Science fiction writers who are writing about interstellar empires might want to contemplate the upheaval caused when the empire reaches "peak antimatter". Also interesting is how the rise of the 17th century Dutch seaborne empire was due in part to their superior utilization of wind energy, in the form of the Fluyt ship. The galactic mercantile empire of the Technomorphs' could be based on the remarkably efficient zero-point-energy reactors of their trader starships.
Ever since Asimov's Foundation novels, the Roman Empire was the model for the Galactic Empire. The fall of the Roman Empire was hastened by invading barbarians hordes from the empire's rim (mostly Goths). So of course the decadent Galactic Empire has to be threatened by Space Barbarians in their interstellar long-ships at the rim of the galaxy.
In science fiction, arguably the most well developed example of this theme is the barbarian Mercians in Poul Anderson's Dominic Flandry novels (though the Mercians became barbarians in Supernova, a David Falkayn story).
The traditional method to create barbarians is for some well-meaning but naive star-travelers to give starship technology to a primitive planet-bound species. The barbarians then proceed to raid all the civilized planets in range, like space-going vikings. The civilized military will (hopefully) eventually put down the barbarians but the war will be long, bloody, and costly. After the barbarian wars, the star-traveling civilization outlaws such technology transfers. Assuming the civilization actually survives the barbarian onslaught.
Of course after the Anti-Barbarian Act of 2500 passes, some criminals will be tempted to break it in exchange for barbarian gold.
However, the concept of primitive barbarians using starships has problems. One wonders about the tech assumptions. Either starships are relatively cheap (ponder the idea of "barbarians" fielding aircraft carriers as a comparison) or the smallest feudal units are pretty good sized. This is sort of addressed in the link above about barbarian gold, and more generally discussed in the section The Sword on the Starship.
There are some practical question about whether a government on the scale of a galactic empire could function, mostly because bureaucracy has poor scalability.
For me, this is one of those gray areas in the writing of science fiction novels. Much like faster-than-light starships in fact. Yes, it may be impossible. But you want it, your readers want it, everybody's doing it.
As a point of terminology, the marches or boondocks of a galactic empire are generally called the "rim" or the "fringe." This represents the astrographical limit of imperial control.
If you are actually trying to make a full fledged interstellar empire, the maximum speed of starships and the maximum speed of communications limits the maximum size of the empire. Timelag creates Limits On Reaction Time. If it takes a year for news of a rebellion on the outer marches of the empire to reach the capital (or sector capital) and another year for a fleet to travel back, this means the rebels will have two years to win the rebellion and fortify in preparation for the arrival of the imperial starfleet.
The defining factor of whether a given planet was part of an empire or not is whether the time delay between the start of the rebellion and the arrival of the imperial punishment fleet is longer than the time required for the rebellious planet to manufacture enough defenses to take care of the punishment fleet.
In other words: if you cannot hold on to the planet, it ain't yours.
An auxiliary factor is the expected size of the punishment fleet. This will depend upon many other factors. A worthless rock-pile might only rate one warship, while The Planet Of Immortality Drugs could get a sky full of ships. An average planet in the middle of the empire could rate a sizable fleet since it could be a nucleus of rebellion for other planets, while the same planet out on the galactic marches of the empire might not get anything.
The expected size of the punishment fleet defines how many defenses need to be manufactured. And the amount of defenses is a big factor in determining whether it is possible to manufacture all of them before the fleet shows up.
Historically on Terra, communication by travel came first (runners, horseback couriers, boat and rail-road train). Later non-travel communication was invented (telegraph and radio), and it was much faster than travel communication.
According to SpaceMike, historically we can use these as general rules:
The largest pre-telegraphy empire By Land was the Mongol Empire. The communication time from the central capital to the rim (or vice versa) was 12 weeks. The empire had a radius of about 5,000 kilometers, and a horse courier could travel about 60 km/day.
The largest pre-telegraphy empire By Sea was a toss-up between the Spanish and the Portugese, though arguably the Dutch went further. It took about 13 weeks to travel from the capital to the furthest colony of the empire. A good ship could cross the Atlantic ocean in about ten weeks, then a few more weeks to go over land to the colony.
