preferred frame. Which is forbidden under relativity. Which means if an author uses such a device they can expect the shade of Albert Einstein to rise up and give you such a pinch.


      WHEN Marty first saw the thing it was nearly dead ahead, half a million miles away, a tiny green blip that repeated itself every five seconds on the screen of his distant search radar. He was four billion miles from Sol and heading out, working his way slowly through a small swarm of rock chunks that swung in a slow sun-orbit out here beyond Pluto, looking for valuable minerals in a concentration that would make mining profitable.
     The thing on his radar screen looked quite small and therefore not too promising. But, as it was almost in his path, no great effort would be required to investigate. For all he knew, it might be solid germanium. And nothing better was in sight at the moment.

     TEN hours later he examined his new find much more closely, with a rapidly focusing alertness that balanced between an explorer’s caution and a prospector’s elation at a possibly huge strike.
     The incredible shape of X, becoming apparent as the Clem drew within a few hundred miles, was what had Marty on the edge of his chair. It was a needle thirty miles long, as near as his radar could measure, and about a hundred yards thick—dimensions that matched exactly nothing Marty could expect to find anywhere in space.
     It was obviously no random chunk of rock. And it was no spaceship that he had ever seen or heard of. One end of it pointed in the direction of Sol, causing him to suggest to Laura the idea of a miniature comet, complete with tail. She took him seriously at first, then remembered some facts about comets and swatted him playfully. “Oh, you!” she said.
     It took a minute to set the autopilot so that any sudden move by X would trigger alarms and such evasive tactics as Clem could manage. He then set a robot librarian to searching his microfilm files for any reference to a spaceship having X’s incredible dimensions.
     Marty brought Clem to a stop relative to X, and noticed that his velocity relative to Sol now also hung at zero. “I wonder,” he muttered. “Space anchor…?”
     The space anchor had been in use for thousands of years. It was a device that enabled a ship to fasten itself to a particular point in the gravitational field of a massive body such as a sun. If X was anchored, it did not prove that there was still life aboard her; once “dropped,” an anchor could hold as long as a hull could last.
     “If it’s human, you mean? No. I know there hasn’t been any ship remotely like that used in recent years. Way, way back the Old Empire built some that were even bigger, but none I ever heard of with this crazy shape …”
     The robot librarian indicated that it had drawn a blank. “See?” said Marty. “And I’ve even got most of the ancient types in there.”
     He paused, frowned at the image of X. “That damned shape — it’s just not right for anything.”

     They had moved Clem to within a few miles of X. Marty mounted his spacebike and approached it slowly, from the side.
     The tiny FM radar on his bike showed him within three hundred yards of X. He killed his forward speed with a gentle application of retrojets and turned on a spotlight. Bright metal gleamed smoothly back at him as he swung the beam from side to side. Then he stopped it where a dark concavity showed up.
     “Lifeboat berth … empty,” he said aloud, looking through the bike’s little telescope.
     At ten yards distance he killed speed again, set the bike on automatic stay-clear, made sure a line from it was fast to his belt and launched himself out of the saddle gently, headfirst toward X.
     The armored hands of his suit touched down first, easily and expertly. In a moment he was standing upright on the hull, held in place by magnetic boots. He looked around. He detected no response to his arrival. Marty turned toward Sol, sighting down the miles of dark cylinder that seemingly dwindled to a point in the starry distance, like a road on which a man might travel home toward a tiny sun.
     Near at hand the hull was smooth, looking like that of any ordinary spaceship. In the direction away from Sol, quite distant, he could vaguely see some sort of projections at right angles to the hull. He mounted his bike again and set off in that direction. When he neared the nearest projection, a mile down the hull, he saw it to be a sort of enormous clamp that encircled X — or rather, part of a clamp. It ended a few yards from the hull, in rounded globs of metal that had once been molten but were now too cold to affect the thermometer Marty held against them. His radiation counter showed nothing above the normal background.
     “Ah,” said Marty after a moment, looking at the half-clamp.
     “I think I’ve got it figured out. Not quite as weird as we thought. Let me check for one thing more.” He steered the bike slowly around the circumference of X.
     A third of the way around he came upon what looked like a shallow trench, about five feet wide and a foot deep, with a bottom that shone cloudy gray in his lights. It ran lengthwise on X as far as he could see in either direction.
     A door-sized opening was cut in the clamp above the trench. Marty nodded and smiled to himself, and gunned the bike around in an accelerating curve that aimed at the Clementine.

     IT’S not a spaceship at all, only a part of one,” he told Laura a little later, digging in the microfilm film with his own hands, with the air of a man who knew what he was looking for. “That’s why the librarian didn’t turn it up. Now I remember reading about them. It’s part of an Old Empire job of about two thousand years ago. They used a somewhat different drive than we do, one that made one enormous ship more economical to run than several normal sized ones. They made these ships ready for a voyage by fastening together a number of long narrow sections side by side, how many depending on how much cargo they had to move. What we’ve found is obviously one of those sections.”
     Laura wrinkled her forehead. “It must have been a terrible job, putting those sections together and separating them, even in free space.”
     “They used space anchors. That trench I mentioned? It has a forcefield bottom, so an anchor could be sunk through it; then the whole section could be slid straight forward or back, in or out of the bunch … here, 'I’ve got it, I think. Put this strip in the viewer.”
     One picture, a photograph, showed what appeared to be one end of a bundle of long needles, in a glaring light, against a background of stars that looked unreal. The legend beneath gave a scanty description of the ship in flowing Old Empire script. Other pictures showed sections of the ship in some detail.
     “This must be it, all right,” said Marty thoughtfully. “Funny looking old tub.”
     “I wonder what happened to wreck her.”
     “Drives sometimes exploded in those days, that could have done it. And this one section got anchored to Sol somehow — it’s funny.”
     “How long ago did it happen, do you suppose?” asked Laura. She had her arms folded as if she were a little cold, though it was not cold in the Clementine.
     “Must be around two thousand years or more. These ships haven’t been used for about that long.” He picked up a stylus. “I better go over there with a big bag of tools tomorrow and take a look inside.” He noted down a few things he thought he might need.
     “Historians would probably pay a good price for the whole thing, untouched,” she suggested, watching him draw doodles.
     “That’s a thought. But maybe there’s something really valuable aboard — though I won’t be able to give it anything like a thorough search, of course. The thing is anchored, remember. I’ll probably have to break in anyway to release that.
     She pointed to one of the diagrams. “Look, a section thirty miles long must be one of the passenger compartments. And according to this plan, it would have no drive at all of its own. We’ll have to tow it.”

     THE next “morning” found Marty loading extra tools, gadgets and explosives on his bike. The trip to X (he still thought of it that way) was uneventful. This time he landed about a third of the way from one end, where he expected to find a handy airlock and have a choice of directions to explore when he got inside. He hoped to get the airlock open without letting out whatever atmosphere or gas was present in any of the main compartments, as a sudden drop in pressure might damage something in the unknown cargo.
     He found a likely-looking spot for entry where the plans had led him to expect one. It was a small auxiliary airlock, only a few feet from the space-anchor channel. The forcefield bottom of that channel was, he knew, useless as a possible doorway. Though anchors could be raised and lowered through it, they remained partly imbedded in it at all times. Starting a new hole from scratch would cause the decompression he was trying to avoid, and possibly a dangerous explosion as well.
     Marty began his attack on the airlock door cautiously, working with electronic “sounding” gear for a few minutes, trying to tell if the inner door was closed as well. He had about decided that it was when something made him look up. He raised his head and sighted down the dark length of X toward Sol.
     Something was moving toward him along the hull.
     He was up in the bike saddle with his hand on a blaster before he realized what it was — that moving blur that distorted the stars seen through it, like heat waves in air. Without doubt, it was a space anchor. And it moved along the channel.
     Marty rode the bike out a few yards and nudged it along slowly, following the anchor. It moved at about the pace of a fast walk. Moved … but it was sunk into space.
     “Laura,” he called, “something odd here. Doppler this hull for me and see if it’s moving.”
     Laura acknowledged in one businesslike word. Good girl, he thought, I won’t have to worry about you. He coasted along the hull on the bike, staying even with the apparent movement of the anchor.
     Laura’s voice came: “It is moving now, towards Sol. About six miles per. hour. Maybe less — it’s hard to read, so slow.”
     “Good, that’s what I thought.” He hoped he sounded reassuring. He pondered the situation. It was the hull moving then, the forcefield channel sliding by the fixed anchor.
     About four hours later the incomprehensible anchor neared the end of its track, within thirty yards of what seemed to be X’s stern. It slowed down and came to a gradual stop a few yards from the end of the track. For a minute nothing else happened. Marty reported the facts to Laura. He sat straight in the bike saddle, regarding the universe, which offered him no enlightenment.
     In the space between the anchor and the end of the track, a second patterned shimmer appeared. It must necessarily have been let “down” into space from inside X. Marty felt a creeping chill. After a little while the first anchor vanished, withdrawn through the forcefield into the hull.

     LAURA and Marty took turns sleeping and watching, that night aboard the Clementine. About noon the next day Laura was at the telescope when anchor number one reappeared, now at the “prow” of X. After a few moments the one at the stern vanished.
     “Must be some kind of mechanism in her still operating.” He went to the telescope and watched number one anchor begin its apparent slow journey sternward once again. “I don’t know. I’ve got to settle this.”
     The doppler showed X was again creeping toward Sol at about six miles an hour.
     “Does it seem likely there’d be power left after two thousand years to operate such a mechanism?” Laura asked.
     “I think so. Each passenger section had a hydrogen power lamp.” He dug out the microfilm again. “Yeah, a small fusion lamp for electricity to light and heat the section, and run the emergency equipment for …” His voice trailed off, then continued in a dazed tone: “For recycling food and water.”
     “Marty, what is it?” He stood up, staring at the plan. “And the only radios were in the lifeboats, and the lifeboats are gone. I wonder … sure. The explosion could have torn them apart, blown them away so…"
     “What are you talking about?”
     He looked again at their communicator. “A transmitter that can get through the noise between here and Pluto wouldn’t be easy to jury-rig, even now. In the Old Empire days …”
     “Now about air —” He seemed to wake up with a start, looked at her sheepishly. “Just an idea hit me.” He grinned. “I’m making another trip.”

     Another door led him into a narrow passage where a few overhead lights burned dimly. Trying to watch over his shoulder and ahead at the same time, he followed the hall to a winding stair and began to climb, moving with all the silence possible in a spacesuit.
     A man came out of a doorway across the corridor, a deck below Marty.
     Marty pulled back two slow steps from the railing, to where he stood mostly in shadow. Turning his head to follow the old man’s gaze, he noticed that the forcefield where the anchors traveled was visible running in a sunken strip down the center of the corridor. When the interstellar ship of which X was once a part had been in normal use, the strip might have been covered with a moving walkway of some kind.
     Sweating in spite of his suit’s coolers, he listened to the singing grow rapidly louder in his helmet. Male and female voices rose and fell in an intricate melody, sometimes blending, sometimes chanting separate parts. The language was unknown to him.
     Suddenly the people were in sight, first only as a faint dot of color in the distance. As they drew nearer he could see that they walked in a long neat column eight abreast, four on each side of the central strip of forcefield. Men and women, apparently teamed according to no fixed rule of age or sex or size — except that he saw no oldsters or young children.
     The people sang and leaned forward as they walked, pulling their weight on heavy ropes that were intricately decorated, like their clothing and that of the old man who had now stepped out of his doorway again to greet them.
     All at once the walkers were very near; hundreds of people pulling on ropes that led to a multiple whiffletree made of twisted metal pipe, that rode over the central trench. The whiffletree and the space anchor to which it. was fastened were pulled past Marty — or rather the spot from which he watched was carried past the fixed anchor by the slow, human-powered thrust of X toward Sol.

     “People,” he said, sitting down. “Alive over there. Earth people. Humans.”
     “You’re all right?”
     “Sure. It’s just—” He told her about it briefly. “They must be descended from the survivors of the accident, whatever it was. Physically there’s no reason why they couldn’t live when you come to think of it — even reproduce up to a limited number. Plants for oxygen — I bet their air’s as good as ours. Recycling equipment for food and water, and the hydrogen power lamp still working to run it, and to give them light and gravity … they have about everything they need. Everything but a space-drive.”
     “All those years,” Laura whispered. “All that time.”
     “Do you realize what they’re doing?” he asked softly. “They’re not just surviving, turned inward on weaving and designing and music.
     “In a few hours they’re going to get up and start another day’s work. They’re going to pull anchor number one back to the front of their ship and lower it. That’s their morning job. Then someone left in the rear will raise anchor number two. Then the main group will start pulling against number one, as I saw them doing a little while ago, and their ship will begin to move toward Sol. Every day they go through this they move about thirty miles closer to home.
     “Honey, these people are walking home and pulling their ship with them.

     MARTY — how long would it take them?”
     “Space is big,” he said in a flat voice, as if quoting something he had been required to memorize.
     After a few moments he continued. “I said just moving a little faster won’t help them. Let’s say they’ve traveled thirty miles a day for two thousand years. That’s — somewhere near twenty- two million miles. Almost enough to get from Mars to Earth at their nearest approach. But they’ve got a long way to go to reach the neighborhood of Mars’ orbit. We’re well out beyond Pluto here. Practically speaking, they’re just about where they started from.”
     Laura went to the communicator and began to set it up for the call that would bring the Navy within a few hours.
     For better or worse, the long voyage was almost over.

From THE LONG WAY HOME by Fred Saberhagen (1961)

Lucky Starr Agrav


Lucky said, "You were saying, Lieutenant, we would have to reach our quarters by Agrav. Were you going to explain what that means?"

The lieutenant, who had also been staring fondly at the V-frog, paused to gather his wits before answering. "Yes. It's simple enough. We have artificial gravity fields (paragravity) here on Jupiter Nine as on any asteroid or on any space ship for that matter. They are arranged at each of the main corridors, end to end, so that you can fall the length of them in either direction. It's like dropping straight down a hole on Earth." Lucky nodded. "How fast do you drop?" "Well, that's the point. Ordinarily, gravity pulls constantly and you fall faster and faster…"

"Which is why I ask my question," interposed Lucky dryly.

"But not under Agrav controls. Agrav is really A-grav: no gravity, you see. Agrav can be used to absorb gravitational energy or store it or transfer it. The point is you only fall so fast, you see, and no faster.

With a gravitational field in the other direction, too, you can even slow down. An Agrav corridor with two pseudo-grav fields is very simple and it has been used as a steppingstone to an Agrav ship which works in a single gravitational field. Now Engineers' Quarters, which is where your rooms will be, is only a little over a mile from here and the most direct route is by Corridor A-2. Ready?"

"We will be once you explain how we're to work Agrav."

"That's hardly a problem." Lieutenant Nevsky presented each with a light harness, adjusting them over the shoulders and at the waist, talking rapidly about the controls.

And then he said, "If you'll follow me, gentlemen, the corridor is just a few yards in this direction."

"Look here," Norrich said. He held up one of the round counters he had been holding. "Gravity is a form of energy. An object — such as this piece I'm holding — which is under the influence of a gravitational field but is not allowed to move is said to have potential energy. If I were to release the piece, that potential energy would be converted to motion—or kinetic energy, as it is called. Since it continues under the influence of the gravitational field as it falls, it falls faster and faster and faster." He dropped the counter at this point, and it fell.

"Until, splash," said Bigman. The counter hit the floor and rolled.

Norrich bent as though to retrieve it and then said, "Would you get it for me, Bigman? I'm not sure where it rolled."

Bigman suppressed his disappointment. He picked it up and returned it.

Norrich said, "Now until recently that was the only thing that could be done with potential energy: it could be converted into kinetic energy. Of course the kinetic energy could be used further. For instance, the falling water of Niagara Falls could be used to form electricity, but that's a different thing. In space, gravity results in motion and that ends it.

"Consider the Jovian system of moons. We're at Jupiter Nine, way out. Fifteen million miles out. With respect to Jupiter, we've got a tremendous quantity of potential energy. If we try to travel to Jupiter One, the satellite Io, which is only 285,000 miles from Jupiter, we are in a way, falling all those millions of miles. We pick up tremendous speeds which we must continually counteract by pushing in the opposite direction with a hyperatomic motor. It takes enormous energy. Then, if we miss our mark by a bit, we're in constant danger of continuing to fall, in which case there's only one place to go, and that's Jupiter—and Jupiter is instant death. Then, even if we land safely on lo, there's the problem of getting back to Jupiter Nine, which means lifting ourselves all those millions of miles against Jupiter's gravity. The amount of energy required to maneuver among Jupiter's moons is just prohibitive."

"And Agrav?" asked Bigman.

"Ah! Now that's a different thing. Once you use an Agrav converter, potential energy can be converted into forms of energy other than kinetic energy. In the Agrav corridor, for instance, the force of gravity in one direction is used to charge the gravitational field in the other direction as you fall. People falling in one direction provide the energy for people falling in the other. By bleeding off the energy that way, you yourself, while falling, need never speed up. You can fall at any velocity less than the natural falling velocity. You see?"

Bigman wasn't quite sure he did but he said, "Go on."

"In space it's different. There's no second gravitational field to shift the energy to. Instead, it is converted to hyperatomic field energy and stored so. By doing this, a space ship can drop from Jupiter Nine to Io at any speed less than the natural falling speed without having to use any energy to decelerate. Virtually no energy is expended except in the final adjustment to Io's orbital speed. And safety is complete, since the ship is always under perfect control. Jupiter's gravity could be completely blanketed, if necessary.

"Going back to Jupiter Nine still requires energy. There is no getting around that. But now you can use the energy you had previously stored in the hyperatomic field condenser to get you back. The energy of Jupiter's own gravitational field is used to kick you back."

The first Agrav ship ever to be built was named Jovian Moon and it was not like any ship Lucky had ever seen. It was large enough to be a luxury liner of space, but the crew and passenger quarters were abnormally crowded forward, since nine tenths of the ship's volume consisted of the Agrav converter and the hyperatomic force-field condensers. From the midsection, curved vanes, ridged into a vague resemblance to bat's wings, extended on either side. Five to one side, five to the other, ten in all.

Lucky had been told that these vanes, in cutting the lines of force of the gravitational field, converted the gravity into hyperatomic energy. It was as prosaic as that, and yet they gave the ship an almost sinister appearance.


Grav Constrained Matter

This is really weird stuff. Common matter falls down in a gravity field. Antigravity matter falls up in a gravity field. But gravitationaly constrained matter can neither fall up nor down, it can only move at 90° to the gravity field. Or at least move with great difficulty.

So far I've only found very few examples of this unconventional concept. With the exception of those silly Planar Shockwaves you see in movies like the Special Editions of the original Star Wars trilogy and space-based video games,

CITIES IN FLIGHT by James Blish (1956)
TDX is a high explosive containing gravitationally polarized carbon atoms. They can only move at right angles to the gravity gradient. Useful for cutting down trees with the planar explosion.
Polity Series by Neal Asher (2006)
planar explosives constructed by molecular engineering produce 2D blasts
THE CITY AND THE STARS by Arthur C. Clarke (1956)
The moving sidewalks in the city of Diaspar are composed of matter that is fluid perpendicular to the gravity gradient but solid parallel to the gradient.

      On the whole, however, the plans were simple, and putting them into effect had seemed heavy but relatively uncomplicated labor. Some opposition, of course, had been expected from the local bandit towns.
     But Amalfi had not expected to lose nearly 20 per cent of his crews during the first month after the raid on Fabr-Suithe.

     It was Miramon who brought the news of the latest work camp found slaughtered. Amalfi was sitting under a tree fern on high ground overlooking the city, watching a flight of giant dragonflies and thinking about heat transfer in rock.
     “You are sure they were adequately protected?” Miramon asked cautiously. “Some of our insects—”
     Amalfi thought the insects, and the jungle, almost disturbingly beautiful. The thought of destroying it all occasionally upset him. “Yes, they were,” he said shortly. “We sprayed out the camp areas with dicoumarins and fluorine-substituted residuals. Besides—do any of your insects use explosives?”

     “Explosives! There was dynamite used? I saw no evidence—”
     “No. That’s what bothers me. I don’t like all those felled trees you describe; that sounds more like TDX than dynamite or high explosive. We use TDX ourselves to get a cutting blast—it has the property of exploding in a flat plane.”
     Miramon goggled. “Impossible. An explosion has to expand evenly in all directions that are open to it.”
     “Not if the explosive is a piperazohexynitrate built from polarized carbon atoms. Such atoms can’t move in any direction but at right angles to the gravity radius. That’s what I mean. You people are up to dynamite, but not to TDX.”

From CITIES IN FLIGHT by James Blish (1956)

(ed note: the roadways are sort of a high-tech moving sidewalk)

      His mild annoyance vanished almost at once. There was no reason why Alystra should not come with him if she desired. He was not selfish and did not wish to clutch this new experience to his bosom like a miser. Indeed, he might be able to learn much from her reactions.

     She asked no questions, which was unusual, as the express channel swept them out of the crowded heart of the city. Together they worked their way to the central high-speed section, never bothering to glance at the miracle beneath their feet. An engineer of the ancient world would have gone slowly mad trying to understand how an apparently solid roadway could be fixed at the sides while toward the center it moved at a steadily increasing velocity. But to Alvin and Alystra, it seemed perfectly natural that types of matter should exist that had the properties of solids in one direction and of liquids in another.

     As Alvin and Alystra moved outward from the city’s heart, the number of people they saw in the streets slowly decreased, and there was no one in sight when they were brought to a smooth halt against a long platform of brightly colored marble. They stepped across the frozen whirlpool of matter where the substance of the moving way flowed back to its origin, and faced a wall pierced with brightly lighted tunnels. Alvin selected one without hesitation and stepped into it, with Alystra close behind. The peristaltic field seized them at once and propelled them forward as they lay back luxuriously, watching their surroundings.

From THE CITY AND THE STARS by Arthur C. Clarke (1956)



     Tesla and Edison had the War of the Currents. There was the struggle over gaslights vs. electric bulbs. Then there was VHS vs. Betamax (for those of you old enough to remember videotaping). Mac and Microsoft still aren't talking. Wherever there's a way to build an invention there's likely to be several. But then at Low Stellar and Late Solar levels of technology you get the Gravity Wars!

     Gravity control in most settings makes space so much easier (meaning you can get to it and get killed quicker and cheaper.) Instead of using a honking huge rocket to reach orbit you can use a consumer friendly launch with a reasonable payload to fuel ratio. You just throw a switch and some of the Earth's (or other planet's) gravity is negated. Doing a space time sidestep you find yourself in orbit.

     This is going to piss off many powerful and wealthy people.

     Think about it. You're running a surface to orbit transport company and have invested in a laser launch system or space tower or even just a reusable rocket and launch pad. That's $$$$! Then along comes Pop Jenkins who builds an anti-grav car in his garage for GHU's sake! the cost of getting to orbit becomes the price of some current (pennies unless you're buying it in New York City). What would your reaction be? What would the headlines read?

     Local Inventor Dies in Garage Fire! Plucky Nephew and Brainy Neighbor Girl Feared Dead as Well! Page 2

     Maybe I'm being a little cynical. Maybe Pop Jenkins announces his discovery from orbit in his Solar Winnebago. The secret is out. What the hell do you do with your infrastructure? All those rockets and launch platforms are junk and all your revenue will dry up.

     Even worse, anti-gravity negates many reasons for going into space. A popular form form of MacGuffinite is microgravity manufacture. Now you can have microgravity or true zero gravity anywhere. So why even go to space?

     Wait! Your company has some long term contracts? Smart. Even if transport to orbit costs go from $10,000 a kilo to $0.25 you have contracts! Tough s**t! Build an anti-grav transport with a loan or your savings. Use the increased profit from using it to retire your rocket fleet and build more anti-grav transports. Meanwhile delay the anti-grav revolution as much as you can!

     Legislation- You need to carefully monitor and license this new tech. Why you could drive a shuttle up to light speed and have it smack into a planet!

     Economics- If you need Element X to produce anti-grav then Element X becomes very expensive. Or in a rift on legislature processing and acquiring Element X requires special licenses.

     Health Concerns- the long term effects of artificial gravity on the human body are unknown! This needs further study!

     National Security- This new technology can threaten the nation and must be restricted to the military. This might even be a fair cop. Those planet smashing gigs are pretty scary.

     Slander! Anti-gravity is weakening the Earth's gravitational field/causing global warming/immorality and pulling meteors at your ship. Besides a little coriolis force never hurt anyone and keeps the coaster manufacturers in business. Those people have kids!

     More than likely the new tech will have drawbacks and limits. If it's very short ranged it might only be used to provide gravity on space stations and low gravity worlds to keep settlers from becoming anorexic beanpoles. Those beautiful rotating space stations and passenger sections are all suddenly out of fashion though.

     Perhaps anti-gravity is a  repulsive force instead of a shield or nullification. In that case it works when you have a planet or other massive body. The chemical rocket guys are out of business. The ion rocket cartel is still going strong for deep space missions. Just to further ruin Doc Jenkins' day, getting to orbit and being in an orbit are two different things. If anti-gravity lifts you a couple hundred klicks you are just hovering. Shut off the anti-grav and you fall. Worse, there are things moving in orbit that can hit you like little bits of dynamite. So an anti-grav might reduce the fuel and thrust needed to get to orbit but not negate it but Big Rocket stays in business.

     It does feel a little immoral though. Like you build a fusion reactor that uses hydrocarbons as fuel so Big Oil (boo!) stays in business or a super rocket fueled by tobacco.

From THE GRAVITY WARS by Rob Garitta (2016)


"Para" means "at or to one side of, beside, side by side". The idea is that "paragravity" means "ersatz-gravity" or "synthetic gravity". What we want to do is somehow generate 1 Terran gravity without the need of using 1 Terran mass (i.e., a sphere that weighs 5,972,000,000,000,000,000,000 metric tons). Preferably by something you can turn on and off with the flick of a switch, and that can be adjusted over a range of gravitational values.

Yes, the Starship Enterprise can have 1 gee of gravity inside if it carries on its belly a planet or black hole that has the same mass as Terra, but this ain't practical. For one thing it means the Enterprise's impulse drive would have to be capable of accelerating Planet Terra itself to the second star on the right straight on until morning if it had a sufficiently strong tow cable. We want to somehow generate 1 gee of synthetic gravity with something as lightweight as floor decking.

The standard use for paragravity is to provide artificial gravity for crews in spacecraft without the need for cantankerous centrifuges. Artificial gravity is important, due to the severe health risks of free fall.

But if you use paragravity to lay the ship's decks at ninety degrees to the thrust axis like a passenger airplane, RocketCat will kick you in the gonads.

Paragravity can also be used for acceleration compensation, i.e., preventing rocket thrust from turning the crew into a thin layer of chunky salsa on the decks. The acceleration limit for astronauts is about 30 gees for no longer than ten minutes. And that is pushing it. However if the spacecraft is accelerating at 100 gees but the paragravity is pulling the astronauts upwards at 99 gees, the astronauts will experience a net force of only one gee downward. Just like on Terra.

Or a paragravity drive that acts on all the ship and crew atoms equally. So regardless of the acceleration, the crew floats around inside the ship in free fall.

Another use is to use paragravity to create attractor and pressor beams. While they are great for grappling spacecraft and cargo, they can also be adapted into a propulsion system that is almost a reactionless drive. Or a super-efficient mass driver rocket. Or a meteor repellor. Or a defensive repulsor field warding off missiles and other kinetic energy weapons. Or gravitic-confinement fusion power generator. Or super-efficient coilgun. Or super efficient particle beam weapon. Or otherwise weaponized.

Let's face it: paragravity is going to have a thousand and one uses. Just like electromagnetism. Remember when lasers were invented and the only application people could think of was a ray gun? Nowadays they are in everything: from surveying equipment, to laser gyroscopes, to making holograms, to optical tweezers, to scanning the bar-code on your groceries. Paragravity is going to be much like that.

Crib notes for the second paragraph above:

Attractor and Pressor beams
     Narrow beams that can be focused on an object to move them closer or farther. According to physics there is not straightforward way to make these.
     Electromagnets will omnidirectionally attract all ferromagnetic objects in range, not just objects in a narrow beam. They will not repel an object unless it is diamagnetic or magnetic with the like pole facing. Not to mention the lack of stability and the fact that the range is probably measured in meters.
     Lasers used as optical tweezers can attract and repel, but the force is measured in piconewtons and the maximum size of the object is measured in nanometers or micron. Powerful lasers can repel an object by vaporizing part of it to make a crude rocket jet (i.e., an impromtu laser launcher). Neither of which is anything like the tractor beams you see in Star Trek.
     In theory a laser-like coherent beam of gravitational waves could be focused on an object to move them closer. Repelling objects does not seem to be possible, though, unless paragravity allows repulsive gravity.
Gravitic-Confinement Fusion Power Generator
There are currently no practical fusion power designs. The problem is: it is a challenge to confine the equivalent of a miniature exploding thermonuclear warhead. You cannot confine it with chamber walls made of matter because the sun-hot temperatures will instantly vaporize them. Current research is to confine the fusion reaction using walls made of energy. Inertial confinment uses inertia and a battery of laser beams. Magnetic confinement uses powerful magnetic fields. And so far for every design that stops one way that the fusion plasma wriggles out of the confinement, the fusion plasma reveals ten new ways to squirm out. In theory a strong gravity field will do the trick. After all, that's the method used by stars for their fusion reactions.
Super Efficient Particle Beam Weapon
     Particles with a negative charge (electrons) are accelerated using coils with a positive charge (because unlike charges attract). Particles with a positive charge (protons), are accelerated with negatively charged coils for the same reason. Particles with no charge (neutrons) cannot be accelerated with charged coils. Actually charged particles are accelerated with arrays of coils. At any given microsecond the coil immediately in front of a cloud of electrons is negatively charged (to attract) while the coil just behind is positively charged (to repel). As the cloud passes a coil that coil's polarity is reversed.
     Of course targeted ships can defend themselves from charged particle beam weapons by using defensive fields with positive or negative charges. They cannot use such fields to defend against neutral particle beams, but that's not a problem because you cannot make neutron weapons in the first place.
     Ah, but you could accelerate electrons, protons, and neutrons all at once using paragravity. This would allow efficient electron and proton beams, and allow neutron beams to exist at all. The drawback is that ships can defend themselves with repulsive paragravity.

      I have very few soap boxes that I climb up on and one of them is gravity generators or gravplates.
     My main gripe is with gravity plates. Why, when you have perfectly good torchship capable of 1G acceleration, do you need gravity plates?
     What's gravity? Curved space-time. We've done enough experiments and observations to confirm what Einstein said it was. Curved space… and time. We won't worry about time right now.
     And what curves space? Mass, lots of it. The property of "mass" is a manifestation of potential energy transferred to particles when they interact ("couple") with the Higgs field, which had contained that mass in the form of energy. So, by that definition, you need a lot of potential energy to make a lot of mass.

     So let's do the numbers. What is 1G?

g = m / (r / 6380)2


g = gravitational acceleration (earth gravities)
m = mass of the Earth in Earth masses (1, which is 5.972×1024 kg just so you know)
r = radius of the Earth in kilometers (6380 km)

Therefore the equation works out to 1G, which is an acceleration of 9.8 m/s2.

Let's propose that a gravity plate is 1 meter square, and consists of one hundred 10cm×10cm×10cm generator cells (1000 cubic centimeters). So we just need to work out how much energy one cell needs to have mass to generate 1G. Solve for m in the above equation:

m = (g * r2) / 40,704,400

g = 1 gees and r = 0.0001 kilometers (10 cm)

m = (g * r2) / 40,704,400
m = (1 * 0.00012) / 40,704,400
m = 0.00012 / 40,704,400
m = 0.00000001 / 40,704,400
m = 2.45673686×10-16 Earth masses = 1,467,163,252.79 kg

1,467,163,252.79 kg in a 1000 cubic cm generator cell means a density of 1,467,163.25 kg/cm3. This is denser than (electron) degenerate matter (10,000 kg/cm3) but less than neutronium (neutron degenerate matter), (5.5×1012 kg/cm3). This is per cell (100 cells per gravity plate).

The amount of energy needed to create the necessary energy density to simulate that mass (E=mc2) is 1.32044693×1017 joules. That's a bit shy of the total energy from the Sun that strikes the face of the Earth each second. Per cell (1/100th of a gravity plate). And all this assumes 100% efficiency, with no loss anywhere. Even at 1% heat loss, the amount of heat would be 1.3×1012 joules, about equal to the total fuel energy of 48,765L of Jet A-1 fuel, each second.

Now multiply this by the typical square meterage of your average Free Trader. Turn on the gravity and watch your ship shine as bright as a star for a brief moment…

by John Reiher (2017)

Scientifically speaking, the Larten Theory of Gravities was three decades outmoded, but it still served well enough for Navy textbooks. So, as far as Lieutenant-Commander Laurent Zai was concerned, there were four flavors of graviton: hard, easy, wicked, and lovely.

Hard Gravity was also called real gravity, because it could only be created by good old mass, and it was the only species to occur naturally. Thus fell to it the dirty and universal work of organizing solar systems, creating black holes, and making planets sticky.

The opposite of this workhorse was Easy Gravity, unrelated to mass save that easy gravity was hapless against a real gravity well. Hard gravitons ate easy ones for lunch. But in deep space, easy gravity was quite easy to make; only a fraction of a starship's energy was required to fill it with a single, easy gee. Easy gravity had a few problems, though. It was influenced by far-off bodies of mass in unpredictable ways, so even in the best starships the gee-field was riddled with microtides. That made it very hard to spin a coin in easy gee, and pendulum clocks, gyroscopes, and houses of cards were utterly untenable. Some humans found easy gee to be sickening, just as some couldn't stand even the largest ship on the calmest sea.

Wicked Gravity took up little room in the Navy's manuals. It was as cheap as easy gee, and stronger, but couldn't be controlled. It was often called chaotic gravity, its particles known as entropons. In the Rix Incursion, the enemy had used wicked gee as a devastating but short-range starship weapons. Exactly how these weapons worked was unclear—the supporting evidence was really a lack of evidence. Any damage that followed no understood pattern was labeled "wicked."

The Lovely particle was truly queen of the gravitons. Lovely gee was transparent to hard gravity, and thus when the two acted upon matter together it was with the simple arithmetic of vector addition. Lovely gravity was superbly easy to control; a single source could be split by quasi-lensing generators into whirling rivulets of force that pulled and pushed their separate ways like stray eddies of air around a tornado. A carefully programmed lovely generator could make a seemingly strewn pack of playing cards "fall" together into a neat stack. A stronger burst could tear a human to pieces in a second as if some invisible demon had whirled through the room, but leave the organs arranged by increments of mass on a nearby table. Unfortunately, a few million megawatts of power were necessary for any such display. Lovely gee was costly gee. Only Imperial pleasure craft, a few microscopic industrial applications, and the most exotic of military weapons used lovely generation.

From THE RISEN EMPIRE by Scott Westerfeld (2003)

Robert Forward

The late Dr. Robert L. Forward was a real physicist whose life's work was gravity research. He invented the Forward Mass Detector and had 18 patents to his name, including the Statite. He was the science fiction writer's friend, writing fiction himself and producting research on juicy SF projects like time travel, negative matter, antimatter rockets, and interstellar laser sail starships.

This means all of his material is not science fiction. It is real.

His most accessable book on these topics is the collection of science essays Indistinguishable from Magic.

Given his life's work, he does have a few things to say on the topic of gravity.

The main thing he said that stuck in my mind was about creating fields. He said modern technology uses electromagnetic fields everywhere, because they are so easy to create. All you have to do is take powerful electric charges (electrons) and move them near the speed of light along a path (as a current in a wire).

So in order to use gravitic fields, all you have to do is take powerful gravitational charges and move them near the speed of light along a path. Unfortunately "powerful gravitational charges" means white dwarf star material (1×109 kg/m3), neutronium (4×1017 kg/m3), or Primordial black holes (up to 1023 kg each). It takes titanic particle accelerators to move tiny subatomic particles near the speed of light, the mind boggles at what you'd need to accelerate something so dense that a teaspoon full would weigh as much as Mount Everest.

Since this is utterly beyond our current technology, we do not use gravitic fields.


(ed note: This is not science fiction, it is reality)

The Einstein Theory of Gravity is more complex than the two previous theories of gravity. In a simplified form it can be expressed as:

"A mass causes space to curve. Other masses move in that curved space."

In the Einstein view of gravity, mass does not cause gravity. Instead mass curves space and curved space causes gravity. A good analogy is to imagine a rubber sheet stretched over a frame. If you put a heavy ball bearing in the center of the rubber sheet, the weight of the ball would cause a curved depression. The mass of the heavy ball bearing has "curved" the rubber sheet "space". If you then drop a tiny marble on the curved rubber sheet, the marble would immediately start to roll toward the center as if the large ball were attracting it. But there is no direct attraction between the ball bearing and the marble, the ball bearing is curving the rubber sheet and the marble is responding to the curvature of the rubber (and the gravity of the Earth). If the marble were tossed properly into the curved depression in the rubber sheet, it would go into an "orbit" around the heavy ball bearing at the center.

Because the Einstein Theory of Gravity is more complex than the Ug or Newton theories, it can give us more handles by which we can control gravity. There are at least two ways that we can use the Einstein Theory of Gravity to negate the gravity field of the Earth. There are also two ways we can use the Einstein Theory of Gravity to make a mass push instead of pull.

(Method One: Special Relativity: Protational Field)

In the scientific studies of electricity, it has been found that electricity and magnetism are related. If you change or move electricity, you make magnetism, and if you change or move magnetism, you make electricity again. This transformation between electricity and magnetism is used to make your automobile run. The electricity in your car battery is only twelve volts, not strong enough to run your spark plugs. This low voltage electricity is used to create magnetism in the spark coil. The magnetism temporarily stored in the coil is then released very rapidly when the points open. This rapidly changing magnetic field then generates the powerful, high-voltage sparks that are used by the spark plugs. By using the magnetic field as an intermediate step, the automotive engineers have found a way to convert weak electric forces into strong electric forces.

The Einstein Theory of Gravity says that gravity behaves the same way as electricity. If you take a mass and the gravity field that surrounds it, and move the mass very rapidly, you can create a new field, the gravitational equivalent of magnetism. It is not magnetism, but a completely new field (Protational Field). If you can then cause that new field to change, then you can create a stronger gravity field than you started with. More importantly, that stronger gravity field can be made to appear at a place where there is no mass, and can be made either attractive or repulsive.

Conceptually, there are a number of ways that such a gravity machine could be made. One idea is to roll up some hollow pipe to form a long coil, like the curly cord on a telephone. [See Figure 10.] We then bend the long coil around until the two ends meet to form a curly closed ring.

If the pipes are filled with massive liquid and the liquid is moved back and forth in the pipes rapidly enough, then an alternating push-pull gravity field will be generated at the center of the ring. If the machine was big enough, and the liquid was dense enough and moving fast enough, then we would have a gravity catapult that could launch and retrieve space ships by its gravity repulsion and attraction.

How big? How dense? How fast? Unfortunately, the machine has to be as big as the distance over which you want the gravity effects to operate (i.e., the range of the gravity field is about equal to the diameter of the coil). The liquid has to be as dense or denser than white-dwarf-star material (1×109 kg/m3), and the speed of the flow has to be so high that the ultradense liquid will approach the speed of light in a few milliseconds (implying that the energy requirements will be astronomical, and maybe implying that the gravity field can only be generated for a few milliseconds).

I am afraid that it will be some time before we have all that gravitational technology well in hand. But we do have the theory needed to design our gravity catapult, and some time in the long distant future we will have college classes full of bright students taking their first course in Gravitational Engineering, studying the turbulent flow in ultradense matter and producing more and more efficient designs for the gravitational attractor and repulsor beam intensities to minimize passenger discomfort during the launch or retrieval of an interstellar passenger liner.

(Method Two: General Relativity: Frame Dragging)

The Einstein Theory of Gravity can give us yet another way to control gravity. One of the strangest facets of the Einstein Theory of Gravity is the concept of curved space. The method by which a massive object causes a curvature in space is difficult to really comprehend. It is as if the mass had grabbed hold of space and pulled the space into it. This grip of mass on space is still maintained when the mass is moving. The space seems to move along with the mass. This effect, called the "dragging of the space-time coordinate frame", is the basis for another future magic type of antigravity machine.

If you are near a rapidly moving dense mass, you will find yourself "dragged" along in the direction of the moving mass. One could envision a "lift" shaft, lined with pipes full of rapidly flowing ultradense fluid that wafts you rapidly up to the top of a mile-high building. But more likely this "drag" effect will be used in space as a gravity catapult for shipping purposes within the Solar System. This machine would again be in the form of a ring of ultradense matter, but this time the ring would be uniformly whirling from inside-out, like a gigantic smoke-ring.

If a spaceship entered such a toroidal gravity catapult through the hole from one side, it would be expelled out the other side of the hole with a greatly increased velocity. If the spaceship were falling in toward the Sun from the asteroid belt with a high velocity, it would be gently stopped in Earth orbit by threading the torus in the opposite direction. Since the forces on the spaceship during acceleration and deceleration are gravitational forces which act equally on every atom in the ship, all the atoms in the spacecraft are stopped at the same rate and at the same time. So, even though the accelerations and decelerations can be at rates equivalent to hundreds of Earth gravities, the passengers on those spacecraft will not even have to turn in their martini glasses for "landing" in the Earth-Moon system, much less buckle their seatbelts, stow their overhead luggage, raise their seatbacks, and secure their tables.

From INDISTINGUISHABLE FROM MAGIC by Robert Forward (1995)

Le Sage's Repulsive Gravity

Le Sage's 1748 theory of gravitation is based on the non-intuitive idea that gravity is a repulsive, not attractive force. The force can be shielded by matter.

How does this work?

Imagine yourself far from any planet. Your body is bombarded by repulsive gravity from the entire universe around you. Since all the repulsion pushing you to the left is balanced by the repulsion pushing you to the right, the net result in the left-right axis is zero. The same applies in any other axis, so if you were in the depths of space you'd experience zero gravitational acceleration.

Now imagine that Terra is below you. Suddenly the gravitational repulsion of the universe coming from below is diminished by the shielding provided by the matter of Terra. The repulsion coming from above is now stronger than the repulsion from below. The net result is one Terran gravity of acceleration, pushing you in the direction of Terra.

Alas, Le Sage's theory is pretty much discredited nowadays, because it makes predictions that do not occur in the real world.

For one thing, it assume a select frame of reference, that is, the repulsive gravity particles are evenly distributed in all directions. Unfortunately, if the object starts to move in relation to that frame, it will be hit with more gravity particles in head-on collisions than in rear-end collisions. The effect is that everything will move like it is embedded in tar or other thick liquid. Which doesn't happen in the real world.

Recall Not Earth

C.C. MacApp's nearly forgotten and definitely underrated novel Recall Not Earth actually uses Le Sage's Repulsive Gravity theory.

In the novel, scientists invent a "gravity shield" where by adjusting a knob the shield will reduce the repulsion effect from the universe to any desired degree. Starships incorporate an array of gravity shields on their hulls facing in all directions. By turning on the appropriate shield, the starship can instantly accelerate in the appropriate direction.

The best part is since gravitational acceleration affects all atoms equally (starship and crew), the crew does not feel the acceleration. The ship can be accelerating at 100 gees but the crew is still floating around inside. The reason this does not happen with a rocket is because the rocket acceleration affects only the atoms of the rocket engine, which pushes on the thrust frame of the spacecraft, which pushes on the spacecraft's habitat module, which pushes on the bodies of the crew, who get mashed into their acceleration couches.

This technique is kind of in a gray area between antigravity and paragravity, since is uses gravity shields (antigravity) to generate gravity (paragravity). I'm filing it under paragravity because effects are more important than causes. You quickly learn that if you play the Hero System RPG. For instance, in the Hero System, a given "power's" cause can be a laser beam, bullet, spray of burning liquid, hypnotic stigmata, thown rock, poison dart, homing missile, boomerange, arrow, swarm of angry hornets or psychokinetic thrust. But the imporant part is the effect: in this case "energy blast", defined as "inflicting damage on your opponent at range". The cause is more or less window dressing.

So the important part is the effect: generating a gravity field for acceleration. The fact that it is done by using gravity shields in a Le Sage universe is window dressing. So I am filing this under "paragravity".

The Chelki, under the direction of a Full Male who was second in command here on Akiel, had done an excellent job of refitting and conditioning the old Vul ship (and the eight smaller ones as well). The grav drive was tuned so precisely that John could lift the sixty-thousand-ton vessel a half-inch from the concrete floor of the vast grotto where she lay hidden and set her down again in increments of a quarter-inch, all without the slightest jar or sensation of inertia. Such tuning was important; in combat, a ship's computers (to say nothing of her flesh-and-blood pilots) might demand that she halt instantly, from a velocity of an appreciable fraction of light-speed, or dart away just as instantly on a different course. The gravs had to act upon every component (including passengers) at the same exact moment and with the same force, else she'd be torn apart or her passengers squashed by acceleration.

It was peculiar, he mused, how so many species (of humanoids, at least) discovered the gray drive (and related null drive) at about the same point in their technological development, almost as if it were programmed into the course of science.