So if the galactic empire has no FTL radio but does have FTL courier starships, the speed of the ships and the maximum allowed radius of the empire have to be adjusted so that the ship takes 10 to 15 weeks or so to travel from the central capital to the rim (or vice versa).
Early telegraph had an effective speed of about 1,600 km/hour. So it could send a message from the Mongol capital to the rim in about three hours. Which was a vast improvement over 12 weeks. Radio of course travels at the speed of light, for the Mongol empire it is effectively instantaneous.
Before the age of horseback couriers, information technology ranged from "coconut wireless" (gossip and rumors spread neighbor to neighbor), pigeon post and war pigeons (range 1,800 km, speed 80 km/h), smoke signals (on the Great Wall of China soldiers could transmit warnings 750 km in a few hours, Gondor Style ), and talking drums (160 km/hr).
Smoke signals and talking drums are hard to interfere with by enemy action. However, during World War I and II soldiers were trained to shoot at war pigeons and some actually kept hawks to intercept the pigeons. Stop that pigeon now! A pigeon named Cher Ami was awarded the French "Croix de Guerre with Palm" for heroic service by virtue of delivering messages that saved the lives of 194 US soldiers of the 77th Infantry Division's "Lost Battalion" in 1918. She delivered the message despite having been shot through the breast, blinded in one eye, and had a leg hanging only by a tendon.
Now, as a science fiction author, all you have to do is brainstorm an interstellar equivalent to smoke signals and homing pigeons.
Calculating Control Radius
So, given a maximum timelag and the speed of your FTL warships and/or radio, the maxium radius of your empire can be calculated. This assumes that the imperial capital is located at the center of the sphere, but see below. Alternatively, given the maximum timelag and the desired radius, the speed of the FTL warships/radio can be calculated. It comes down to the ancient equation Distance equals Rate time Time.
ControlRadius = FTL_Lightspeeds * Maximum_Timelag
FTL_Lightspeeds = ControlRadius / Maximum_Timelag
ControlRadius = distance from Imperial Capital and the rim of the empire (light-years)
FTL_Lightspeeds = velocity of FTL starships and/or FTL radio (multiples of lightspeed, or "c")
Maximum_Timelag = maximum allowed time for a message to travel from the capital to the rim (years)
According to the above estimates, this is around 0.19 years (10 weeks) to 0.29 years (15 weeks), averaging to 0.23 years (12 weeks). Take your pick.
|1||Radius of solar system Oort Cloud|
|15||Sol's interstellar neighborhood|
|20||Nearest 100 stars|
|30||Average half-light radius of typical globular cluster|
|200||Local Bubble, radius of Poul Anderson's Terran empire|
|1000||Approximate thickness of galaxy centered on Sol|
|25,000||Distance from Sol to galactic core|
|50,000||Radius of the galaxy|
Note the off-hand reference to "sector capitals" above. If your communications/warship speed dictate that your empire can be no more than X parsecs wide with central control in the capital then you can obviously make your empire larger than X if you delegate control to a series of sub-capitals at some distance. For maximum safety, the sub-capitals should be no further from the capital than X. If the empire wants to push its luck, it can trust the sub-sector governors a bit more and located the sub-capitals further than X. This allows the empire to be wider, but more unstable.
In ancient Rome such divisions were called an Imperial Province. Ever since Isaac Asimov wrote his Foundation trilogy, divisions in a galactic empire are called "sectors" (though classic Star Trek messed up and called them "quadrants").
Asimov also popularized the naming of sectors after the brightest star contained. This meant that Sol was located in the "Sirius sector", since Sirius has an intense absolute magnitude of 1.4 and is a mere 8.6 light-years from Sol. Vega is much brighter with an absolute magnitude of 0.58, but is much farther away at 25 light-years. Poul Anderson's novels The Rebel Worlds and its sequel The Day Of Their Return are set in "Sector Alpha Crucis".
Of course sector captial rule runs the risk of an ambitious sector governor getting ideas about declaring independence from the Empire. On the other hand the sector governor had better be real sure of their chances for success. Empires consider breakaway sectors to be what you call "existential threats"; so the reaction tends to be swift, overwhelming, and harsh.