Mankind had developed the grav drive within a reasonable time after two monumental discoveries: first, that gravity was a push, not a pull; second, that the push could be screened off by a sheet of any of several special alloys under the influence of certain force fields distantly related to electricity.

This is why a push had always been mistaken for a pull: one of the basic facts of the "normal" universe is that all of space — every cubic centimeter of it, from all directions and all distances up to (and perhaps including) whatever "infinity" exists — repels matter. It repels matter ceaselessly, as if trying to squeeze it out of existence.

But, as if there were some conscious community of mutual assistance, each particle of matter shields every other particle against this push by space. That is as if one opaque ball cast a shadow upon another. And, while space shoves against matter from all directions, there is nothing correlated in this shove; no transverse action or other baffling peculiarity, as with the front of a light wave. Each discrete quantum of space aims a determined straight-line punch continuously at every particle, as if no other quantum of space existed. The punches do not get tangled up or canceled out or deflected. They do reinforce each other, but only in an additive straight-line way.

In one thing the old physics was partly correct: the force of a push does vary inversely with distance, but not in. direct ratio or in the ratio of squares or cubes. The ratio, which can be measured with some accuracy by an ingenious experiment (which, incidentally, led to the invention of the mass detector), has something to do with the number of dimensions that exist in "normal" space. And that is not a matter to discuss casually.

So, the situation exists that every particle of matter is being shoved at from every direction, but is shielded to some tiny extent by every other particle. But the mutual shielding of two particles is only along the straight line joining them. Therefore, what can two particles do but move toward each other? Along that one line, the pressure upon them is lessened by a very small fraction.

Naturally, two electrons, for instance, separated by a distance of several thousand light-years, would take a very long time to come together (not even considering that they were not the only two particles in space). But time is long, and space is patient. Hence particles become atoms, and atoms molecules, and molecules solid masses (if one can stomach that latter inexactitude).

There are counterforces that prevent space from squeezing all matter into one inconceivable ball. One such force is inertia ("centrifugal force" in the case of two particles or rocks or stars orbiting each other). A second such force is the natural repulsion between particles having like charges: electron repelling electron; positron repellng positron. Another is the pressure of radiant energy, as in the terrific effort of a hot star to explode. And there are others not describable in such simple terms.

So, when a considerable mass has been pushed together, it has a considerable effect of shielding against space. For instance, a man standing upon a planet is partly shielded from almost one hundred and eighty degrees of space. The other half of space pushes him against the planet. Semi-primitive man, with his reasonable but unreliable tendency to see things as they appear, called this effect "gravity" and thought it was a pull by the planet. Null-age man, with his perhaps not reasonable propensity for the complex (fore­shadowed, maybe, by such utterly improbable developments as the internal-combustion engine), seized upon the true nature of "gravity" and put it to work (as had, long before, various other equally antipractical, venturesome, stubborn species).

All particles of matter act as natural shields against the push of space, but with limited efficiency. Artificial shields can be made that perform, at optimum, with awesome efficiency. Thus, if a person standing on Earth held a shield above his head and activated it, he would be propelled violently into the air by the residual "space push" penetrating the planet and shoving at him from below. So would a cone of soil (though, since the shielding falls off with distance from the shield, and also because of the geometry of the situation, the cone would not be very long).

The residual push penetrating Earth could be, and was, calculated at approximately two hundred and fifteen gees, and from that (assuming various things) it was clear that Earth, in effect, screened off slightly less than one-half of one percent of the push from half of space. Or: maximum theoretical "gravity," anywhere, was two hundred and sixteen gees.

John had never found that theory particularly reassuring. Two hundred gees, or considerably less, could make puree of a man!

(Note: it is possible to build a shield that will stop the push from one direction only. That is desirable in self-propelled missiles, in certain instruments, and in special tools.)

(Further note: due to certain peculiar properties of space and of shields, it is possible to design the latter to produce a "lee" of a particular shape: conical, spreading, parallel beam, and so forth. For instance, the use of high shielding and a long tapering cone, combined with the one-way effect, gives the weapon called the "rupter" — intense "push" is applied to the target or a small zone of it, and when the push is applied and interrupted and reapplied at a suitable rate, the target can be shaken to pieces. Rupters have ranges limited, in practice, to a few miles. Another example of special shields is in arranging "artificial gravity" within a ship. Without artificial gravity, passengers would suffer various discomforts, some fatal.)

Obviously, if you build a shield into or onto a structurally strong container, and activate it, the whole container will be urged, to some degree, in the direction of the shield. If you take a cylindrical tank of, say, one thousand gallons capacity, put an airtight hatch in it, and fit a shield flat upon one end, you have the fundamentals of a spaceship. Such a ship, if the shield is designed for variable and closely controlled input of power, can rise slowly and gently from a planet's surface without pulling a divot of the planet with it.

Commonly, ships are cylinders of high-strength steel, less than twice as long as their diameters, with shields at either end (occupying the full cross section as nearly as possible) and smaller auxiliary plates at various points of the cylindrical walls (arid sometimes others distributed along cross sections between the two ends). Application of power to any shield or combination of shields is controlled by a special computer, which is usually in turn controlled by the main computer, since manual control might be jerky and dangerous. A ship in space can. achieve startling acceleration, because passengers arc accelerated by the "space push" along with the rest of the ship. Anomalies exist, off the axis of the ship, and at the rear; but these are canceled or counteracted by properly designed and adjusted auxiliary plates. A combat ship can dart to the sides, too, though not with the acceleration it can achieve along its axis. Due to various limitations of structural materials, power feed, passenger reaction, etc., acceleration (in practice) is limited to about seventeen gees (in normal space, that is). Seventeen gees is not enough to dodge a swarm of computer-coordinated missiles, but it can make them work.

The null drive is something else again. Very soon after development of the new grav-drive technology and science, there were several breakthroughs in understanding the nature of space itself.

The real savants claimed that there must be quite a number of "spaces," each positioned to the others in such a way that time was involved, along with various dimensions. John Braysen was willing to accept that without being harangued at length about it.

There appeared to be no immediate prospect of switching from "normal" space (that is, "our" continuum) to any of the other spaces. However, there was some kind of limbo, or state of existence that was none of the spaces, into which an object could be shifted. The way this was done was awesome: the object (a ship and passengers, for instance) had to have every particle charged with a kind of energy related to, but not identical with, the field that produced gravity shielding. When this charge reached a critical intensity, a little extra surge caused it (to all exterior observations) to cease to exist in normal space. Passengers felt only an instant of odd disorientation.

In this strange limbo (called "null"), ordinary gray drives could accelerate the "ghost" of the ship at a rate fantastically greater than in normal space. That hull acceleration didn't require exceptional power, but to attain readiness for null did. Conduits to feed that power without melting had a practical limitation: the best rate of charging that Earth's or any other known technology could achieve was a little over four minutes.

So you couldn't "break out" of null and reenter immediately.

One of the puzzling things was that the tremendous power thus fed into matter could be discharged so instantly with very little detectable "spill." A little static, a momentary mild blue glow, were the only phenomena yet detected.

Travel in null was not instantaneous. There was a limit of some sort; and, to simplify as much as possible the terrible problems of navigation, the apparatus was standardized to fit some little-understood natural velocity that approximated four hundred and ninety light-years per hour. Usually a ship going, say, one hundred light-years, could judge its breakout point to within one-tenth light-year of its target. From there you made an additional short null hop or hops, like a golfer sinking a putt.

From RECALL NOT EARTH by C.C. MacApp (1970)



Okay, let’s talk about paragravity.

First up, a note on nomenclature. Paragravity is one of the two things that an Imperial habtech might be referring to when they talk about artificial gravity, the other being spin gravity. Unlike spin gravity, which is “powered” by good old centrifugal force, paragravity is produced by ontotechnological space magic that does wonderfully complex things involving information physics and grand unified theories and other such things to poke the universe in exactly the right way – basically, one branch of the mass-inertia-and-momentum manipulating vector control.

Which is to say that it is produced by gravity rotors, suitcase-sized boxes with a power connector, a ‘weave connector, and a thermal management connector on the outside, filled with solid-state hardware that is a proprietary product of Mariseth Gravitics, ICC. And into whose internal workings we shall thus respectfully avoid going.

What we’re talking about here is how they work on the outside.

The field of paragravity (the gravity envelope) can only be created between two gravity rotors of opposed polarity. That gets you a straight field (with perhaps some convex distortion at the edges) between the two, which imposes a force functionally identical to mass-generated gravity (i.e., affecting all atoms, etc., equally) on everything with mass inside it. This creates a consistent down direction towards what, for the sake of designation, we shall call the “positive” rotors.

(You have to have a closed envelope, and can’t operate an unpaired gravity rotor even if you wanted to: since the universe is functionally infinite in whatever direction you’re pointing it, energy requirements for the half-field head asymptotically for infinity, at which point the circuit breakers save you from a messy ‘splosion.)

Both momentum and energy are conserved, as they would have to be.

The former is the reason that you gravity rotors should be bolted firmly to the structure of the hab; whatever force they exert is, per Callaneth’s Lemma (or Newton’s Third Law, whatever name you prefer), reciprocally exerted too, half to each rotor in the pair.

While difficult to arrange even deliberately, this does imply that if you can get enough mass in one spot and move it just right, you can get the gravity rotors to tear themselves free and leap in the appropriate reciprocal direction.

With regard to the latter: it takes energy to establish the gravity envelope, but once it’s up and running, maintaining it takes only minimal energy physically speaking. (I.e., it still consumes quite a bit of energy in the rotor while it’s up and going, because rooting the universe ain’t cheap; that energy just doesn’t go into the envelope. It’s this waste that makes paragravity a real expensive thing to run.)

That, however, is only true so long as nothing is moving within it. Falling objects, moving in the down direction of the envelope, take energy from the envelope as they gain kinetic energy. (Likewise, when you lift an object within the envelope against its downforce, that pushes energy into the envelope, which is a surge effect that the hardware has to cope with. Alas, it’s not something that can be harvested in the majority of applications.) You could call this paragravitational potential energy if you like, since it sits in essentially the same place in the relevant equations.

While it takes the rotors a little while to initialize from a cold start (although some of this time is self-diagnostics and the like), once up and running, though, you can change the parameters of the gravity envelope very quickly; and you can generate pretty much any amount of gravity you want up to their capacity so long as you’re willing to spend the energy (which varies proportionately) needed to do it.

This is what lets you use the exact same technology for inertial damping; you just have appropriately oriented gravity rotors cancel out your engine thrust inside the starship – while bearing in mind that this will have certain effects on your structural load. (Likewise, you can use them when grounded – but since they don’t block planetary gravity, if you want 1G in the cabin when landed on a 3G world, you will actually be running the paragravity system at -2G.)

The drawback, however, is that the same lack of “inertia” in operation that lets you change your gravity quickly means that they fail equally quickly – and shut down essentially instantly if the power fails, just like an electromagnet’s field collapses – so failing to keep up maintenance schedules may mean being abruptly smashed to the deck with a force of twelve gravities! Caveat engineer.

Cities in Flight

James Blish's classic Cities in Flight series have paragravity machines called Dillon-Wagoner Graviton Polarity Generators (commonly called "Spindizzies"). They use the (now discredited) Blackett effect aka "gravitational magnetism". Control the spin and you control the gravity. In the novel it has lovingly constructed baffle-gab explanations with just enough real science to stub your toe on and fool you into thinking it is actually plausible. The joker in the deck is that the efficiency of a spindizzy goes up as the mass of the spacecraft increases. The novels center around entire cities uprooted and turned into starships via spindizzies, turning into interstellar migrant laborers escaping the economic collapse of Terra. In the latter novels, entire planets are moved with spindizzies.


“Sure. It’s a thing called the Blackett equation. Deals with a possible relationship between electron-spin and magnetic moment. I understand Dirac did some work on that, too. There’s a G in the equation, and with one simple algebraic manipulation you can isolate the G on one side of the equals-sign, and all the other elements on the other.” (Not a crackpot notion this time. Real scientists have been interested in it. There’s math to go with it.)

“Status?” (Why was it never followed, then?)

“The original equation is about status seven, but there’s no way anybody knows that it could be subjected to an operational test. The manipulated equation is called the Locke Derivation, and our boys say that a little dimensional analysis will show that it’s wrong; but they’re not entirely sure. However, it is subject to an operational test if we want to pay for it, where the original Blackett formula isn’t.” (Nobody’s sure what it means yet. It may mean nothing. It would cost a hell of a lot to find out.)

“Do we have the facilities?” (Just how much?)

“Only the beginnings.” (About four billion dollars, Bliss.)

“Conservatively?” (Why so much?)

“Yes. Field strength again.”

(That was shorthand for the only problem that mattered, in the long run, if you wanted to work with gravity. Whether you thought of it, like Newton, as a force, or like Faraday as a field, or like Einstein as a condition in space, gravity was incredibly weak. It was so weak that, although theoretically it was a property of every bit of matter in the universe no matter how small, it could not be worked with in the laboratory. Two magnetized needles will rush toward each other over a distance as great as an inch; so will two balls of pith as small as peas if they bear opposite electrical charges. Two ceramet magnets no bigger than doughnuts can be so strongly charged that it is impossible to push them together by hand when their like poles are opposed, and impossible for a strong man to hold them apart when their unlike poles approach each other. Two spheres of metal of any size, if they bear opposite electrical charges, will mate in a fat spark across the insulating air, if there is no other way that they can neutralize each other.

(But gravity — theoretically one in kind with electricity and magnetism — cannot be charged on to any object. It produces no sparks. There is no such thing as an insulation against it — a di-gravitic. It remains beyond detection as a force, between bodies as small as peas or doughnuts. Two objects as huge as skyscrapers and as massive as lead will take centuries, to crawl into the same bed over a foot of distance, if nothing but their mutual gravitational attraction is drawing them together; even love is faster than that. Even a ball of rock eight thousand miles in diameter — the Earth — has a gravitational field too weak to prevent one single man from pole-vaulting away from it to more than four times his own height, driven by no opposing force but that of his spasming muscles.)

Now all this seemed to me to have nothing to do at all with gravity, and I said so to my team chief, who brought the thing to my attention. But I was wrong (I suppose you’re already ahead of me by now). Another man, Prof. P. M. S. Blackett, whose name was even familiar to me, had pointed out the relationship. Suppose, Blackett said (I am copying from my notes now), we let P be magnetic moment, or what I have to think of as the leverage effect of a magnet — the product of the-strength of the charge times the distance between the poles. Let U be angular momentum — rotation to a slob like me; angular speed times moment of inertia to you. Then if C is the velocity of light, and G is the acceleration of gravity (and they always are in equations like this, I’m told), then:

P = BG½U / 2C

(B is supposed to be a constant amounting to about 0.25. Don’t ask me why.)

Admittedly this was all speculative; there would be no way to test it, except on another planet with a stronger magnetic field than Earth’s — preferably about a hundred times as strong. The closest we could come to that would be Jupiter, where the speed of rotation is about 25,000 miles an hour at the equator — and that was obviously out of the question.

Or was it? I confess that I never thought of using Jupiter, except in wish-fulfillment daydreams, until this matter of the Locke Derivation came up. It seems that by a simple algebraic manipulation, you can stick G on one side of the equation, and all the other terms on the other, and come up with this:

G = (2PC / BU)2

To test that, you need a gravitational field little more than twice the strength of Earth’s. And there, of course, is Jupiter again. None of my experts would give the notion a nickel — they said, among other things, that nobody even knew who Locke was, which is true, and that his algebraic trick wouldn’t stand up under dimensional analysis, which turned out to be true — but irrelevant. (We did have to monkey with it a little after the experimental results were in.) What counted was that we could make a practical use of this relationship.

Once we tried that, I should add, we were astonished at the accompanying effects: the abolition of the Lorentz-Fitzgerald relationship inside the field, the intolerance of the field itself to matter outside its influence, and so on; not only at their occurring at all — the formula doesn’t predict them — but at their order of magnitude. I’m told that when this thing gets out, dimensional analysis isn’t the only scholium that’s going to have to be revamped. It’s going to be the greatest headache for physicists since the Einstein theory; I don’t know whether you’ll relish this premonitory twinge or not.

"But the one job that only the Bridge could do was that of confirming, or throwing out, the Blackett-Dirac equations.”

“Which are—?”

“They show a relationship between magnetism and the spinning of a massive body — that much is the Dirac part of it. The Blackett Equation seemed to show that the same formula also applied to gravity; it says G equals (2PC / BU)2, where C is the velocity of light, P is magnetic moment, and U is angular momentum. B is an uncertainty correction, a constant which amounts to 0.25.

“If the figures we collected on the magnetic field strength of Jupiter forced us to retire the equations, then none of the rest of the information we’ve gotten from the Bridge would have been worth the money we spent to get it. On the other hand, Jupiter was the only body in the solar system available to us which was big enough in all relevant respects to make it possible for us to test those equations at all. They involve quantities of infinitesimal orders of magnitudes.

“And the figures showed that Dirac was right. They also show that Blackett was right. Both magnetism and gravity are phenomena of rotation.

“I won’t bother to trace the succeeding steps, because I think you can work them out for yourself. It’s enough to say that there’s a drive-generator on board this ship which is the complete and final justification of all the hell you people on the Bridge have been put through. The gadget has a long technical name — The Dillon-Wagoner gravitron polarity generator, a name which I loathe for obvious reasons — but the technies who tend it have already nicknamed it the spindizzy, because of what it does to the magnetic moment of any atom — any atom within its field.

“While it’s in operation, it absolutely refuses to notice any atom outside its own influence. Furthermore, it will notice no other strain or influence which holds good beyond the borders of that field. It’s so snooty that it has to be stopped down to almost nothing when it’s brought close to a planet, or it won’t let you land. But in deep space well, it’s impervious to meteors and such trash, of course; it’s impervious to gravity; and it hasn’t the faintest interest in any legislation about top speed limits. It moves in its own continuum, not in the general frame.”

“You’re kidding.” Helmuth said.

“Am I, now? This ship came to Ganymede directly from Earth. It did it in a little under two hours, counting maneuvring time. That means that most of the way we made about 55,000 miles per second — with the spindizzy drawing less than five watts of power out of three ordinary No. 6 dry cells.”

“The fundamental equation of the Blackett-Dirac scholium reads as follows:

P = BG½U / 2C

where P is magnetic moment, U is angular momentum, C and G have their usual values, and B is a constant with the value 0.25 approximately. A first transform of this identity gives:

G = (2PC / BU)2

which is the usual shorthand form of the primary spindizzy equation, called the Locke Derivation. Blackett, Dirac and Locke all assumed that it would hold true for large bodies, such as gas-giant planets and suns. Show on the blackboard by dimensional analysis why this assumption is invalid.”

As far as Chris was concerned, the answer could have been much more simply arrived at; Dr. Braziller could just have told him that this relationship between gravitation and the spin of a body applied only to electrons and other submicroscopic objects, and disappeared, for all practical purposes, in the world of the macrocosm; but that was not her way. Had she only told him that, it would have come into his mind as a fact like any other fact — for instance, like the facts that the memory cells of the City Fathers were constantly pouring into his ears and eyes — but by her lights he would not have understood it. She wanted him to repeat not only the original reasoning of Blackest, Dirac and Locke, but to see for himself, not just because she told him so, where they had gone astray, and hence why a natural law which had first been proposed in the gas-lit, almost prehistoric year of 1891, and was precisely formulated as the Lande Factor in 1940, nevertheless failed to lift so much as a grain of sand off the Earth until the year 2019.

From CITIES IN FLIGHT by James Blish (1956)

James Blish’s famous “cities in flight” series, first published in the Astoundings of the 1950s and later collected in Cities in Flight (Avon, 1970), used a device called a spindizzy (or “Dillon-Waggoner gravitron polarity generator”), a wondrous contraption that used principles from the “Blackett-Dirac equations” to transform rotation and magnetism into gravitational attraction or repulsion, making enough antigravity to lift whole cities and in the bargain providing impenetrable shielding and faster-than-light travel, Both spindizzy and Blackett-Dirac equations were purely the products of Blish’s far-ranging imagination, but the work of P.M.S. Blackett is real.

Blackett was a prominent British astronomer who noticed a correlation between the rotation rates, the gravitational fields, and the magnetic fields of the Sun, Earth, and Jupiter. In a paper in the British joumal Nature, Blackett presented an empirical equation relating these quantities. He went on to suggest that there might be a previously unsuspected principle of nature by which magnetic fields are generated directly in massive electrically neutral rotating bodies like the Earth.

A few years later, a science fact article in John W. Campbell’s Astounding Science Fiction described Blackett’s work as the possible discovery of a new law of nature. The author of that article suggested that if gravity and rotation could produce magnetism, then rotation and magnetism might produce gravity and even antigravity. With some nudging from Campbell, James Blish picked up Blackett’s ball and ran with it. Hence, the spindizzy.

In the SF of James Blish the ideas of Blackett lead to the stars, but unfortunately they never got off the ground in the real world of physics and astronomy. Improved measurements of the magnetic fields of various objects in the Solar System did not fit the predictions of Blackett’s “law,” nor did the geological evidence that the terrestrial magnetic tield undergoes periodic reversals. The present “standard” explanation of planetary magnetism is that in the liquid cores of planetary objects are dynamic currents that are coupled like dynamos to the planetary rotation. These currents generate the magnetic fields of the objects.

Over the recent 1989 Christmas holidays, however, it appeared that the spindizzy and gyro-gravity might be due for a renaissance. A paper entitled “Anomalous Weight Reduction on a Gyroscope’s Right Rotations about the Vertical Axis on the Earth” appeared in the December 18, 1989 issue of the journal Physical Review Letters. It is the work of two Japanese physicists, Hideo Hayasaka and Sakae Takeuchi of the department of radiation engineering, Tohoku University, in Sendai, Japan. The paper presented detailed evidence that three different motor-driven gyroscope rotors made of brass, aluminum, and silicon-steel each showed a weight loss of up to 12 milligrams (weight) or a few parts in 100,000 in overall weight when the gyro was spun clockwise (as viewed from above) at between 3 and l3 thousand RPM. The gyros showed no weight-loss effect when spun counter-clockwise. The clockwise-spin data showed that the weight loss of the gyro depends linearly on the rotation rate of the gyro. The weight loss data is very regular. ln fact, it is too regular for strict consistency with the error bars of the experimental data points. The Hayasaka-Takeuchi paper was careful to emphasize that no known physical effect, including general relativity, can account for an effect of this size and rotational dependence.

There was a considerable delay before the gyro-gravity paper actually appeared in print. It was first submitted to the rapid publication journal Physical Review Letters (PRL) on March 7, 1988, but it required an additional 21 months before it appeared in PRL, a journal which ordinarily published within 4-8 weeks after submission. Reportedly the paper was delayed because the PRL editors and referees were very skeptical of the reported effect but could find nothing wrong with the. experimental techniques described. After repeated revision of the paper, some re-refereeing, and much editorial deliberation, the paper was finally published.

As soon as it appeared, science-oriented journalists were quick ,to realize the anti-gravity implications of gyrogravity. In late December they conducted an intensive telephonic search for scientists and others who were willing to provide quotable comments on the work. This search was made more difficult because most universities and many government laboratories were closed for holidays. One of the most memorable comments on gyro-gravity reported in the press came from “a noted UFO expert,” who said that the result must be correct because it is well known in UFO circles that the engines of flying saucers work by gyro-gravity.

Scientists among the quoted “experts” tended more toward skepticism and caution. Many said that the effect must be reproduced in other laboratories before it could be taken seriously. There were also some feelings that the Japanese result was likely to be wrong because it had a very peculiar and unphysical spatial dependence—it did not change sign when the gyro’s spin direction was reversed but instead went to zero.

At a small number of laboratories, experiments were set up to test whether the Hayasaka-Takeuchi effect could be reproduced. There was less of a “gold rush” atmosphere about these experiments than had been the case with the cold fusion furor of the previous year. Perhaps this is because there was more skepticism that the effect was real. Or perhaps the expensive equipment and manpower investment in cold fusion negative results of last year has made the scientific community more cautious about “table-top” experiments with spectacular results.

In any case, the results from a few follow-up experiments to test the Hayasaka-Takeuchi effect have now began to appear. A group at the University of Colorado in Boulder and the National Institute for Science and Technology (formerly the National Bureau of Standards) has reported in a paper that has just been accepted by Physical Review Letters. To within their observed error of ±0.5 milligrams, the Boulder group observed no weight loss of the gyro and no dependence on whether its vertical rotation was clockwise or counter-clockwise. They used a brass rotor with a hardened steel shaft rotated at speeds between 1,000 and 9,000 RPM. The rotor turned on jeweled bearings. lt had about three times the mass of the rotors used by Hayasaka and Takeuchi and an overall sensitivity to the reported effects that was about 10 times greater. There were, of course, other differences in method. The Boulder experiment had very little magnetic material in the gyro, placed it in a Lucite chamber, spun it up with a jet of compressed nitrogen blown tangenially on a nylon gear, and did not evacuate the chamber. Hayasaka and Takeuchi used an integral electric motor to drive their rotor (which included magnetic material). The gyro rotated on ball bearings and was enclosed in an evacuated steel container. In a related paper that has just appeared in the journal Nature, Dr. S. H. Salter, a mechanical engineer at the University of Edinburgh, presents calculations showing that the Hayasaka-Takeuchi observations might be explained by the action of vibrations from the rotating gyro on the ball bearings of the appa- ratus.

Thus, at present gyro-gravity seems to be in trouble. The effect has not been reproduced with similar apparatus, and the observed effects might plausibly result from vibrations. I would hope, however, that before the laboratory tests are abandoned altogether, someone will try using a rotor Which, like the one in the Haylasaka-Takeuchi apparatus, contains significant magnetic material. As we SF readers know, a proper spindizzy requires rotation and magnetism to operate properly.

From THE RISE AND FALL OF GYRO-GRAVITY by John G. Cramer (1990)

Tales Of The Flying Mountains

In Poul Anderson's Tales of the Flying Mountains, the solar system is opened up by the discovery of "gyrogravitics" (geegees). Mr. Anderson was probably inspired by Blish's spindizzies, since "spin" and "gyro" are related terms. In the stories, it started off as the director of NASA investigating a crack-pot theory as busy-work in a desperate effort to keep NASA alive until the director could retire. The director was pretty sure it was a dead end, but didn't care since it would keep Congress from killing NASA for a few years. By the time the research crashed and burned the director expected to be safely retired.

Then the Soviet space agency started studying it (probably for the same reason). This sparked an arms race, and the money poured in. The nations could not afford to have a gyrogravitics gap! Amazingly, it actually resulted in a working space drive and a tractor beam. The solar system was inadvertently opened up by two bureaucrats just trying to hang on to their jobs.

Amusingly enough, the tractor beam obeyed a super-duper inverse square law: it had a range of only a few centimeters. It worked, but the ship with the tractor had to be practically in contact with the object it was moving.

"I'm delighted to explain. Have you heard of gyrogravitics?"

Stanhope shook his knaggy head. Carter of Virginia said, slowly, "Has to do with atomic theory, doesn't it."

"That's right," Harleman answered. "I don't claim to follow the mathematics myself, but I've had scientists give me a lay explanation. It grew out of the effort to reconcile relativity and quantum mechanics. Those two branches of physics, both indispensable, were at odds on certain fundamental questions. Is nature or is nature not deterministic—describable by differential equations? Well, you may have read how Einstein once declared he couldn't believe that God plays dice with the world, while Heisenberg thought cause-and-effect was nothing but the statistics of large numbers, and Bohr suggested in his complementarity principle that both views might be true. Later, building on the work of such as Dyson and Feinberg—" Harleman saw them drifting away again. Damn! I spent too much time with Emett last night. That jargon of his soaked into my skin.

"Well, the point is, gentlemen," he said, "in the newest theory, matter and energy are described by their properties from the equations, equations like those of a rotating force-field. Including gravitation."

Carter jerked to an upright sitting position. "Wait a minute!" he exclaimed. "You aren't leading up to antigravity, are you? I happen to know what the Air Force has been doing in that line for the past fifty years. It's no secret they've drawn absolute blanks. Antigravity belongs with witches on broomsticks. I could reach Mars easier by ... by astral projection."

"Not antigravity, sir," Harleman told him. "Gyrogravitics."

"A change of labels doesn't—"

"Please sir. I've had some most interesting discussions with a Mr. Quentin Emett. Some of you may have heard of him: an independent investigator—"

"Means he hasn't got his Ph.D.," Thomasson said grimly.

"Well, yes, he does happen to lack a union card," Harleman replied.

"Mr. Emett's ideas are unorthodox, true. He proposes to develop a generator which, by means of nuclear resonance rotations, will create fields that we can call gravitational, or antigravitational, or pseudogravitational, or whatever we like. I think 'gyrogravitic' is probably the best word, though if we can get this work authorized, the R and D effort should have a more suitable name such as, for example, Project Dyna-Thrust."

Carter sneered. "And you'll make your spaceships weightless and float them right off Earth, eh?"

"No, sir." Emett had carefully rehearsed Harleman. "Conservation of energy and momentum are not violated. In effect, a gyrogravitic drive should react against the entire mass of the ambient universe. You'll still need power to rise, or accelerate, or maneuver in any other way. But it'll be minimum power; you won't be throwing energy out in exhaust gases. The power plant can be minimal too; since you can hover free, or nearly free, you don't need a huge motor to raise you as fast as possible. Any energy source will do—fuel cells, batteries, nuclear reactors, I suppose even steam engines—though no doubt as a side benefit we'll get small, portable fusion plants. A ship like this would be almost one hundred percent efficient, silent, unpolluting, economical to build, capable of going anywhere. The capability would derive in part from interior gyrogravitic fields. These would provide weight though the ship be in free fall, cushion against pressure when it accelerates, ward off solar-storm particles, meteoroids, and similar hazards." Harleman ratcheted up his enthusiasm. "In short, gyrogravitlcs can give us the whole Solar System."

"So can sorcery," Carter grumbled, "if only we can discover how to make it work."

Harleman talked nominally to them all, actually to Stanhope: "My belief is, the United States can't write off its huge investment in NASA, and in any case, positively not overnight. Research must go on. One advantage of Mr. Emett's proposal is its modest cost. If we establish Project Dyna-Thrust, it should be feasible to discontinue various other activities and thus reduce the total budget—without feeling that we have broken faith with our predecessors or abandoned the Endless Frontier of Science."

From "Nothing Succeeds Like Failure" collected in TALES OF THE FLYING MOUNTAINS by Poul Anderson (1970)

Carrot On A Stick

This is a surprisingly common piece of handwavium found in science fiction to use paragravity for spacecraft propulsion. The word "handwavium" is a clue that this is utter bilge.

Remember the old "carrot on a stick" trick? You sit on a horse or donkey. You use a stick to dangle a carrot in front of the animal's nose. It then walks forward trying to get the carrot. Since it never gets any closer, it keeps on walking until it collapses. TV tropes calls this "Motivation on a Stick."

The idea is your spacecraft (the donkey) is equipped with a magic handwavium paragravity device (the stick) that creates a bodiless point source of gravity (the carrot) a couple of meters in front of your spacecraft's nose. With lots of gravity. The ship and everything in it falls into the point gravity source. But this includes the paragravity gizmo. Which means the point gravity source moves forward, exactly like the carrot is moved forward by the stick. The ship keeps accelerating until the paragravity gizmo runs out of electricity.

The advantages is that the ship and everything is being accelerated by the force of gravity, which acts on all the atoms equally. Meaning that the ship can accelerate at 500 gees without turning the crew into wall-gazpacho. Heck, at 500 gees the crew is still floating in free fall.

You can also use this to alter your vector. On your donkey, you can make it turn to the right by manipulating the stick so the carrot moves to the right. This allows you to steer the donkey. In a similar manner, you can use the paragravity gizmo to change the position of the point gravity source. Make it appear to starboard, and the ship will start accelerating in that direction. Make it appear in the opposite direction of the ship's current vector for deceleration.

The disadvantage is it won't work.

First off there is the sticky problem of the "stick", meaning how do you push the point gravity source forwards so the ship does not ram it? If you push it forwards with 500 gees, Newton will insist that the reaction pushes the ship backwards with 500 gees. So the net result is the ship just sit there.

If instead of a point gravity source you are using a physical paragravity machine, the machine will be attracted to the ship with the same force as the ship will be attracted to the machine. They will ram each other. But if you mount the machine on a framework attached to the ship's nose to prevent ramming, then the machine's gravity will attract the ship with a force of X while the machine's motion transmitted through the framework will push back with a force of -X, and the net motion will be X - X = 0.

This is similar to that tired old gag of propelling a sailboat by blowing on a sail with an electric fan. The wind from the fan will hit the sail, the action pushing the boat forward. Alas, the reaction on the fan from expelling the wind will move the fan backwards. If the fan is bolted to the sailboat, the action and the reaction will cancel out. Net motion of zero. If the fan is not bolted to the boat, it will go flying backwards and fall off the aft end. (Airboats do not count since the fan is not blowing on a sail attached to the boat, it is purely using the reaction of expelling the air)

Common hand-waves desperately used at this point are either [a] bodiless point sources of gravity have no inertia or [b] the gravity point is created and held in existence only long enough to yank the ship. Then a new point is created a bit further ahead. The ship moves forward in stroboscopic jerks. In William Keith's Star Carrier series, this is done by a control on the gravity generator called a bootstrapper.

The entire drive comes under the heading of pulling yourself up by your own bootstraps. Much in the same way Baron Munchausen lifted himself and his horse out of the swamp and into the air, by pulling upwards on his pigtail.

But the major problem is that while paragravity is technically unobtainium, all the plausible techniques have the created gravity field centered inside the gizmo. Not at some distance away.

Be that as is may, there are quite a few science fiction novels that use this contraption.

Invaders from the Infinite by John W. Campbell jr. (1961)
The attractive ray makes a section of the mesh of the space-time continuum emit gravity waves. This can be used to move a ship, asteorid, planet, star, or whatever you have the energy for. Since the gravity is coming from the mesh of space, the attractive ray violates Newton's law of action and reaction. Total handwavium.
The Tar-Aiym Krang by Alan Dean Foster (1972)
Kurita-Kita gravity drive ships look like a balloon stuck on the handle of a plumber's helper. The "suction cup" is the ship's nose, the balloon is to the rear. The suction cup is the gravity field generator, the balloon is the habitat and payload module. It operates like a standard carrot-on-a-stick drive.

In addition, in some handwaving way near lightspeed it generates a "cone shaped region of stress" that in some manner allows the ship to travel faster than light. Captains are encourage not to enter FTL travel while inside a solar system, since at that point the gravity field has the mass of a good sized sun and could alter the orbits of the planets. Hmmmm, sounds like a huge case of Jon's Law to me.
The Ring of Charon by Roger MacBride Allen (1990)
The Charonian aliens gravity technology can accelerate and levitate large masses by creating artificial gravitational point sources. But while natural gravitation sources are isotropic, the gravity of artificial gee points can be confined to narrow beams.
Path of the Fury by David Weber (1992)
The Fasset drive creates a black hole in front of the ship, which the ship falls into. But the generators move with the ship, pusing the black hole ahead. Standard carrot-on-a-stick drive.
Man-Kzin Wars VIII: Choosing Names edited by Larry Niven (1998)
I have not read this collection, I am getting my information second hand. In Larry Niven's original Kzin stories, the Kzinti use the "gravity planar" aka "gravity polarizer" for propulsion. But apparently one of the authors in this collection didn't get the memo, and invented a totally non-canon propulsion system that was basically a carrot-on-a-stick drive. The author specified that the gizmo used magnetic monopoles in its construction since those are a signature Larry Niven touch.
Earth Strike: Star Carrier by Ian Douglas (William H. Keith, Jr.) (2010)
The spacefighters project a point gravity source capable of accelerating the fighter at 50,000 gees. They can accelerate close to c in about ten minutes flat. In combat though they keep to much slower velocities otherwise aiming their weapons would be impossible. The fighters are crazy maneuverable since the point gravity source can be instantly positioned anywhere to alter the ship's vector in any direction at 50k g.

The huge capital ships and carriers cannot use this drastic propulsion because they are about a kilometer long. At 50k g the gravity gradient across a twenty meter fighter is negligible. But the gradient across a one kilometer battleship will create tidal forces capable of ripping the ship apart.
Gargantia on the Verdurous Planet by Wataru Mitogawa (2013)
The Machine Caliber combat mecha fly by using "artificial gravity sinks." This is a very maneuverable carrot-on-a-stick drive, since a gravity sink can be created at any position nearby the Machine Caliber.

      He got only the slightest glimpse of their ship, the Gloryhole. That was enough.
     Sandwiched in among bloated freighters and pudgy transports she looked like a thoroughbred in a barnyard. She still had the inevitable shape of a doublekay (Kurita-Kita) drive ship, a balloon stuck on to the end of a plumber’s helper, but the lines were different from most. The balloon at one end was the passenger and cargo space, and the plunger at the other the generating fan for the posigravity field. Instead of being wide and shallow, like a plate, the Gloryhole’s generating fan was narrower and deep, chalicelike. The passenger-cargo area was still balloon-shaped, but it was a streamlined, tapered balloon. Simply on looks alone one could tell that the Gioryhole was faster than any regular freighter or liner aspace.

     ‘Oh, there’s no real danger from change over. The companies like to make a big thing of it to give their passengers a slight thrill. Sure, once in a while you’ll hear about something happening. A meteor will make a millions-to-one infringement on the gravity well of a ship at the moment of shift and the ship will turn inside out, or something equally weird. Those are real exceptions.

     ‘I’ve never been on a doublekay drive ship before. I’m no physicist, but could you maybe give me a quickee explanation of how the thing works? One that even my simple mind could understand’?’
     She sighed. ‘Okay. What the Caplis generator does … that’s what we hold in the “fan” up ahead … is in effect produce a powerful but concentrated gravitational field at the nose of the ship. As soon as the field exceeds the natural one of the ship, the ship moves towards it, naturally attracted by a “body” of greater “mass” than itself. Being part of the ship, the doublekay drive unit naturally goes along with it. But the unit, having moved forward, is set to keep the field at a constant distance from the hull of the craft.
     Therefore the field is moved forward also. The ship will try to catch up to it again, and so on, ad infinitum. The field is in effect pulling the ship instead of pushing it, as the shuttle rockets do, Doublekay vessels actually move in a series of continuous jerks, so rapid and close together that they seem to be one smooth, unbroken pull. The increase or decrease in the size of the field determines the speed of the ship.
     ‘Being a wave and not a particle form of energy, gravity isn’t affected in the same way that mass is on approaching the speed of light. The doublekay field creates a coneshaped zone of stress behind it, in which mass acts differently than it does under normal circumstances. That’s why when we exceed the speed of light I don’t see through you or something. Once we’ve made that initial breakthrough, or “change over,” our rate of travel goes up enormously. It’s something like riding the back of a very tame SCCAM shell.
     ‘Our initial power comes from a small hydrogen “spark-plug” … I wonder sometimes where that word came from … up near the generator housing in the tube section of the ship. Once started up, the field can be “channelled” to a certain extent. That’s where we get our gravity for the ship and power to run the lights and a lit o bar and things.
     “In the event of a drive failure there are provisions for converting the fan loan old ion-type drive, powered by the hydrogen plug. It would take twelve years at its best speed to get from Moth to Power Line, the nearest inhabited planet. Farther out where the stars are more scattered it’s even worse. But twelve years or so is better than never. Stranded ships have been saved that way … those that managed to overcome problems like lack of food and insanity. But the rate of failure for doublekay drives in miniscule. Only rarely can a mere human manage to screw one up.’

From THE TAR-AIYM KRANG by Alan Dean Foster (1972)

      “Blue Omega Strike, Omega One,” Allyn said over the squadron’s tac channel. “Engage squadron taclink.”
     Gray focused a thought, and felt an answering sensation of pressure in the palm of his left hand. The twelve fighter craft were connected now by laser-optic comnet feeds linking their on-board AIs into a single electronic organism.
     “And gravitic boost at fifty kay,” Allyn continued, “in three…two…one…punch it!”
     A gravitational singularity opened up immediately ahead of Gray’s Starhawk.
     He was falling.
     In fact, he was accelerating now at fifty thousand gravities, falling toward the artificial singularity projected ahead of his gravfighter, but since the high-G field affected every atom of the Starhawk and of Lieutenant Gray uniformly, he was not reduced to a thin organic smear across the aft surfaces of the cockpit. In fact, he felt nothing whatsoever beyond the usual and somewhat pleasant falling sensation of zero gravity.
     Outwardly, there was no indication that within the first ten seconds of engaging the gravitic drive, he was traveling at five hundred kilometers per second relative to the America, his speed increasing by half a million meters per second with each passing second. The stars remained steady and unmoving, unwinking in the night.
     After one minute he’d be traveling at three thousand kilometers per second, or 1 percent of the speed of light.
     And in ten minutes he’d be pushing hard against c itself.

     Vector changes in space-fighter combat were a lot trickier than for an atmospheric fighter; they were possible at all only because gravitic propulsive systems allowed the fighter to project a deep singularity above, below, or to one side or the other relative to the craft’s current attitude. Intense, projected gravity wells whipped the fighter around onto a new vector, bleeding off velocity to throw an extra burst of power to the inertial dampers that, theoretically at least, kept the pilot from being squashed by centripetal acceleration.
     Enough gravities seeped through the straining damper field to press Gray back against the yielding nanofoam of his seat; stars blurred past his head.

     “Does that mean we’re going to do a skew-flip, Admiral? To start decelerating?”
     “No, sir, it does not. You’re thinking of the gravitic drives on the fighters. The Alcubierre Drive works differently…an entirely different principle.”
     “I don’t understand.” Koenig wondered if that man had been briefed at all…or if he’d been given a technical download that he’d failed to review. Quintanilla seemed to read Koenig’s expression. “Look, I’m here as a political liaison, Admiral. The technology of your space drive is hardly my area of expertise.”
     Obviously, Koenig thought. “The type of gravitational acceleration we use on the fighters won’t work on capital ships,” he said, “vessels over about eighty meters in length. With ships as large as the America, projecting an artificial singularity pulling fifty-kay gravs or so ahead of the vessel would cause problems—tidal effects would set up deadly shear forces within the ship’s hull that would tear her to bits.
     “So for larger ships, we use the Alcubierre Drive. It manipulates the fabric of spacetime both forward and astern, essentially causing space to contract ahead and expand behind. The result is an enclosed bubble of spacetime with the ship imbedded inside. The ship is not accelerating relative to the space around it, but that space is sliding across the spacetime matrix at accelerations that can reach the speed of light, or better.”

     The beam caught his Starhawk aft, slashing through shields, vaporizing critical portions of the gravfighter’s projection bootstrappers.
     Fighters under drive fell toward an artificial gravitational singularity projected in the desired direction of acceleration; bootstrapper was the slang term for the electronics that continually refocused the singularity ahead of the ship from picosecond to picosecond. With the bootstrapper disabled and the singularity still powered, Sandoval’s Starhawk fell into its own drive field, its nose crumpling as the fighter began whipping around the pinpoint singularity in a high-velocity blur. In another instant, about a quarter of the fighter was consumed, smashed down into subatomic debris at the singularity’s event horizon. The rest sprayed into surrounding space, most of the mass transformed into a blinding flash of energy.
     The remaining four members of the Dragonfires continued the attack.

From EARTH STRIKE by William H. Keith, Jr. (under pseudonym Ian Douglas) (2010)

(ed note: Coyote Westlake is an rock-rat whose habitat module is currently attached to her claim on tiny asteroid AC125DN1RA45. When she regains conciousness, she finds the asteroid is under acceleration)

      Coyote Westlake woke up with a pounding headache, slumped in a corner of her habitat shed. What the hell had she been drinking last night?

     Lying there without moving a muscle, she carefully reviewed the night before. Wait a second, she thought. I didn’t have anything to drink. I haven’t had a drink in weeks. There was a very good reason for that: there wasn’t a drop of booze left in the hab shed or the ship.

     Clearly something was wrong. She had to think this out. But the reflexes of an experienced drinker had taught her to keep her eyes shut when she found herself in this sort of position, being careful not to move a muscle while she took stock of her situation. Getting up and moving was a quick invitation to particularly messy forms of vertigo — especially in zero gee. She lay still, eyes shut, and tried to remember.

     If she hadn’t been drinking the night before, then this was not a hangover. She had gone to bed early and stone cold sober, in a good mood even. Then what the hell had happened? She needed more data. She cautiously opened one eye, and then the other, and found herself staring at what seemed to be the forward bulkhead of the hab shed, at the far end of the cabin from her bunk. She was pasted, facedown, to the wall of the shed. She realized her nose was somehow both numb and sore at the same time, and the pain in her head was across her forehead. She must have slammed herself facefirst into the wall somehow. That, as least, would explain the headache — but how the hell had she thrown herself across the cabin? Even in zero gee, it was a hell of a stunt. Had she leapt out of bed during a nightmare?

     Moving cautiously to avoid the stomach-whirling nausea she still half-expected, she reached out with both her hands and pushed herself away from the bulkhead. She drifted back away from the wall — and then was astonished to find herself drifting back down toward it. No, not drifting — falling. She scrambled in midair and managed to swing herself around fast enough to land, rather awkwardly, on her rump rather than her face again. Falling? In zero gee? Not zero anymore. She would estimate it as about a twentieth gee or so (5% of a gee).

     She sat there, staring at the cabin above her — above her — in utter bewilderment. Her bunk was bolted to the aft wall of the cabin — which had now become the ceiling. The sheet was caught by one of the restraint clips, or otherwise it would have fallen too. Now it hung absurdly down. She glanced around the forward bulkhead she was sitting on and found it littered with bits and pieces of equipment that had slammed down with her. She reached up and felt a bump on the top of her head. Something must have clipped her as it fell.

     She stood up, as carefully as she could, and tried to think. When she had gone to sleep, her hab shed had been bolted to the side of asteroid AC125DN1RA45, a tiny hunk of rock less than half a kilometer across, far too small to generate any gravity field worth mentioning. Maybe a ten-thousandth of a gee, tops. Now, suddenly, she was in a gee field hundreds of times stronger than that. What the hell was going on? Had someone moved her hab shelter for some reason?

     Her shelter was a cylinder about fifteen meters long. Or, now, fifteen meters tall, with Coyote standing on the bottom looking up. At its midsection was an airlock system. There were two viewports at the midsection as well, one set into the airlock and the other set into the bulkhead opposite. One port afforded a view of the asteroid’s surface, the other a view spaceward. What she couldn’t see through the ports she ought to be able to see using the remote-control exterior camera. The camera’s controls were set into the wall by the airlock.

     It took her two or three tries, and two or three crashes, before she managed to jump precisely enough to grab a handhold by the airlock and clip herself into place with the restraint belts intended for holding small pieces of cargo. She looked through the rockside port first and breathed a sigh of relief. RA45’s dark bulk was still there. She recognized not only the rumpled landscape, but her own mining gear. And there was the drill pit down into the rock’s interior.

     Then she looked out the spaceward viewport and discovered something was missing after all. Not on the rock. In the sky.

     In a horrifying flash she realized what she wasn’t seeing. Her ship. The Vegas Girl was gone. No, wait a second. There it was, a tiny blinking dot of light far to sternward, the Girl’s tracking strobe.

     How the hell could this have happened? She had left the Vegas Girl in a perfectly matched orbit relative to RA45. There was no way she could have drifted that far while Coyote was asleep.

     Unless she had been sleeping for one hell of a long time. She checked her watch and compared it to the time display on the hab shed’s chronometer. She even checked the date, just to be sure she hadn’t slept around the clock. But no, she had been out only a few hours. How far had her ship drifted?

     Coyote grabbed the radar range-and-rate gun out of its rack and aimed it through the spaceward viewport, lining up the sights on the Girl. It was a low-power portable unit, not really meant to work at long range. Normally she used it to establish distance from and velocity toward an asteroid, but it could track her ship just as handily. She got the blinking strobe in the sights and pulled the trigger. The gun pinged cheerfully twice to indicate it had gotten a good range and rate on its target. Coyote checked the gun’s tracking data display. And her heart nearly stopped. The Vegas Girl was over one hundred kilometers astern, and the ship was moving away at over three hundred meters a second.

     But wait a moment. The tracker just showed relative velocity, not which object was doing the moving. She peered out the port again, and spotted the triple-blink beacon she had left on RA46, the last rock she had worked. She swore silently. RA46 was in the wrong part of the sky. She fired a ranging pulse at it and got back virtually the same velocity value. The Girl was stationary relative to RA46. So it wasn’t the ship moving. It was this rock. It was moving at nearly twelve hundred kilometers an hour relative to the ship! But how the hell—

     Good Golly God. She wasn’t in a gravity field — that was a one-twentieth-gee acceleration she was feeling. But for how long? Coyote knew that velocity could accumulate at a hellacious rate under even modest acceleration.

     Even so, she was startled by the results when she ran the problem. Assuming one-twentieth gee (5% of a gee), that meant the rock had been accelerating for only ten or eleven minutes. Somehow, the numbers were the most frightening thing.

     But how the devil could a dumb rock accelerate that fast? Or even at all? Coyote sure as hell would have noticed if someone had landed on RA45 and rigged it for acceleration. The fusion engines required would have been twice the size of her hab shelter. Even if it had happened under her local horizon, it would have been a massive engineering job and she would have felt the vibration of the work rattling RA45. But even the high-end miners who routinely maneuvered their rocks into more convenient orbits never got their boost up over one or two percent of a gee (one-fiftieth-gee). Asteroids were just too massive to make any better headway than that. Even then, the vibration was nearly enough to shake the rock apart.

     Except this baby was cooking along at about three times that velocity without so much as a quiver. She hung in the restraint straps, staring at the range gun’s tiny control panel, utterly baffled. And starting to get very scared. This was a budget hab shelter. It had no radio powerful enough to call for help. No escape pod, either. And without a ship, she had no way off this rock.

     Up until a few days ago, space had made sense. She had known the rules. She was a rock miner. She tracked down smaller asteroids, rocks too small to interest the big-time boys. She bored through the rocks, refined whatever metals and volatiles she could find on the spot, and hauled her refined goods back to make a sale. She had some fun on Ceres or one of the big habs, and then back out again. It was a stable, understandable life.

     The world surrounding her was equally understandable. The asteroids moved in predictable patterns, and she knew how to keep her ship ticking, knew she would die if she got it wrong, knew how to play a dicker with the traders. It was simple.

     She had worked as well as she could with the limited hardware aboard the tank — as she now thought of the hab shelter. She spent her days at the bottom of a cylinder five meters across and fifteen meters high, and was determined at least to make her situation as tolerable as she could. She had gotten her bunk off the ceiling and put it on the floor. She’d rigged lines and ropes so she could climb up to the control panel, and had reset all the restraints and handholds to allow her to move more easily.

     The trickiest job was reprogramming the hab’s tiny position-reporter computer to provide her with tracking data. She felt a real need to keep at least a rough track of where the hell she was going. If she was doing her crude astrogation right, and assuming a constant acceleration and turnaround halfway there, RA45 was headed straight for Mars. She still had not the faintest idea as to why this was happening. Who was doing this? Toward what goal? And how? She had rigged her exterior-view camera on the longest cable she could manage and spooled the cable out far enough for the camera to give her a view of the asteroid’s aft end, trying to get a look at the engines that were doing this. But there were no engines, there was nothing at all back there. Just more rock. Damn it, something was accelerating this rock. If the something wasn’t outside the rock, it had to be inside the asteroid, somehow. But then how was the acceleration even happening? A rocket inside the rock couldn’t work. That meant a reactionless drive.

     Enough of the anything-for-a-buck Las Vegas Free-state tradition had stuck with her that it occurred to her, even in her current predicament, that a reactionless drive ought to be worth something.

     That, and the risk of madness by boredom, were enough to set her to work trying to solve the puzzle. She took her first crack at it by sitting and thinking. This drive seemed to have some attributes of a rocket, and some attributes of a gravity field. Like a rocket, it obviously could be started and presumably stopped at will. Like gravity, it worked without throwing mass in one direction to move in another.

     But gravity couldn’t be pointed in one direction — it radiated out spherically from the center of a mass.

     But if the whole rock were simply falling forward under the influence of some sort of external gravity field, her body would have been pulled along by the gee field precisely as much as the asteroid itself. The relative acceleration between herself and the asteroid would be exactly zero — in other words, she should have been in free-fall, effectively in zero gee. But she was in a very definite five-percent field. Or was it five? That was still just a guess. There had to be a way to measure it.

     What was accelerating her? A magic rocket that didn’t need propellant or fuel or nozzles, or magic gravity you could point in any direction?

     She sat there on the bottom of her tank and worried at the puzzle, perfectly aware of what she was really doing: struggling to keep her mind off another little problem. No matter how the propulsion system worked, she was going to be in a hell of a mess when this rock piled into Mars.

     How did it go? Coyote Westlake tried to remember the lessons from her old pilot’s physics course text on the differences between rockets and gravity.

     No matter where in the system you measure, a rocket-propelled system shows acceleration in the same direction and at the same strength. Not so with gravity. Gravity pulls in from all directions, radially, toward a central point. The further you get from the source, the weaker it gets. So measurements at different points inside a gravity field should reveal different values for both direction and strength of acceleration.

     That clear in her mind, Coyote set to work experimenting. She dropped weights from the ceiling and timed the fall to measure rate of acceleration. She hung other weights on lines to measure direction. Crude stuff, but the answers they gave were damn confusing. Things dropped from the side of the cylinder furthest from the asteroid fell at virtually the same speed as things dropped from closer in, but nothing dropped in a straight line. Everything curved in toward the asteroid as it fell, and curved more sharply when dropped on the rockward side of the shed.

     Weighted cords did not hang straight up and down the way plumb lines were meant to. Instead, they curved throughout their lengths in strange, disturbing patterns, as if they were drawing the gee-field lines of force in midair. It was as if she were in a cross-breed field, somewhere between linear acceleration and a gravity field.

     Directionalized gravity. Suppose someone, somehow, had put a gravity source — a powerful one — just in front of the asteroid, and then set the gee source moving, accelerating? And suppose that someone focused the gee source’s gravity field, somehow, so its entire force was directed through the body of the asteroid, and with just a little of it slopping over to pass through her hab shelter, for example. Think of it as a tractor beam, she told herself. The asteroid would be set to falling, pulled toward the moving gee source, and her hab shelter, outside the path of the beam but physically attached to the asteroid, would experience forward linear acceleration as it was dragged along, with the result that things inside the shed would fall backwards. Plus a little leakage from the tractor beam, pulling in toward the rock. It fits the facts of her situation. Maybe it was even true. That ancient and mythical patron of engineers, Saint Ruben of Goldberg, would have loved it.

     The whole theory depended, however, on there being something to provide a gravity field just ahead of the asteroid. And her exterior camera revealed that there was nothing there.

     Okay then. Run through the facts. There was no rocket pushing the asteroid from behind. And nothing visible to produce the tractor beam that seemed to be pulling it from in front. What did that leave?

     How about something inside the rock, some projector or gadget that produced and accelerated the focused gravity field that seemed to be pulling the asteroid along? A gizmo that in effect pulled the asteroid along by its own bootstraps.

From THE RING OF CHARON by Roger MacBride Allen (1990)

(ed note: this is pretty much pure unmitigated technobable)

     “We tried throwing the planet into Sirius. They merely left the planet hurriedly as it fell toward the star, and broke free from our attractive ray.”
     ...Taj Lamor had some of his men bring an attractive ray projector to the ship. The apparatus turned out to be nearly a thousand tons in weight, and some twenty feet long, ten feet wide and approximately twelve feet high. It was impossible to load the huge machine into the Ancient Mariner, so an examination was conducted on the spot, with instruments whose reading was intelligible to the terrestrians operating it. Its principal fault lay in the fact that, despite the enormous energy of matter given out, the machine still gobbled up such titanic amounts of energy before the attraction could be established, that a very large machine was needed. The ray, so long as maintained, used no more power than was actually expended in moving the planet or other body. The power used while the ray was in action corresponded to the work done, but a tremendous power was needed to establish it, and this power could never be recovered.
     Further, no reaction was produced in the machine, no matter what body it was turned upon. In swinging a planet then, a spaceship could be used as the base for the reaction was not exerted on the machine.
     ...“As I see it, the ray is actually a directed gravitational field. Now here is one thing that makes it more interesting, and more useful. It seems to defy the laws of mechanics. It acts, but there is no apparent reaction! A small ship can swing a world! Remember, the field that generates the attraction is an integral, interwoven part of the mesh of Space. It is created by something outside of itself. Like the artificial matter, it exists there, and there alone. There is reaction on that attractive field, but it is created in Space at that given point, and the reaction is taken by all Space. No wonder it won’t move.
     “The work considerations are fairly obvious. The field is built up. That takes energy. The beam is focused on a body, the body falls nearer, and immediately absorbs the energy in acquiring a velocity. The machine replenishes the energy, because it is set to maintain a certain energy-level in the field. Therefore the machine must do the work of moving the ship, just as though it were a driving apparatus. After the beam has done what is wanted, it may be shut off, and the energy in the field is now available for any work needed. It may be drained back into power coils such as ours for instance, or one might just spend that last iota of power on the job.
     “As a driving device it might be set to pull the entire ship along, and still not have any acceleration detectable to the occupants.
     ...“But how is it that the machine is not moved when exerting such force on some other body?” he asked at last.
     “Oh, the ray concentrates the gravitational force, and projects it. The actual strain is in space. It is space that takes the strain, but in normal cases, unless the masses are very large, no considerable acceleration is produced over any great distance. That law operates in the case of the pulled body; it pulls the gravitational field as a normal field, the inverse-square law applying.
     “But on the other hand, the gravity-beam pulls with a constant force.
     “It might be likened to the light-pressure effects of a spot light and a star. The spotlight would push the sun with a force that was constant, no matter what the distance, while the light pressure of the sun would vary as the inverse square of the distance.
     “But remember, it is not a body that pulls another body, but a gravitational field that pulls another. The field is in space. A normal field is necessarily attached to the matter that it represents, or that represents it as you prefer, but this artificial field has no connection in the form of matter. It is a product of a machine, and exists only as a strain in space. To move it you must move all space, since it, like artificial matter, exists only where it is created in space.
     “Do you see now why the law of action and reaction is apparently flouted? Actually the reaction is taken up by space.”

From INVADERS FROM THE INFINITE by John W. Campbell jr. (1961)

McAndrews Balanced Drive

This was invented by Charles Sheffield, a scientist who was a science fiction author on the side. His "Balanced Drive" is not precisely a carrot-on-a-stick drive. Which is a good thing, since it means this drive can actually work. The bad news is it is unobtainium. The laws of physics do not forbid it, we can calculate its performance, but actually building the monster is way beyond the state-of-the art.

As you recall the advantage of a carrot-on-a-stick is to allow huge acceleration with your spacecraft without killing the crew. The idea is to accelerate the ship at huge levels, but subject the habitat module to an opposed gravitational force in order to counteract the harmful acceleration effects. Sounds simple but as always the devil is in the detail.

The spine of the ship is the "stick." It is 250 meters long and 4 meters in diameter. The combined hab and payload module is threaded on the spine. The module can move along the spine.

The "carrot" part is where the fun begins. It is a disk one hundred meters in diameter and one meter thick. It is composed of electromagnetically stablized compressed matter, with a whopping density of 1,170 tons per cubic centimeter. Less dense than a neutron star, but only just. Mass of the disk is about 9.2×1012 tons, a bit over the mass of Mount Everest.

If you were sitting right in the center of the disk you'd experience exactly 50 gees of gravity and would quickly die. If you were 246 meters away from the disk you'd experience exactly one gee of gravity, due to the distance. This is why the spine is 250 meters long.

The point is: by moving the hab module along the spine, you can alter the gravity it experiences from the disk over a range of 1 to 50 gees.

The ship uses a disk instead of a sphere in order to make the lines of gravitation approximately parallel to the spine, instead of converging to the center of the dense sphere. The tidal forces are about one gee per meter, which isn't much of a problem.

Finally, on the rim of the gravity disk you mount unreasonably strong rocket engines that are powered by a virtually infinite power source. Something that can accelerate a disk of solid neutronium with a mass of Mount Everest at 50 gees for months at a time.

The arrangement is the disk at the top with the rockets firing downward (on the rim so the exhaust does not vaporize the hab module), the spine in the middle, and the hab module at the bottom.

So say you want to crank up the ship so it is accelerating at 32 gees. About the level that will break the crew's bones in five minutes. The rocket engines are gradually throttled up to 32 gees. The crew experiences a rocket acceleration of 32 gees downward, because the rockets accelerate the gravity disk, which tugs on the spine, which tugs on the hab module.

Meanwhile the hab module is moved so it is about 20 meters from the gravity disk. There the crew experiences a gravitational acceleration of 33 gees upward. So 32 gees of rocket acceleration downward plus 33 gees of gravitational acceleration upwards means the crew feels a comfy one gee upward. This is why it is called the "balanced drive."

Naturally you'll need some kind of fail-safe to rapidly move the hab module if the engines fail. The gravity disk can kill you with acceleration just as easily as the rocket engines.


      When the ship was explained to me, I decided that McAndrew didn't really see round corners when he thought. It was just that things were obvious to him before they were explained, and obvious to other people afterwards. I had been saying "inertia-less" to Mac, and he had been just as often saying "impossible." But we hadn't been communicating very well. All I wanted was a drive that would let us accelerate at multiple gees without flattening the passengers. To McAndrew, that was a simple requirement, one that he could easily satisfy—but there was no question of doing away with inertia, of passengers or ship.
     "Take it back to basics," said Wenig, when he was showing me how the Dotterel worked. "Remember the equivalence principle? That's at the heart of it. There is no way of distinguishing an accelerated motion from a gravitational field force, right?"
     I had no trouble with that. It was freshman physics. "Sure. You'd be flattened just as well in a really high gravity field as you would in a ship accelerating at fifty gee. But where does it get you?"
     "Imagine that you were standing on something with a hefty gravity field—Jupiter, say. You'd experience a downward force of about two and a half gee. Now suppose that somebody could accelerate Jupiter away from you, downwards, at two and a half gee. You'd fall towards it, but you'd never reach it—it would be accelerating at the same rate as you are. And you'd feel as though you were in free fall, but so far as the rest of the Universe is concerned you'd be accelerating at two and a half gee, same as Jupiter. That's what the equivalence principle is telling us, that acceleration and gravity can cancel out, if they're set up to be equal and opposite."
     As soon as you got used to Wenig's accent, he was easy to follow—I doubt if anybody could get into the Institute unless he was more than bright enough to explain concepts in easy terms.
     I nodded. "I can understand that easily enough. But you've just replaced one problem with a worse one. You can't find any drive in the Universe that could accelerate Jupiter at two and a half gee."
     "We cannot—not yet, at any rate. Luckily, we don't need to use Jupiter. We can do it with something a lot smaller, and a lot closer. Let's look at the Dotterel and the Merganser. At McAndrew's request I designed the mass element for both of them."
     He went across to the window that looked out from the inside of the Institute to raw space. The Dotterel was floating about ten kilometers away, close enough to see the main components.
     "See the plate on the bottom? It's a hundred meter diameter disk of compressed matter, electromagnetically stabilized and one meter thick. Density's about eleven hundred and seventy tons per cubic centimeter—pretty high, but nothing near as high as we've worked with here at the Institute. Less than you get in anything but the top couple of centimeters of a neutron star, and nowhere near approaching kernel densities. Now, if you were sitting right at the center of that disk, you'd experience a gravitational acceleration of fifty gee pulling you down to the disk. Tidal forces on you would be one gee per meter—not enough to trouble you. If you stayed on the axis of the disk, and moved away from it, you'd feel an attractive force of one gee when you were two hundred and forty-six meters from the center of the disk. See the column growing out from the disk? It's four meters across and two hundred and fifty meters long."
     I looked at it through the scope. The long central spike seemed to be completely featureless, a slim column of grey metal.
     "What's inside it?"
     "Mostly nothing." Wenig picked up a model of the Dotterel and cracked it open lengthwise, so that I could see the interior structure. "When the drives are off, the living-capsule is out here at the far end, two hundred and fifty meters from the dense disk. Gravity feels like one gee, toward the center of the disk. See the drives here, on the disk itself? They accelerate the whole thing away from the center column, so the disk stays flat and perpendicular to the motion. The bigger the acceleration that the drives produce, the closer to the disk we move the living-capsule up the central column here. We keep it so the total force in the capsule, gravity less acceleration, is always one gee, toward the disk."
     He slid the capsule along an electromechanical ladder closer to the disk. "It's easy to compute the right distance for any acceleration—the computer has it built-in, but you could do it by hand in a few minutes. When the drives are accelerating the whole thing at fourteen gee, the capsule is held a little less than fifty meters from the disk. I've been on a test run in the Merganser where we got up to almost twenty gee. Professor McAndrew intended to take it up to higher accelerations on this test. To accelerate at thirty-two gee, the capsule must be about twenty meters from the disk to keep effective gravity inside to one gee. The plan was to take the system all the way up to design maximum—fifty gee thrust acceleration, so that the passengers in the capsule would be right up against the disk, and feel as though they were in free fall. Gravity and thrust accelerations will exactly balance."
     I was getting goose bumps along the back of my neck. I knew the performance of the uncrewed med ships. They would zip you from inside the orbit of Mercury out to Pluto in a couple of days, standing start to standing finish. Once in a while you'd get a passenger on them—accident or suicide. The flattened thing that they unpacked at the other end showed what the human body thought of a hundred gee.
     "What would happen if the drives went off suddenly?" I said.
     "You mean when the capsule is up against the disk—at maximum thrust?" Wenig shook his head. "We designed a safeguard system to prevent that, even on the prototypes. If there were a sign of the drive cutting off, the capsule would be moved back up the column, away from the disk. The system for that is built-in."

     The Dotterel worked like a dream. At twenty gee acceleration relative to the Solar System, we didn't feel anything unusual at all. The disk pulled us towards it at twenty-one gee, the acceleration of the ship pulled us away from it at twenty gee, and we sat there in the middle at a snug and comfortable standard gravity. I couldn't even feel the tidal forces, though I knew they were there.

From MOMENT OF INERTIA by Charles Sheffield (1980)

Negative Matter Drive

The late Dr. Robert L. Forward was a real physicist whose life's work was gravity research. He invented the Forward Mass Detector and had 18 patents to his name, including the Statite. He was the science fiction writer's friend, writing fiction himself and producting research on juicy SF projects like time travel, negative matter, antimatter rockets, and interstellar laser sail starships.

This means all of his material is not science fiction. It is real. Unlike the carrot-on-a-stick drive, it will actually work. Which is disconcerting because the blasted thing is a reactionless drive, with all that implies. Including Burnside's Advice and your science fiction universe dealing with the implications of dirt-cheap planet-wrecking weapons.

His most accessable book on these topics is the collection of science essays Indistinguishable from Magic.

Given his life's work, he does have a few things to say on the topic of gravity.

This is not precisely a "carrot-on-a-stick" drive, but it does have a lot of similarities.

Safety tip: since it is possible to create a chunk of negative matter along with an equal mass of normal matter with no energy, the implication is that a piece of negative matter making contact with normal matter will result in both pieces annihilating each other. Unlike matter making contact with antimatter, no energy is released since no energy was needed to make them. The two chunks will dissolve each other until one or the other is consumed.


(ed note: This is not science fiction, it is reality)

Negative Matter

As unbelievable as these machines for controlling gravity might seem, they at least use a form of matter which we know exists, even if it is presently found only in the interiors of far distant stars. There are speculations that there might exist another type of matter. It has very strange properties. If it ever could be found or made, then a whole new era of gravity control would open up.

All the matter that we know of is the type called regular (positive) matter. Yet both the Newton and the Einstein Theories of Gravity allow the existence of an opposite form of matter, called negative matter. According to the theories of gravity and mechanics, an atom of negative matter would repel all other matter (including other atoms of negative matter).

Now, the first thing you should realize is that negative matter is not "antimatter". Antimatter is different from regular matter in its quantum mechanical properties, not its gravitational properties. Although it has yet to be proven experimentally, we are fairly sure that antimatter attracts other forms of matter, just like normal matter. Negative matter, however, would repel other forms of matter.

We do not know how to make negative matter. But when we do, we will discover that it will not cost us any energy to make that negative matter. Because the rest mass energy of a particle is proportional to its mass (E=mc2), the rest mass energy of a negative mass particle is negative! That means that if we always create equal amounts of positive and negative matter at the same time, it will cost us no net energy to do so! One can imagine a future scene in some huge laboratory, where great machines apply intense electric, magnetic, and gravitational forces to some microscopic point in empty space. The energy levels of the fields are raised higher and higher until the "nothing" itself is ripped apart into a ball of regular matter and an equal sized ball of negative matter, the whole process using no net energy except for the losses in the generating machines.

Once we have our negative matter, we can start using it to make antigravity machines. But we must be very careful how we handle the negative matter. Unlike a chunk of regular matter, which responds to your push by moving away, if you push on a chunk of negative mater, it will come toward you! (If by mistake, you pushed on some negative matter, and it started to move toward you, you must quickly run around behind it and give it a slap on the rear to bring it to a halt!)

Now that we have learned how to control our working material, the simplest antigravity machine that we can make is to form the negative matter into a dense disc and lay it on a good strong floor. If the disc is dense enough and thick enough, then the repulsive gravity field on both sides of the disc will be one Earth gravity. That negative gravity field from the disc would then cancel the gravity field of the Earth. In the region above the disc, the gravity attraction would be zero and you could float there in free fall. (and in a space ship in free fall, such a disc in the ceiling would provide Terra normal gravity by repelling you downward)

The negative gravitational field of negative matter can also be used for gravity propulsion. If you place a ball of very dense negative matter near a similar dense ball of regular matter (which is incidentally attached to your spaceship), you will find that the negative matter ball will repel the regular matter ball, which in turn will attract the negative matter ball. The two dense balls will start to move off in a straight line at a constantly increasing speed. The acceleration will be the strength of the gravitational attraction of one ball for the other, with the negative matter ball chasing after the positive matter ball and the positive matter ball carrying your spaceship along with it. (Question: how do you stop this when you've reached your destination?)

You might at first worry that I'm getting something for nothing. First there were two balls of matter, both standing still, with no kinetic energy. Then, after a while they are both moving off together at high speed with no propulsion energy being expended. You might think that would prove that negative matter is impossible, since it looks like the law of conservation of energy is being violated.

But if you look very closely, you will find that negative mass propulsion does not violate any laws of physics. It is true that the ball of regular mass gains speed and increases its kinetic energy [E=1/2(+m)v2], so it looks like it is getting energy out of nowhere. But while it is doing so, the ball of negative matter is gaining negative energy [E=1/2(-m)v2] and the total energy of the two masses is zero, just as it was when they were standing still. Thus, negative mass propulsion does not violate the law of conservation of energy.

By the same type of argument, you can also show that negative mass propulsion does not violate that other important law of physics, the law of conservation of momentum. For while the momentum of the positive ball of mass is increasing, the momentum of the negative ball of mass is decreasing, resulting in zero net momentum, even though the two balls started out standing still and now are moving off at high speeds.

So far as we know, negative matter doesn't exist. We don't know why it doesn't. After all, both the positive and negative forms of electricity exist, so why not the positive and negative forms of mass? Perhaps there is some yet unknown law of physics that prevents it from forming. But even if we can never obtain this indistinguishable from magic material, we can still devise ways to control gravity with just regular matter, if just work hard and use enough energy and intelligence.

From INDISTINGUISHABLE FROM MAGIC by Robert Forward (1995)

(ed note: Randy's asteroid prospectors discovered an alien creature, which they named the Silverhair. It is apparently composed of negative matter. And so it the "ball", which is basically Silverhair poop.)

     “ After I gave him all the facts and showed him some video segments, he conceded that maybe negative matter could exist after all. What really convinced him was the description of my injury, where the cut edges looked like a thin sliver of material had been evaporated.”
     “Why is that?” asked Randy.
     “Well, as Steve explains it, according to one theory, when negative matter touches normal matter, equal amounts vanish—nothing is left, not even energy. The process is called nullification. It’s like the annihilation of matter by antimatter, but in the nullification process, since the normal matter has positive rest mass and the negmatter has negative rest mass, the net rest mass is zero, so zero energy is released. That’s why we didn’t notice any radiation when the Silverhair and I collided.”
     “What else did Steve have to say?” asked Randy.
     “He told us to look for electric or magnetic fields around the Silverhair and the ball,” said Jim. “Negative-matter particles repel each other gravitationally, so they would normally tend to spread far apart from each other. But since the negative-matter particles in the Silverhair and the ball are jammed together at high density, there must be some other force field involved that holds them together.”
     Philippe spoke up. “Hiroshi found a very strong positive electric field associated with both the ball and the Silverhair. It’s as if the material were all made of particles with the same charge.”
     “Normally, particles of the same charge would repel each other and be pushed apart,” said Jim. “But according to Steve, when you attempt to repel a negative-matter particle, it responds in a perverse manner and comes toward you.”
     “That explains one thing,” said Randy. “Siritha noticed some static-cling effects of space dust on her helmet. But there was nothing large—no lightning bolts.”
     “Both the Silverhair and the ball rapidly develop a cloud of orbiting electrons around them,” said Philippe. “They must attract the negative electrons from the plasma in space while repelling the positive ions. The negative electric charge of the electron cloud cancels out the positive electric charge of the negative matter, unless, of course, you get inside the orbiting cloud of electrons and very close to the surface of the negative matter. Hiroshi got some good measurements of the electric field around the ball by enclosing it in a plastic container, sweeping up all the electrons near the ball with a grounded metallic plate, then making measurements inside the container while all the interfering electrons were forced to stay outside the container. We then did some experiments on the ball.”
     “What kind of experiments?” asked Randy, looking intently at Philippe.
     “Since the ball is charged,” Philippe answered, “it’s easy to push it by charging up a metal plate placed near it. Of course, being negative matter, when you push it, it comes toward you.”
     “That can get dangerous, said Jim, holding up his cast. “If it gets too close, you get nullified.”
     “In the experiment Hiroshi did,” Philippe went on, “he used a metal plate with a negative electric charge so it would attract the positive electric charge of the ball. The ball pulled away in the opposite direction, pulling the test apparatus, the power supply, and Hiroshi along with it. When Hiroshi saw what was happening, he quickly turned the field off. He then had to reverse the field and push on the ball for a while to bring it to a halt again.”
     “It was just as Steve predicted,” said Jim in awe. “A true reactionless space drive.”
     “A space drive?” exclaimed Randy in amazement.
     “That is correct,” said Philippe, his voice deepening as his face turned deadly serious. “When that ball of negative matter was pulling Hiroshi and his test apparatus along, there was nothing going in the opposite direction. There was no reaction mass and no energy source involved, but they moved nevertheless. That means a large enough negative-matter ball electrostatically coupled to a positive-matter spacecraft can propel the spacecraft at any acceleration the crew can stand for as long as you want. Flight to the stars at near light speed is no longer a dream . . .”
     When the enormity of the finding hit Randy, a broad smile spread across his face. An interstellar space drive! He had dreamed of exploring the stars and now his dream, could come true! He leaned forward over the table, eyes on Philippe.
     “What are the limitations?” he asked, knowing there must be some.
     “The mass of the negative matter must be exactly equal and opposite to the positive mass of the spacecraft,” said Philippe. “If it isn’t, then the separation distance between the mass and the spacecraft will change with time. If it gets too close, you risk nullification. If it gets too far away, you risk losing it.
     “You have to control the mass of one or the other, then,” mused Randy. “Not easy.” He thought some more. “Didn’t you say the silver ball has a mass of ten tons?”
     “Yes,” said Philippe. “A negative ten tons.”
     “Then that one ball can drive a ten-ton spacecraft. Do you think you could arrange for a demonstration using one of the prospector flitters? They mass around ten tons.”
     “Perhaps,” said Philippe, thinking. His finger rose to feel the mustache under his nose, then followed it across his face and up over his ear as he thought further about the idea. “Yes,” he said finally.
     “Do it!” said Randy. “I’m going to get some breakfast and then go hack out to see the Silverhair. I wonder if Bob can get it to lay more of those silver eggs.”
     “Careful,” warned Philippe. “Don’t kill the goose ...”

(ed note: since the "eggs" are Silverhair poop, Randy now has access to a steady supply of negative matter)

     A week later, Philippe took Randy to the hangar cavity on the other side of Hygiea.
     “We’ve installed the negmatter drive in the hold,” said Philippe, leading the way as he and Randy floated in through the cargo, door in their space suits. “Right at the center-of-mass of the ship.”
     In the center of the cargo bay was a large, cubical metal box nearly twice as tall as Randy. Surrounding the box were some large power supplies. A technician was tying up some stray wires.
     “Is the negmatter ball in there?” asked Randy.
     “Ready to go,” said Philippe. “All six high-voltage supplies are operating and pushing on the ball equally from all directions. In the control room is a three-axis maglev joyball just like the ones that are used in the drop capsules on the rotovators. You push the ball forward, the fore and aft power supplies change their voltages, the negmatter ball gets pushed in the backward direction, and it responds by moving in the forward direction, pushing the spacecraft ahead of it. If you want to go sideways or vertically, just move the ball in that direction and the power supplies for those axes will respond.”

     “Don’t want to get out of sight of the base,” said Randy, he pulled the joyball to one side to bring them around in a large circle.
     “We’re going sideways!” he complained.
     “With only one ball of negmatter, I was unable to obtain any torque control,” said Hiroshi.
     “l’ll fix that,” said Bob, firing some attitude rockets and tuming the ship around so that it faced in the direction it was traveling. “You just do what you want with the drive controls; boy-boss, and granddaddy Bob will follow your every move and keep us lined up with the straight and narrow.”
     After Randy and Bob had completed a few more practice turns, a warning chime carne from the engineering console in front of Hiroshi. Randy instinctively pulled back on the joyball until they were once again in free-fall.
     “ls there a problem?” he asked apprehensively.
     “The ball of negative matter is starting to drift away from the center of the drive control box,” reported Hiroshi. “As Bob uses fuel to control our orientation, the mass of the spacecraft slowly decreases.”
     “Too bad we can’t control the mass of the ship” said Randy.
     “There is a way to do that,” said Hiroshi. “But I didn’t include that feature in this first design.”
     “In that case,” said Randy, pushing forward on the controls again, “let’s head for base and rework the drive. I want to go back to Earth in style!”

     “Hiroshi’s new six-degree-of-freedom negmatter drive is pretty complicated,” said Philippe. “It has linear drive and torque control in all three axes. For control of the ship’s mass, the hull is covered with activated metal foam that absorbs and holds on to any gas or dust that strikes it. With a constant flow of positive matter coming in, we can afford to shoot propellant out from ion engines to provide mass trim and drag makeup.
     “lt’s amazing how fast Hiroshi and the rest of your techs solved the engineering problems of coping with negmatter,” said Randy.
     “Since the negmatter is electrically charged, it turned out to be easy,” said Philippe. “You use radio fields to make the balls vibrate. If you vibrate them at just the right frequency, you can make them break into two, three, or four pieces, or even spit out little droplets.”
     “Glop those small pieces together and you can make any-sized ball you want,” said Randy. “I still think it’s amazing. ”...
     “You sure are a lucky bastard, Randy,” started Steve. “One little find, and you end up owning a spacewarp, a reactionless space drive, and a nearly infinite source of free energy.”
     “Free energy?” Randy repeated, a little taken aback.
     “Yep,” said Steve. “When negative matter and positive matter interact through long-distance forces, the negative matter gains negative kinetic energy, while the positive matter gains positive kinetic energy. Take a drop of highly charged negative matter, push on it with electric fields until it is going at nearly the speed of light, and in return you get electrical energy back. The only limit on the amount of energy you can get is how close to the speed of light you can push the negative matter before losing control of it.”
     “That could cause a serious hazard,” said Randy. “The whole solar system contaminated with high-speed negative-matter particles.”
     “Simple solution,” replied Steve. “Just direct the high-speed negative matter into a beam stop. Generic dirt will do. The negmatter with all its negative kinetic energy will just disappear when it hits the dirt and nullifies.”
     “Hmmm,” said Randy. “Looks like I had better start an energy production division.”

(ed note: and you know that eventually somebody is going to weaponize this. Disintegrator ray or what?)

From TIMEMASTER by Robert Forward (1992)

(ed note: the dreaded negaspheres and negabombs from E. E. "Doc" Smith's LENSMAN series are apparently antimatter, but in some respects they act like negative matter)

      This was sheerest exaggeration, of course, for nothing could have kept the Lensman from watching the construction of that first apparatus. He watched the erection of a spherical shell of loosely latticed truss-work some twenty feet in diameter. He watched the installation, at its six cardinal points, of atomic exciters, each capable of transforming ten thousand pounds per hour of substance into pure energy. He knew that those exciters were driving their intake screens at a ratio of at least twenty thousand to one; that energy equivalent to the annihilation of at least six hundred thousand tons per hour of material was being hurled into the center of that web from the six small mechanisms which were in fact super-Bergenholms. Nor is that word adequate to describe them; their fabrication would have been utterly impossible without Medonian conductors and insulation.
     "But I want to see it work, you big lug!" Kinnison retorted, only half playfully.
     "Come back in three-four days—maybe a week; but don't expect to see anything but a hole."
     "That's exactly what I want to see, a hole in space," and that was precisely what, a few days later, the Lensman did see.
     The spherical framework was unchanged, the machines were still carrying easily their incredible working load. Material—any and all kinds of stuff—was still disappearing; instantaneously, invisibly, quietly, with no flash or fury to mark its passing.
     But at the center of that massive sphere there now hung poised a… a something. Or was it a nothing? Mathematically, it was a sphere, or rather a negasphere, about the size of a baseball; but the eye, while it could see something, could not perceive it analytically.
     Nor could the mind envision it in three dimensions, for it was not essentially three-dimensional in nature. Light sank into the thing, whatever it was, and vanished. The peering eye could see nothing whatever of shape or of texture; the mind behind the eye reeled away before infinite vistas of nothingness.

     The master technician had cut his controls and every pound of metal and other substance surrounding the negasphere had fallen into that enigmatic realm of nothingness. No connection or contact with it was now possible; and with its carefully established intrinsic velocity it rushed engulfingly toward the doomed planet One of the mastodonic fortresses, lying in its path, vanished utterly, with nothing save a burst of invisible cosmics to mark its passing. It approached its goal. It was almost upon it before any of the defenders perceived it, and even then they could neither understand nor grasp it. All detectors and other warning devices remained static, but…
     Gigantic pressors shoved against it: beams of power sufficient to deflect a satellite; beams whose projectors were braced, in steel-laced concrete down to bedrock, against any conceivable thrust. But this was negative, not positive matter—matter negative in every respect of mass, inertia, and force. To it a push was a pull. Pressors to it were tractors—at contact they pulled themselves up off their massive foundations and hurtled into the appalling blackness.
     Then the negasphere struck. Or did it? Can nothing strike anything? It would be better, perhaps, to say that the spherical hyper-plane which was the three-dimensional cross-section of the negasphere began to occupy the same volume of space as that in which Jalte's unfortunate world already was. And at the surface of contact of the two the materials of both disappeared.
     The substance of the planet vanished, the incomprehensible nothingness of the negasphere faded away into the ordinary vacuity of empty space.
     Jalte's base, the whole three hundred square miles of it, was taken at the first gulp. A vast pit opened where it had been, a hole which deepened and widened with horrifying rapidity. And as the yawning abyss enlarged itself the stuff of the planet fell into it, in turn to vanish.
     Mountains tumbled into it, oceans dumped themselves into it. The hot, frightfully compressed and nascent material of the planet's core sought to erupt—but instead of moving, it, too, vanished. Vast areas of the world's surface crust, tens of thousands of square miles in extent, collapsed into it, splitting off along crevasses of appalling depth, and became nothing. The stricken globe shuddered, trembled, ground itself to bits in paroxysm after ghastly paroxysm of disintegration.

GRAY LENSMAN by E. E. "Doc" Smith (1939)

     Haynes assembled Grand Fleet. Then, while the two black speedsters kept unobtrusively on with the task of plotting the line, Civilization's mighty armada moved a few thousand parsecs aside and headed at normal touring blast for the nearest outcropping of the Second Galaxy.
     There was nothing of stealth in this maneuver, nothing of finesse, excepting in the arrangements of the units. First, far in the van, flew the prodigious, irregular cone of scout cruisers. They were comparatively small, not heavily armed or armored, but they were ultra-fast and were provided with the most powerful detectors, spotters, and locators known. They adhered to no rigid formation, but at the will of their individual commanders, under the direct supervision of Grand Fleet Operations in the Z9M9Z, flashed hither and thither ceaselessly—searching, investigating, mapping, reporting.
     Backing them up came the light cruisers and the cruising bombers—a new type, this latter, designed primarily to bore in to close quarters and to hurl bombs of negative matter. Third in order were the heavy defensive cruisers. These ships had been developed specifically for hunting down Boskonian commerce raiders within the galaxy.
     They wore practically impenetrable screen, so that they could lock to and hold even a super-dreadnought. They had never before been used in Grand Fleet formation; but since they were now equipped with tractor zones and bomb-tubes, theoretical strategy found a good use for them in this particular place.
     Next came the real war-head—a solidly packed phalanx of maulers. All the ships up ahead had, although in varying degrees, freedom of motion and of action. The scouts had practically nothing else; fighting was not their business. They could fight, a little, if they had to; but they always ran away if they could, in whatever direction was most expedient at the time. The cruising bombers could either take their fighting or leave it alone, depending upon circumstances—in other words, they fought light cruisers, but ran away from big stuff, stinging as they ran. The heavy cruisers would fight anything short of a mauler, but never in formation: they always broke ranks and fought individual dog-fights, ship to ship.
     But that terrific spear-head of maulers had no freedom of motion whatever.
     If knew only one direction—straight ahead. It would swerve aside for an inert planet, but for nothing smaller; and when it swerved it did so as a whole, not by parts. Its function was to blast through—straight through—any possible opposition, if and when that opposition should have been successful in destroying or dispersing the screens of lesser vessels preceding it. A sunbeam was the only conceivable weapon with which that stolid, power-packed mass of metal could not cope; and, the Patrolmen devoutly hoped, the zwilniks didn't have any sunbeams—yet.
     A similar formation of equally capable maulers, meeting it head-on, could break it up, of course.
     Theoretical results and war-game solutions of this problem did not agree, either with each other or among themselves, and the thing had never been put to the trial of actual battle. Only one thing was certain—when and if that trial did come there was bound to be, as in the case of the fabled meeting of the irresistible force with the immovable object, a lot of very interesting by-products.
     Flanking the maulers, streaming gracefully backward from their massed might in a parabolic cone, were arranged the heavy battleships and the super- dreadnoughts; and directly behind the bulwark of flying fortresses, tucked away inside the protecting envelope of big battle-wagons, floated the Z9M9Z—the brains of the whole outfit.
     There were no free planets, no negaspheres of planetary anti-mass, no sunbeams. Such things were useful either, hi the defense of a Prime Base or for an all-out, ruthlessly destructive attack upon such a base. Those slow, cumbersome, supremely powerful weapons would come later, after the Patrol had selected the planet which they intended to hold against everything the Boskonians could muster. This present expedition had as yet no planet to defend, it sought no planet to destroy. It was the vanguard of Civilization, seeking a suitable foothold hi the Second Galaxy and thoroughly well equipped to argue with any force mobile enough to bar its way.

     And the Patrol's psychologists had had ideas, based upon facts which they had gathered from Kinnison and from Illona and from many spools of tape—ideas by virtue of which it was eminently possible that the conventional light cruisers of Civilization, with their heavier screen and more and hotter beams, could vanquish the light cruisers of the foe, even though they should turn out to be negative-matter bombers.
     Hence the fifty-fifty division of types; but, since Haynes was not thoroughly sold upon either the psychologists or their ideas, the commanders of his standard light cruisers had received very explicit and definite orders. If the Boskonians should have negabombs and if the high-brows' idea did not pan out, they were to turn tail and run, at maximum and without stopping to ask questions or to get additional instructions.
     Haynes had not really believed that the enemy would have negabombs, they were so new and so atrociously difficult to handle. He wanted—but was unable—to believe implicitly in the psychologist's findings. Therefore, as soon as he saw what was happening, he abandoned his tank for a moment to seize a plate and get into full touch with the control room of one of the conventional light cruisers then going into action.
     He watched it drive boldly toward a Boskonian vessel which was in the act of throwing bombs.
     He saw that the agile little vessel's tractor zone was out. He watched the bombs strike that zone and bounce. He watched the tractor-men go to work and he saw the psychologists' idea bear splendid fruit. For what followed was a triumph, not of brute force and striking power, but of morale and manhood. The brain-men bad said, and it was now proved, that the Boskonian gunners, low-class as they were and driven to their tasks like the slaves they were, would hesitate long enough before using tractor- beams as pressors so that the Patrolmen could take their own bombs away from them!
     For negative matter, it must be remembered, is the exact opposite of ordinary matter. To it a pull is, or becomes, a push; the tractor beam which pulls ordinary matter toward its projector actually pushed negative matter away.
     The "boys" of the Patrol knew that fact thoroughly. They knew all about what they were doing, and why. They were there because they wanted to be, as Illona had so astoundingly found out, and they worked with their officers, not because of them. With the Patrol's gun-crews it was a race to see which crew could capture the first bomb and the most.
     Aboard the Boskonian how different it was! There the dumb cattle had been told what to do, but not why. They did not know the fundamental mechanics of the bomb-tubes they operated by rote; did not know that they were essentially tractor-beam projectors. They did know, however, that tractor beams pulled things toward them; and when they were ordered to swing their ordinary tractors upon the bombs which the Patrolmen were so industriously taking away from them, they hesitated for seconds, even under the lash.
     This hesitation was fatal. Haynes' gleeful gunners, staring through their special finders, were very much on their toes; seconds were enough. Their fierce-driven tractors seized the inimical bombs in mid-space, and before the Boskonians could be made to act in the only possible opposition hurled them directly backward against the ships which had issued them. Ordinary defensive screen did not affect them; repulsor screen, meteorite—and wall-shields only sucked them inward the faster.
     And ordinary matter and negative matter cannot exist in contact. In the instant of touching, the two unite and disappear, giving rise to vast quantities of intensely hard radiation. One negabomb was enough to put any cruiser out of action, but here there were usually three or four at once.
     Sometimes as many as ten; enough almost, to consume the total mass of a ship.
     A bomb struck; ate in. Through solid armor it melted. Atmosphere rushed out, to disappear en route—for air is normal matter. Along beams and trusses the hellish hyper-sphere travelled freakishly, although usually in the direction of greatest mass. It clung, greedily. Down stanchions it flowed; leaving nothing in its wake, flooding all circumambient space with lethal emanations.
     Into and through converters. Into pressure tanks, which blew up enthusiastically. Men's bodies it did not seem to favor—not massive enough, perhaps—but even them it did not refuse if offered. A Boskonian, gasping frantically for air which was no longer there and already half mad, went completely mad as he struck savagely at the thing and saw his hand and his arm to the shoulder vanish instantaneously, as though they had never been.

SECOND STAGE LENSMAN by E. E. "Doc" Smith (1941)

From the LENSMAN SERIES by E. E. "Doc" Smith


A new theory brings up the possibility that negative matter actually exists. Which means that Timemaster might be science-fact, not science-fiction.

Astronomers can observe objects like stars and calculate gravitational effects. Then they ran into some serious anomalies. The main one was that the galaxies as observed cannot exist. Their mass can be calculated by counting the stars and nebula. The problem is that there is not enough mass to keep the galaxies from flying apart into individual stars. The secondary problem is sightings of gravitational lenses. Blasted galaxies did not have enough mass to cause the degree of lensing observed.

So there has to be some matter in galaxies that cannot be observed. This was given the unoriginal name of Dark Matter. There is a lot of it, too, about 85% of the matter in the entire universe is dark matter.

Meanwhile there was a totally different anomaly. The universe was created in the Big Bang. Everything in the universe is flying apart from the explosion. Now, the universe might have enough matter with enough gravitational attraction to halt the universe's expansion and cause it to halt and start contracting. Otherwise the expansion will just slow down as time goes by.

Astronomers were nonplussed to discover that the rate of expansion was accelerating. This was impossible.

The cause is unknown, but was given the unoriginal name of Dark Energy just so it could have a label.

There have been many different theories proposed to explain dark matter and dark energy, but none of them have gained enough evidence to survive the scientific method.

Some researchers drew inspiration from Occam's razor. They realized that things would be more Occam-like if dark matter and dark energy were two aspects of the same thing. Then you would have just one mysterious force to deal with, instead of two.

Some tried to explain the anomalies of both spinning galaxies and accelerating expansion by saying it wasn't the matter that was the problem, it was the theory of gravitational motion that was at fault. This Modified Newtonian dynamics family of theories. This was more or less discredited by the observations of the Bullet Cluster. Can't be predicted by MOND, but can be by some kind of weird dark matter.

So the other alternative to getting more Occam into the theory is to postulate that both dark matter and dark energy are two aspects of the same stuff. This is the Dark Fluid theory.

To cut to the chase, dark fluid appears to be Negative Matter.

Dr. Jamie Farnes from the Oxford e-Research Centre has formulated a theory of dark fluid, and one of the requirements is that dark fluid have the properies of negative matter. Just what we need for a negative matter drive.

And to add to the fun, remember that in 1994 physicist Miguel Alcubierre crafted a scientific theory specifically to act like the famous "warp drive" from Star Trek, the Alcubierre drive. It is a pity it cannot be made. Among other things is requires something called "negative matter." Oh, wait!


      Scientists at the University of Oxford may have solved one of the biggest questions in modern physics, with a new paper unifying dark matter and dark energy into a single phenomenon: a fluid which possesses 'negative mass." If you were to push a negative mass, it would accelerate towards you. This astonishing new theory may also prove right a prediction that Einstein made 100 years ago.
     Our current, widely recognised model of the Universe, called LambdaCDM, tells us nothing about what dark matter and dark energy are like physically. We only know about them because of the gravitational effects they have on other, observable matter.
     This new model, published today in Astronomy and Astrophysics, by Dr. Jamie Farnes from the Oxford e-Research Centre, Department of Engineering Science, offers a new explanation. Dr. Farnes says: "We now think that both dark matter and dark energy can be unified into a fluid which possesses a type of 'negative gravity," repelling all other material around them. Although this matter is peculiar to us, it suggests that our cosmos is symmetrical in both positive and negative qualities."
     The existence of negative matter had previously been ruled out as it was thought this material would become less dense as the Universe expands, which runs contrary to our observations that show dark energy does not thin out over time. However, Dr. Farnes' research applies a 'creation tensor," which allows for negative masses to be continuously created. It demonstrates that when more and more negative masses are continually bursting into existence, this negative mass fluid does not dilute during the expansion of the cosmos. In fact, the fluid appears to be identical to dark energy.
     Dr. Farnes's theory also provides the first correct predictions of the behaviour of dark matter halos. Most galaxies are rotating so rapidly they should be tearing themselves apart, which suggests that an invisible 'halo' of dark matter must be holding them together. The new research published today features a computer simulation of the properties of negative mass, which predicts the formation of dark matter halos just like the ones inferred by observations using modern radio telescopes.
     Albert Einstein provided the first hint of the dark universe exactly 100 years ago, when he discovered a parameter in his equations known as the 'cosmological constant," which we now know to be synonymous with dark energy. Einstein famously called the cosmological constant his 'biggest blunder," although modern astrophysical observations prove that it is a real phenomenon. In notes dating back to 1918, Einstein described his cosmological constant, writing that 'a modification of the theory is required such that "empty space" takes the role of gravitating negative masses which are distributed all over the interstellar space." It is therefore possible that Einstein himself predicted a negative-mass-filled universe.
     Dr. Farnes says: "Previous approaches to combining dark energy and dark matter have attempted to modify Einstein's theory of general relativity, which has turned out to be incredibly challenging. This new approach takes two old ideas that are known to be compatible with Einstein's theory—negative masses and matter creation—and combines them together.
     "The outcome seems rather beautiful: dark energy and dark matter can be unified into a single substance, with both effects being simply explainable as positive mass matter surfing on a sea of negative masses."
     Proof of Dr. Farnes's theory will come from tests performed with a cutting-edge radio telescope known as the Square Kilometre Array (SKA), an international endeavour to build the world's largest telescope in which the University of Oxford is collaborating.
     Dr. Farnes adds: "There are still many theoretical issues and computational simulations to work through, and LambdaCDM has a nearly 30 year head start, but I'm looking forward to seeing whether this new extended version of LambdaCDM can accurately match other observational evidence of our cosmology. If real, it would suggest that the missing 95% of the cosmos had an aesthetic solution: we had forgotten to include a simple minus sign."


It’s embarrassing, but astrophysicists are the first to admit it. Our best theoretical model can only explain 5% of the universe. The remaining 95% is famously made up almost entirely of invisible, unknown material dubbed dark energy and dark matter. So even though there are a billion trillion stars in the observable universe, they are actually extremely rare.

The two mysterious dark substances can only be inferred from gravitational effects. Dark matter may be an invisible material, but it exerts a gravitational force on surrounding matter that we can measure. Dark energy is a repulsive force that makes the universe expand at an accelerating rate. The two have always been treated as separate phenomena. But my new study, published in Astronomy and Astrophysics, suggests they may both be part of the same strange concept – a single, unified “dark fluid” of negative masses.

Negative masses are a hypothetical form of matter that would have a type of negative gravity – repelling all other material around them. Unlike familiar positive mass matter, if a negative mass was pushed, it would accelerate towards you rather than away from you.

Negative masses are not a new idea in cosmology. Just like normal matter, negative mass particles would become more spread out as the universe expands – meaning that their repulsive force would become weaker over time. However, studies have shown that the force driving the accelerating expansion of the universe is relentlessly constant. This inconsistency has previously led researchers to abandon this idea. If a dark fluid exists, it should not thin out over time.

In the new study, I propose a modification to Einstein’s theory of general relativity to allow negative masses to not only exist, but to be created continuously. “Matter creation” was already included in an early alternative theory to the Big Bang, known as the Steady State model. The main assumption was that (positive mass) matter was continuously created to replenish material as the universe expands. We now know from observational evidence that this is incorrect. However, that doesn’t mean that negative mass matter can’t be continuously created. I show that this assumed dark fluid is never spread too thinly. Instead it behaves exactly like dark energy.

I also developed a 3D computer model of this hypothetical universe to see if it could also explain the physical nature of dark matter. Dark matter was introduced to explain the fact that galaxies are spinning much faster than our models predict. This implies that some additional invisible matter must be present to prevent them from spinning themselves apart.

My model shows that the surrounding repulsive force from dark fluid can also hold a galaxy together. The gravity from the positive mass galaxy attracts negative masses from all directions, and as the negative mass fluid comes nearer to the galaxy it in turn exerts a stronger repulsive force onto the galaxy that allows it to spin at higher speeds without flying apart. It therefore appears that a simple minus sign may solve one of the longest standing problems in physics.

Is the universe really this weird?

One may argue that this sounds a little far fetched. But while negative masses are bizarre, they are considerably less strange than you may immediately think. For starters, these effects may only seem peculiar and unfamiliar to us, as we reside in a region dominated by positive mass.

Whether physically real or not, negative masses already have a theoretical role in a vast number of areas. Air bubbles in water can be modelled as having a negative mass. Recent laboratory research has also generated particles that behave exactly as they would if they had negative mass.

And physicists are already comfortable with the concept of negative energy density. According to quantum mechanics, empty space is made up of a field of fluctuating background energy that can be negative in places – giving rise to waves and virtual particles that pop into and out of existence. This can even create a tiny force that can be measured in the lab.

The new study could help solve many problems in modern physics. String theory, which is our best hope for unifying the physics of the quantum world with Einstein’s theory of the cosmos, is currently seen as being incompatible with observational evidence. However, string theory does suggest that the energy in empty space must be negative, which corroborates the theoretical expectations for a negative mass dark fluid.

Moreover, the team behind the groundbreaking discovery of an accelerating universe surprisingly detected evidence for a negative mass cosmology, but took the reasonable precaution of interpreting these controversial findings as “unphysical”.

The theory could also solve the problem of measuring the universe’s expansion. This is explained by the Hubble-Lemaître Law, the observation that more distant galaxies are moving away at a faster rate. The relationship between the speed and the distance of a galaxy is set by the “Hubble constant”, but measurements of it have continued to vary. This has led to a crisis in cosmology. Fortunately, a negative mass cosmology mathematically predicts that the Hubble “constant” should vary over time. Clearly, there is evidence that this weird and unconventional new theory deserves our scientific attention.

Where to go from here

The creator of the field of cosmology, Albert Einstein, did – along with other scientists including Stephen Hawking – consider negative masses. In fact, in 1918 Einstein even wrote that his theory of general relativity may have to be modified to include them.

Despite these efforts, a negative mass cosmology could be wrong. The theory seems to provide answers to so many currently open questions that scientists will – quite rightly – be rather suspicious. However, it is often the out-of-the-box ideas that provide answers to longstanding problems. The strong accumulating evidence has now grown to the point that we must consider this unusual possibility.

The largest telescope to ever be built – the Square Kilometre Array (SKA) – will measure the distribution of galaxies throughout the history of the universe. I’m planning to use the SKA to compare its observations to theoretical predictions for both a negative mass cosmology and the standard one – helping to ultimately prove whether negative masses exist in our reality.

What is clear is that this new theory generates a wealth of new questions. So as with all scientific discoveries, the adventure does not end here. In fact, the quest to understand the true nature of this beautiful, unified, and – perhaps polarised – universe has only just begun.


The problem I've always had with negative matter is that if it interacted with anything at all, you would get a runaway instability. Say, for example, that the negative stuff interacted with light. Instead of absorbing light, it would amplify it, leading to an exponential runaway light intensity while simultaneously increasing the temperature of the negative stuff. So bad news.

But — this is "dark" matter and energy. It doesn't interact with anything that we know of (except gravity, which might give us some loopholes). So who knows, maybe it would work.

And it seems like one of those "HA HA YOU CAN'T HAVE IT" moments for us sci fi fans. We get the negative matter needed to make wormholes or warp drives or whatever, but we can't possibly interact with it in any way. Sob.

From Dr. Luke Campbell (2018)

The Altar On Asconel


      No, rational thought was beyond him at the moment. Wait till the drive settled down to free-space operation—that would be soon enough to solve the riddle.
     He (Spartak) was on the point of returning to his cabin when he heard the cry.


     And the drive went off.
     The shock was like a dash of cold water, clearing the fog from his brain. With reflex speed he made for the companionway, scrambling up it with the agility of a Sirian ape.
     The shock was renewed as soon as he saw what was happening in the control room. It was no girl that he had glimpsed passing this way. It was a man, huge and bulky as a Thanis bull, his hair wild, his body cased in crude leather harness and his feet in steel-tipped boots, who now was wrestling chest-to-chest with the tough but far smaller Vix (Spartak's brother), overbearing the redhead in a crushing embrace.
     Vix tried to butt him on the nose, failed as the attacker jerked his head back, lost his balance to one of the steel-tipped boots as it cracked against his ankle, and went slamming down to the floor. He had had no time to draw his sidearms, obviously—perhaps he'd mistaken the sound of the stranger's approach for Spartak's—but he'd done well in the first instance, for a short sword lay at the foot of the control board: his assailant's, logically, which he had somehow contrived to dash from his grip.
     Horrified, Spartak saw the two antagonists crash to their full length, saw the stranger break Vix's grasp on his right wrist and force his hand closer and closer to the redhead's throat. Wild pleading showed in the green eyes, but there was no breath available for him to call for aid again.

     To renounce his oath so soon? (Spartak had taken an oath of non-violence) To pick up the sword from the floor and drive it into the stranger's back? It could be done, but—
     And then he remembered, as clearly as if he were hearing it in present time, the voice of one of his earliest tutors on Annanworld. “Always bear in mind that the need for violence is an illusion. If it seems that violence is unavoidable, what this means is that you've left the problem too late before starting to tackle it."

     Spartak dodged the struggling men and made for the control board. As he scanned the totally unfamiliar switches, he heard a sobbing cry from Vix—“Spartak, Spartak, he's going to strangle me!"
     Time seemed to plod by for him, while racing at top speed for his brother. But at last he thought he had it. He put one hand on the back of the pilot chair, and with the other slammed a switch over past its neutral point to the opposite extreme of its traverse.
     Instantly he went head over heels. But he was prepared for this; in effect, he fell to the ceiling like a gymnast turning a somersault, and landed on his feet with a jar that shook him clear to the hips. The universe rolled insanely around him, and through a swirling mist of giddiness he saw that what he had intended had indeed come about. Locked in their muscle-straining embrace, Vix and the unknown had crashed ten feet to the ceiling as the gravity reversed, and now Vix was on top—and breaking free! For the force of the upside-down fall had completely stunned the stranger.
     Spartak reached out, clutching Vix by the loose baldric on which he normally slung his energy-gun, and reversed the gravity once more, restoring its normal direction. The attacker slammed to the floor again while he and Vix fell rather less awkwardly; this time, he moved the switch with careful slowness, not exceeding a quarter-gravity till he felt his soles touch the floor.

     And then he said, “Who is he?”
     “I—I—" Vix put his hands to his temples and pressed, breathing in enormous sobbing gasps. “What did you do?"
     “I put the gravity over to full negative."
     “But—" Vix began to recover. “But—how? Do you know these ships, then?"
     “No, I've never seen one before. But it followed logically. There's always an automatic gravity compensator on a starship, for high-gee maneuvering in normal space, and it seemed reasonable to expect a manual over-ride on a vessel like this which might get damaged during combat.”
     “You mean you just took a chance on it, while he was throttling the life out of me?" Vix exploded.
     Clearly the redhead had suffered one of the worst frights of his life. Spartak hesitated.

From THE ALTAR ON ASCONEL by John Brunner (1965)

Star Surgeon


By the fourth day the attack showed no signs of diminishing. The rattlers on the outer hull were going almost constantly, their power drain making the lights flicker.

The principle which furnished artificial gravity for the floor and compensated for the killing accelerations used by the ships also lay behind the weapons of both sides — the repulsion screen, originally a meteor protection device, the tractor and pressor beams, and the rattler which was a combination of both. The rattler pushed and pulled — vibrated — depending on how narrowly it was focused, at up to eighty Gs. A push of eighty gravities then a pull of eighty gravities, several times a minute. Naturally it was not always focused accurately on target, both ships were moving and taking counter-measures, but it was still tight enough to tear the plating off a hull or, in the case of a small ship, to shake it until the men inside rattled.

There was no fine diagnostic skill required in the treatment of these rattled men. It was all too plain that they suffered from multiple and complicated fractures, some of them of nearly every bone in their bodies. Many times when he had to cut one of the smashed bodies out of its suit Conway wanted to yell at the men who had brought it in, "What do you expect me to do with this. . ."

But this was alive, and as a doctor he was supposed to do everything possible to make it stay that way.

From STAR SURGEON by James White (1963)

The main screen showed a line of heavy cruisers playing ponderous follow-the-leader along the first section of the incision, rattlers probing deep while their pressers held the edges of the wound apart to allow deeper penetration by the next ship in line. Like all of the Emperor class ships they were capable of delivering a wide variety of frightfulness in very accurately metered doses, from putting a few streets full of rioters to sleep to dispensing atomic annihilation on a continental scale. The Monitor Corps rarely allowed any situation to deteriorate to the point where the use of mass destruction weapons became the only solution, but they kept them as a big and potent stick — like most policemen, the Federation's law-enforcement arm knew that an undrawn baton had better and more long-lasting effects than one that was too busy cracking skulls. But their most effective and versatile close-range weapon — versatile because it served equally well either as a sword or a plowshare — was the rattler.

A development of the artificial gravity system which compensated for the killing accelerations used by Federation spaceships, and of the repulsion screen which gave protection against meteorites or which allowed a vessel with sufficient power reserves to hover above a planetary surface like an old-time dirigible airship, the rattler beam simply pushed and pulled, violently, with a force of up to one hundred Gs, several times a minute.

It was very rarely that the corps were forced to use their rattlers in anger — normally the fire-control officers had to be satisfied with using them to clear and cultivate rough ground for newly established colonies — and for the optimum effect the focus had to be really tight. But even a diffuse beam could be devastating, especially on a small target like a scout ship. Instead of tearing off large sections of hull plating and making metallic mincemeat of the underlying structure, it shook the whole ship until the men inside rattled.

From MAJOR OPERATION by James White (1971)



Among things that you all can be thankful for is that gravitic weapons are of almost no practical use. Partly this is because there is very little training we can give you in dealing with the resulting casualties – due to the low survival rate – but mostly because the results are ugly even by time-of-war standards.

“Gravitic shear, first, ripping a ship in twain with an opposed tractor and pressor, is probably the least bad in damage, but the worst to attend. At least that one might have survivors in the remaining halves, albeit survivors who’ve broken almost every bone in their bodies from the abrupt acceleration, but anything near the shear line will be torn apart. Worst, though, is anyone caught in the fringe effect – that bends and stretches flesh in all the wrong ways. Sophs who’ve been twisted into abstract artwork, and some of them even live through it.

“Then there’s gravitic vibration. ‘Rattling’. Leaves no bodies to bury, because it leaves no bodies. The effects are similar to an inertial damper failure, leaving you with a ship full of meat-slurry. No call for medical treatment; cleaning up after this just needs a hose, a mop, and a well-callused soul.

“And lastly there’s gravitic implosion. There are no slides for this one. No-one, to my knowledge, has ever used a gravitic imploder in combat, but if you insist upon knowing, you can find images of the tests on the IN med-weave. I do not recommend doing so. Spaghettification should have stayed beneath the event horizons where we found it…”

– Surgeon-Commander Vinea Allatrian-ith-Aplan,
lecture at the Faculty of Medicine, Imperial War College

From GRAVY by Alistair Young (2020)

The Songs of Distant Earth

This is from Sir Arthur C. Clarke's original 1958 short story. He later re-wrote it as a novel in 1986, where the starship crew used a more scientifically plausible but much more boring technique to lift the water.

     "I'm not sure," he replied, truthfully enough. "It depends on how long the repairs take."
     "What went wrong?"
     "Oh, we ran into something too big for our meteor screen to absorb. And — bang! — that was the end of the screen. So we've got to make a new one."
     "And you think you can do that here?"
     "We hope so. The main problem will be lifting about a million tons of water up to the Magellan. Luckily, I think Thalassa can spare it."
     "Water? I don't understand."
     "Well, you know that a starship travels at almost the speed of light; even then it takes years to get anywhere, so that we have to go into suspended animation and let the automatic controls run the ship."
     Lora nodded. "Of course — that's how our ancestors got here."
     "Well, the speed would be no problem if space was really empty — but it isn't. A starship sweeps up thousands of atoms of hydrogen, particles of dust, and sometimes larger fragments, every second of its flight. At nearly the speed of light, these bits of cosmic junk have enormous energy, and could soon burn up the ship. So we carry a shield about a mile ahead of us, and let that get burned up instead. Do you have umbrellas on this world?"
     "Why — yes," Lora replied, obviously baffled by the incongruous question.
     "Then you can compare a starship to a man moving head down through a rainstorm behind the cover of an umbrella. The rain is the cosmic dust between the stars, and our ship was unlucky enough to lose its umbrella."
     "And you can make a new one of water?"
     "Yes; it's the cheapest building material in the universe. We freeze it into an iceberg which travels ahead of us. What could be simpler than that?"

     Lora pretended to work, but she typed the same sentence eight times while Leon delivered his message from the captain of the Magellan. She was not a great deal wiser when he had finished; it seemed that the starship's engineers wished to build some equipment on a headland a mile from the village, and wanted to make sure there would be no objection.
     "Of course!" said Mayor Fordyce expansively, in his nothing's-too-good-for-our-guests tone of voice. "Go right ahead — the land doesn't belong to anybody, and no one lives there. What do you want to do with it?"
     "We're building a gravity inverter, and the generator has to be anchored in solid bedrock. It may be a little noisy when it starts to run, but I don't think it will disturb you here in the village. And of course we'll dismantle the equipment when we've finished."

     By the end of the week, the visitors had built a squat and heavily braced pyramid of metal girders, housing some obscure mechanism, on a rocky headland overlooking the sea. Lora, in common with the 571 other inhabitants of Palm Bay and the several thousand sight-seers who had descended upon the village, was watching when the first test was made. No one was allowed to go within a quarter of a mile of the machine — a precaution that aroused a good deal of alarm among the more nervous islanders. Did the Earthmen know what they were doing? Suppose that something went wrong. And what were they doing, anyway?
     Leon was there with his friends inside that metal pyramid, making the final adjustments — the 'coarse focusing', he had told Lora, leaving her none the wiser. She watched with the same anxious incomprehension as all her fellow islanders until the distant figures emerged from the machine and walked to the edge of the flat-topped rock on which it was built. There they stood, a tiny group of figures silhouetted against the ocean, staring out to sea.
     A mile from the shore, something strange was happening to the water. It seemed that a storm was brewing — but a storm that kept within an area only a few hundred yards across. Mountainous waves were building up, smashing against each other and then swiftly subsiding again. Within a few minutes the ripples of the disturbance had reached the shore, but the centre of the tiny storm showed no sign of movement. It was as if, Lora told herself, an invisible finger had reached down from the sky and was stirring the sea.
     Quite abruptly, the entire pattern changed. Now the waves were no longer battering against each other; they were marching in step, moving more and more swiftly in a tight circle. A cone of water was rising from the sea, becoming taller and thinner with every second. Alteady it was a hundred feet high, and the sound of its birth was an angry roaring that filled the air and struck terror into the hearts of all who heard it. All, that is, except the little band of men who had summoned this monster from the deep, and who still stood watching it with calm assurance, ignoring the waves that were breaking almost against their feet.
     Now the spinning tower of water was climbing swiftly up the sky, piercing the clouds like an arrow as it headed toward space. Its foam-capped summit was already lost beyond sight, and from the sky there began to fall a steady shower of rain, the drops abnormally large, like those which prelude a thunderstorm. Not all the water that was being lifted from Thalassa's single ocean was reaching its distant goal; some was escaping from the power that controlled it and was falling back from the edge of space.
     Slowly the watching crowd drifted away, astonishment and fright already yielding to a calm acceptance. Man had been able to control gravity for half a thousand years, and this trick — spectacular though it was — could not be compared with the miracle of hurling a great starship from sun to sun at little short of the speed of light.
     The Earthmen were now walking back toward their machine, clearly satisfied with what they had done. Even at this distance, one could see that they were happy and relaxed — perhaps for the first time since they had reached Thalassa. The water to rebuild the Magellan's shield was on its way out into space, to be shaped and frozen by the other strange forces that these men had made their servants. In a few days, they would be ready to leave, their great interstellar ark as good as new.
     Even until this minute, Lora had hoped that they might fail. There was nothing left of that hope now, as she watched the man-made waterspout lift its burden from the sea. Sometimes it wavered slightly, its base shifting back and forth as if at the balance point between immense and invisible forces. But it was fully under control, and it would do the task that had been set for it.

From THE SONGS OF DISTANT EARTH (short-story version) by Arthur C. Clarke (1958)


In Samuel R. Delany's Triton aka Trouble on Triton, the colony has 1 Terran gravity by virtue of the gravity generator plates. The idea is that an object's mass increased near the speed of light due to relativity. So if a plate was moving real close to lightspeed, it would have enough mass to have enough gravity to bring Triton's pathetic gravity up to 1 gee. How do you keep the plate from vanishing into deep space? You don't make the plate move at lightspeed, you make the atomic nuclei composing the plate spin in place at lightspeed.

This won't work because [a] making a small plate have 1 gee of gravity would require it to be denser than neutronium, which would instantly fall through the ground until it reached Triton's core, [b] it would require more power that Sol emits, and [c] spinning a nuclei that fast would make it fission into subatomic particles.

First Lensman


(ed note: the Hill is Terra's main planetary fortress. The Lensmen knew it was going to be attacked by a huge enemy fleet using a huge number of atom bombs. So they took precautions.)

He gritted his teeth. The scouts and light cruisers were doing their damndest, but they were outnumbered three to one, what a lot of stuff was getting through! The Blacks wouldn’t last long, between the Hill and the heavies, but maybe long enough, at that—the Patrol globe was leaking like a sieve! He voiced a couple of bursts of deep-space profanity and, although he was almost afraid to look, sneaked a quick peek. to see how much was left of the Hill. He looked—and stopped swearing in the middle of a four-letter Anglo-Saxon word.

What he saw simply did not make sense. Those Black bombs should have peeled the armor off of that mountain like the skin off of a nectarine and scattered it from the Pacific to the Mississippi. By now there should be a hole a mile deep where the Hill had been. But there wasn’t. The Hill was still there! It might have shrunk a little—Clayton couldn’t see very well because of the worse-than-incandescent radiance of the practically continuous, sense-battering, world-shaking atomic detonations—but the Hill was still there! And as he stared, chilled and shaken, at that indescribably terrific spectacle, a Black cruiser, holed and helpless, fell toward that armored mountain with an acceleration starkly impossible to credit. And when it struck it did not penetrate, and splash, and crater, as it should have done. Instead, it simply spread out, in a thin layer, over an acre or so of the fortress’ steep and apparently still, armored surface!

“You saw that, Alex? Good. Otherwise you could scarcely believe it,” came Kinnison’s silent voice. “Tell all our ships to stay away. There’s a force of over a hundred thousand G’s acting in a direction normal to every point of our surface. The boys are giving it all the decrement they can—somewhere between distance cube and fourth power—but even so it’s pretty fierce stuff. How about the Bolivar and the Himalaya? Not having much luck catching Mr. Black, are they?”

“Why, I don’t know. I’ll check … No, sir, they aren’t. They report that they are losing ground and will soon lose trace.”

“I was afraid so, from that shape. Rodebush was about the only one who saw it coming … well, we’ll have to redesign and rebuild …”

Port Admiral Kinnison, shortly after directing the foregoing thought, leaned back in his chair and smiled. The battle was practically over. The Hill had come through.

The Rodebush-Bergenholm fields had held her together through the most God-awful session of saturation atomic bombing that any world had ever seen or that the mind of man had ever conceived. And the counter-forces had kept the interior rock from flowing like water. So far, so good.

Her original armor was gone. Converted into …what? For hundreds of feet inward from the surface she was hotter than the reacting slugs of the Hanfords.

Delousing her would be a project, not an operation; millions of cubic yards of material would have to be hauled off into space with tractors and allowed to simmer for a few hundred years; but what of that? Bergenholm had said that the fields would tend to prevent the radioactives from spreading, as they otherwise would—and Virgil Samms was still safe!

From FIRST LENSMAN by E. E. "Doc" Smith (1950)

Heinlein's Childbirth Machine

In his classic novel Time Enough For Love, Robert Heinlein does not go into the details about the paragravity used on starships. But he has the protagonist utilize it in a very unique way.


     Sheffield worried these matters while he led auxiliary controls from the gravistat in the control room to the delivery chair. He had decided that, nuisance though it was, his cabin had to be the delivery room; it was the only compartment with enough deck space, a bed at hand, and its own bath. Oh, well, he could stand the nuisance of squeezing past the pesky thing to reach his desk and wardrobe for the next fifty days—sixty at the outside, if he had Llita’s date of conception right and had judged her progress correctly. Then he could disassemble it and stow it...

     ...He positioned the chair, bolted it to the deck, ran it up to maximum height, placed its midwife’s stool in front of it, adjusted the stool until he was comfortable in it, found he could lower the delivery chair ten or twelve centimeters and still have room to work. That done, he climbed into the delivery chair and fiddled with its adjustments—found that it could be made to fit even a person of his height—predictable; some women on Valhalla were taller than he was...

     ...My stool was bolted to the deck, I had added a seat belt. As I strapped myself down, I reminded them that we had a rough ride coming—and this we had not been able to practice; it would have risked miscarriage. “Lock your fingers, Joe, but let her breathe. Comfortable, Llita?”
     “Uh—” she said breathlessly. “I—I’m starting another one!”
     “Bear down, dear!” I made sure my left foot was positioned for the gravistat control and watched her belly.
     Big one! As it peaked, I switched from one-quarter gravity up to two gravities almost in one motion—and Llita let out a yip and the baby squirted like a watermelon seed right into my hands.
     I dragged my foot back to allow the gravistat to put us back on low gee even as I made a nearly instantaneous inspection of the brat...

     ...But more interesting is the Senior’s allegation that he used a pseudogravity field in that year to facilitate childbirth. Was he the first tocologist to use this (now standard) method? Nowhere does he assert this, and the technique is usually associated with Dr. Virginius Briggs of Secundus Howard Clinic and a much later date.

From TIME ENOUGH FOR LOVE by Robert Heinlein (1973)

To his horror, John F. Ptak discovered that some mad scientist actually tried to patent something similar to this back in 1965. Patent 3216423: Apparatus for facilitating the birth of a child by centrifugal force.

Mr. Ptak notes "I found this by accident, and needed to share it immediately, because in the splendid and chilly vastness of the infinite Encyclopedia of Bad Ideas, this entry would seem quite the poster child for such a stupendous effort—the mud to which all dust aspires." I am inclined to agree with him. Marc Abrahams wrote a great piece exploring this idiotic idea.

The attending gynecologist weighs the expectant mother so that the operator can attach the proper amount of balancing counter weights to the other side of the centrifuge. The gynecologist also determines how many gravities of acceleration will be safe.

Upon birth, the newborn rapidly falls into infant reception net (88) which is lined with wad of cotton (97) to protect the baby when impacts on upright switchout plate (93) which turns off the entire clanking mess.

This very bad idea won the 1999 Ig Nobel Prize in the field of Managed Health Care.

I have no idea if Heinlein was aware of this contraption when he wrote his novel. Probably not, the idea is obvious enough.

Space Skimmer

     At first he didn’t realize what he was seeing. Some kind of an altar, he thought. Six giant slabs spaced equally around a —
     That was his first impression. Something bright and gold and glimmering, Bashing shades of yellow and red and flickering white — copper, bronze, and platinum highlights; dazzling vanes of silver and emerald, amethyst and opal, moonstone and ruby and diamond — something sculptural, clustered, reaching, stretching, describing and making the shape of a spherical sun-burst —
     A frame of some kind — big, more than a hundred feet high —

     A core of silvery shimmering vanes, flashing all colors, diamond-bright; they reached outward in all directions, some farther than others, but almost all ended in planes set at odd angles, no two the same. There were suggestions of platforms and hints of terraces, broad balconies and graceful ramps, places where stanchionlike shapes arced smoothly across from one vane to another. On one of them, he thought he recognized curving steps, but they were upside-down.
     After a long moment, Mass released the breath he was holding; his sigh was the sound of awe.
     He turned his attention to the single bright vane before him, slid his hand back and forth along its still cool, cool surface. It was smooth, almost slippery, so icy and almost greasy to the touch — and so cool, so cool; the touch of his hand warmed it not a bit.
     He stood there looking at it for a long time. A long, long time. The white sun glinted along its surfaces.
     On impulse, he started climbing. He swung himself up into it, arm over arm until he reached one of the wider vanes —
     — tripped and fell sideways — found himself lying flat on his back, a wall of stone and earth to his left, wide emptiness to his right —
     His hands clutched for a hold — slipped along the greasy-feeling, frictionless surface — and realized he wasn’t falling —
     Tentatively, he sat up —
     The emptiness on his right was the sky; the wall of stone and earth on his left, the ground. The horizon was a vertical line ahead, straight where the ocean hung in impossible balance, jagged where the land jutted from it.
     The juxtaposition of earth and sky didn’t hit Mass at first; he was too used to the disconnected orientations of space to be startled and he was too intrigued with examining the surface where he sat. It was untarnished; not a spot of wear or discoloration, no dust, no scratches; just an even, bright plane.
     The feel of it
     — like the feel of a stasis-bite information tab —
     He put his head down close to the surface holding him and looked along it. He straightened and gazed about in wonder — yes, there it was, all around him — the familiar shimmer of a stasis-field, a minute and telltale vagueness describing the edge of every vane and terrace and platform. This metal — if it was metal — would never wear out; it couldn’t — it was motionless in time. This — thing, whatever it was, was indestructible for as long as the stasis endured.
     Mass stood up slowly. Usually a stasis-field was spherical; to generate one that would match the shape of this incredible framework —
     Abruptly he caught sight of the ground below/beside him. He sat down again, suddenly pale.
     He wasn’t falling, he told himself. He wasn’t falling.
     Logically, he knew he wasn’t falling — but his eyes kept telling him he should be. His stomach contracted in fear and confusion. Somehow the ground was twenty feet below him — twenty long feet. A lifetime of conditioning in Streinveldt’s desperate gravity told him a fall that far would be fatal. He clenched his eyes, his fists, his whole body; he went rigid — , He didn’t fall —
     He sat frozen, his eyes tightly shut, and listened to his inner ear. Down was where he was sitting, not where he was looking. He was already down — he wasn’t falling — wasn’t falling —
     He opened an eye.
     He wasn’t falling.
     The sky was to his right, the ground was to his left, the horizon was a vertical division ahead; but he wasn’t falling.
     He forced himself to unclench, forced himself to breathe again, forced himself to swallow. Cold sweat trickled down his side. He relaxed carefully, stifling his fear.
     He even laughed at himself; a hint of a smile on his broad features, embarrassed, almost sheepish.
     Creases appeared at the corners of his wide mouth. He swallowed and his throat still felt tight — and that made him smile some more. He must look silly as hell sitting on the side of a wall and shaking.
     I’m not falling, he told himself again, and stood up slowly.
     He listened to his inner ear; he let that be his guide as to the direction of down and ignored the insistent, but contradictory, information of his eyes. Gradually he became used to this new, surreal orientation. On one side was a wall that stretched up and down, reaching for infinity in each direction.
     On the other side, nothing whiteness. He swallowed, took a breath, then a step.
     Slightly surprised that he didn’t fall, he took another. What had happened was obvious now; there were field-generated gravities here; probably a man could stand on any plane of this framework, at any angle; this “starflake” must be independent of the planet’s influence. Yes, he realized, that would be the source of the singularity he’d detected from space.
     He turned around slowly, surveying the starflake from his vantage point within it. He began moving “upward,” toward its center, walking carefully along a narrowing ramp. He closed his mind against the distorted topography of the planet; he had to. The ramp curved upward, bent through forty-five degrees — but beneath his feet was always down.
     He walked around a twisted shape of sharp metal and suddenly he was at the center. Row, the ground loomed over his head. The empty sky was below the platform on which he stood; he hardly noticed, his attention was focused on —
     An Oracle. Model HA-90.
     He gasped, a sharp intake of breath. Slowly, he approached it, unbelieving. He touched its keyboard and it flashed to life. The scanner plate glowed. Almost without thinking, he slid the translating tab from his pouch and onto the glowing panel. The cuneiforms on the keys became their Streinveldtian equivalents.
     He tapped out carefully, fingers like wooden pegs:
     And underneath the question, the answer appeared:
     He typed, WHAT IS AE’LAU?
     And the Oracle answered, SKIMMER NUMBER 312.
     Skimmer number 312!
     Mass jerked as if stung —
     He whirled about in confusion; the shattering vanes dazzled around him —
     Of course, he realized, staggering with the suddenness of it — he stared at the skimmer anew. Under-standing blazed fierce in his eyes. Of course, of course The skimmer is a stasis-field ship. lt doesn’t need metal walls — the field is both the hull and the means of moving it.
     All a man needs is a place to stand — these shimmering balconies! There’s neither reason nor need for all of them to be in the same up-down, vertical-horizontal orientation. Any field-generated gravity can be manipulated and up and down can be wherever you want them to be; take advantage of that and make maximum utilization of the stasis-enclosed volume — fill it with a spherical framework.
     Mass imagined the craft hanging in space, men standing on both sides of these wide platforms, standing at odd angles throughout the craft, each man carrying his own up-down orientation with him; wherever one was standing, that was down.
     “Yes, of course —” he breathed in awe. Now he knew why they called it “the ultimate spaceship.” No walls, just a framework and a stasis-field hull.
From Space Skimmer by David Gerrolds (1972)

Paragravity Elevators

RocketCat sez

SF writers sometimes try to convince readers the stories are in the futuristic future by making doors dialate. Some got the bright idea of combining paragravity and elevators to make antigravity elevators. Which makes about as much sense as a nuclear powered dishwasher. And for the same reason. Just think about it! Long open elevator shafts with no carriages, full of magically floating people. Futuristic? Yes. Practical? Oh, come now, let's get real here. Sledgehammer to kill a gnat or what? Just to give your novel a George Jetson atmosphere?

The small problem is: antigrav-elevator users wearing skirts or kilts had best not go commando. Not unless they are exhibitionists or advertising.

But the big problem is failure modes.

The elephant in the room is why throw all this high-tech engineering at a solved problem? The answer "to make my scifi novel look really really kewl" just doesn't cut the mustard. But keep in mind that the idea has been used by some top-notch writers.

Paragravity elevators are conventional elevators where the carriage and cables are replaced by an open shaft with columns of flying people buoyed by paragravity fields. It appears in some older science fiction novels, but appears to have fallen out of favor. Which is not surprising since the concept has problems.

Ignoring the embarrassing peek-a-boo view offered by users wearing skirts or kilts, there is the question of failure modes. If a conventional elevator fails, safety devices will detect the carriage's plummet and slam on the emergency brake shoes. If a paragravity elevator fails, there is no carriage, and no carriage emergency brake shoes. The best it can do is snap shut safety nets at each level and try to catch all the falling people. And good luck getting those people to ever step back into a paragravity elevator for the rest of their lives.

There are also questions about how exactly do the users escape the elevator when they arrive at their destination level. Especially considering the tube contains columns of impatient moving people and a floating user has no convenient carriage floor for locomotion. What are they going to do, flap their arms?

And do you double the elevator footprint by having two dedicated elevator shafts, one for going up and one for going down? Or do you take the footprint reducing but dangerous option of somehow having both up and down traffic in a single tube?

(ed note: The protagonists was a spaceman, until the day he had to go EVA to fix the antenna on the spacecraft centrifuge. While it is still spinning. There is an accident and he is flung into space. He quits his spaceman job since he now has a pathological fear of falling. He takes an assumed name "Saunders")

Tully led the way to the elevator; they crowded in. Most of the employees — even the women — preferred to go down via the drop chute, but Tully always used the elevator. ‘Saunders’, of course, never used the drop chute; this had eased them into the habit of lunching together. He knew that the chute was safe, that, even if the power should fail, safety nets would snap across at each floor level — but he could not force himself to step off the edge.

Tully said publicly that a drop-chute landing hurt his arches, but he confided privately to Saunders that he did not trust automatic machinery.

From ORDEAL IN SPACE by Robert Heinlein (1948)

He led the way straight down the hall to a door at the rear, raising his hand to pass it in a swift, decisive gesture over the plate set into its surface. That triggered the opening, and we stood on the edge of a gray shaft. Lugard did take precautions there, tossing his kit bag out. It floated gently, descending very slowly. Seeing that, he calmly followed it. I had to force myself after him, my suspicions of old installations being very near the surface.

We descended two levels, and I sweated out that trip, only too sure that at any minute the cushioning would fail, to dash us on the floor below. But our boots met the surface with hardly a hint of a jar, and we were in the underground storeroom of the hold.

From DARK PIPER by Andre Norton (1968)

     But to their bafflement there seemed to be no way down at all. They threaded rooms and halls, pushing past the remains of furnishings and strange machinery which at other times would have set them speculating for hours, hunting some means of descent. None appeared to ­exist—only two stairways leading up.
     In the end they discovered what they wanted in the center of a room. It was a dark well, a black hole in which the beam of Kartr’s flash found no end. Although the light did not reveal much it helped them in another way because its owner dropped it. He gave an exclamation and made a futile grab—much too late. Rolth supplied an excited comment, reverting in this stress to his native dialect and only making sense when Kartr ­demanded harshly that he translate.
     “It did not fall! It is floating down—floating!”
     The sergeant sat back on his heels. “Inverse descent! Still working!” He could hardly believe that. Small articles might possibly be upborne by the gravity-dispelling rays—but something heavier—a man—say—
     Before he could protest Rolth edged over the rim, to dangle by his hands.
     “It’s working all right! I’m treading air. Here goes!”
     His hands disappeared and he was gone. But his voice came up the shaft.
     “Still walking on air! Come on in, the swimming’s fine!”
     Fine for Rolth maybe who could see where he was going. To lower oneself into that black maw and hope that the anti-gravity was not going to fail—! Not for the first time in his career with the rangers Kartr silently cursed his overvivid imagination as he allowed his boots to drop into the thin air of the well. He involuntarily closed his eyes and muttered a half-plea to the Spirit of Space as he let go.
     But he was floating! The air closed about his body with almost tangible support. He was descending, of course, but at the rate of a feather on a light breeze. Far below he saw the blue light of Rolth’s torch. The other had reached bottom. Kartr drew his feet together and tried to aim his body toward the pinprick of light.
“Happy planeting!” Rolth greeted the sergeant as he landed lightly, his knees slightly bent, and with no shock at all. “Come and see what I have found.”

From STAR RANGERS by Andre Norton (1953)

It opened at his approach, and he stepped through it into a yawning, brightly lit void over a thousand kilometers deep. He’d braced himself for it yet he knew he appeared less calm than he would have liked—and felt even less calm than he managed to look as he plunged downward at an instantly attained velocity of just over twenty thousand kilometers per hour.

(Ship's Computer) Dahak had stepped his transit shafts’ speed down out of deference to his captain and Terra-born crew, though Colin knew the computer truly didn’t comprehend why they felt such terror. It was bad enough aboard the starship’s sublight parasites, yet the biggest of those warships massed scarcely eighty thousand tons. In something that tiny, there was barely time to feel afraid before the journey was over, but even at this speed it would take almost ten minutes to cross Dahak’s titanic hull, and the lack of any subjective sense of movement made it almost worse.

Yet the captain’s quarters were scarcely a hundred kilometers from Command One—a mere nothing aboard Dahak—and the entire journey took only eighteen seconds. Which was no more than seventeen seconds too long, Colin reflected as he came to a sudden halt. He stepped shakily into a carpeted corridor, glad none of his crew were present to note the slight give in his knees as he approached Command One’s massive hatch.


(ed note: this paragravity elevator actually has a carriage)

The elevator was of the new sort that ran by gravitic repulsion. Gaal entered and others flowed in behind him. The operator closed a contact. For a moment, Gaal felt suspended in space as gravity switched to zero, and then he had weight again in small measure as the elevator accelerated upward. Deceleration followed and his feet left the floor. He squawked against his will.

The operator called out, “Tuck your feet under the railing. Can’t you read the sign?”

The others had done so. They were smiling at him as he madly and vainly tried to clamber back down the wall. Their shoes pressed upward against the chromium of the railings that stretched across the floor in parallels set two feet apart. He had noticed those railings on entering and had ignored them.

Then a hand reached out and pulled him down.

From FOUNDATION by Isaac Asimov (1951)

Conspiracy Theory

Ufologists and conspiracy theorists are fond of speaking in breathless tones about something called "electrogravitics", that can convert electricity into gravity. Unfortunately it appears to be about as valid as chemtrails, Bigfoot, the Loch Ness Monster, and sightings of Elvis.

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