Arthur C. Clarke insists that large galactic governments are impossible because of their intolerable complexity. This is based upon a simple truth: As population grows arithmetically, the number of possible interactions rises geometrically.
...But all such attempts to showcase the "numbing complexity" of galactic government are unconvincing because information flows in interstellar empires needn't be all that serious, though we'll obviously need computer-bureaucrats to handle most of the red tape.
... Since silicon microcircuits can theoretically process ten billion times more data than human neurons, pound for pound and bit for bit, then maybe with computer help humans could run empires ten billion times larger than the historical imperial scale. The pre-computer Roman and British Empires ruled 30 million and 300 million people, respectively, before becoming too large. Perhaps a galactic empire using electronic administrators could handle 1019 people before it got too cumbersome. That's a billion planets with ten billion inhabitants each!
...According to Mosca's Rule: "The larger the political community, the smaller will be the proportion of the governing minority to the governed majority." Roberto Michels' "Iron Law of Oligarchy" goes still farther; asserting that growing political systems, especially empires, invariably evolve into more oligarchic (rule by the few) forms of government. So while democratic or republic empires are possible, as they grow they will slowly but implacably drift towards autocracy.
...Specialization leads to hierarchy and span of control. Hierarchy means levels of increasing managerial specialization, each level having supervisors of equal responsibility. Span of control is the number of subordinates administered by each supervisor.
Studies of government and private organizations show that the number of hierarchical levels and the span of control tends to increase as the whole system expands, but also that the two are complementary. For a given size, a wider span of control means fewer levels are needed above and below each span, producing a broad "flat" organizational pyramid. More levels means small spans suffice, giving a narrow "tall" organization with tighter control from the top. Humans seem naturally to prefer rather tall organizations, perhaps partially due to our simian heritage of vertical troupe dominance chains. Sentient extraterrestrials evolved from carnivorous cats or intelligent octopi, solitary creatures by nature, would favor flatter organizational structures.
...The best human organizations have spans of five subordinates per supervisor. Using this figure, a galactic empire controlling ten billion planets having ten billion inhabitants each would require at least 21 hierarchical levels. It is well known that human organizations with more than 6-8 levels become excessively bureaucratic.
...If we optimistically assume that a control span of 100 subordinates can be achieved for, say, human policymakers, then the number of hierarchical levels can almost be halved - from 21 down to 11. The structure of Sir Roger's bustling empire might then look something like Figure 1.
Sir Roger's Galactic Empire
(Span of control ~=100, Hierarchical Levels ~=11)
1 Emperor 1 1010 1020 2 Cabinet Minister 100 108 1018 3 Peer 10,000 106 1016 4 Royal Magistrate 106 10,000 1014 5 Starkeeper 108 100 1012 6 Planetary Governor 1010 1 1010 7 Continental Regent 1012 108 8 Knight 1014 106 9 Burgess 1016 10,000 10 Gentry 1018 100 11 Commoners 1020 1
Even with all this mechanized assistants, the Emperor will have absolutely no contact with non-interstellar personnel. His relationship with his magistrates would not be unlike those between the United States President and the mayors and city managers of American cities. To the Galactic Emperor, the starkeepers, each responsible for 100 worlds, will seem much as U.S. citizens appear to their President - with only a very rare audience being granted. Planetary governors are "the rabble."
Organizational specialist studying "control loss theory" say that in tall, human-like galactic organizations, memos would have to travel down through so many channels that most orders from top to bottom levels could be almost totally degraded to noise by they time they arrive. Economist Oliver Williamson devised a simple model to predict how goals generated at the top of a hierarchy are implemented at the bottom after passing down a number of levels in the chain of command.
If each message, on average, passes through a level 95% intact, then Williamson would claim that since orders must change hands 10 times, Sir Roger's Empire is (0.95)10 = 60% effective in carrying out its aims. At 85% per level (Williamson's lower limit based on studies of actual human organizations), effectiveness drops to 20% and only one-fifth of the Emperor's plans for the commoners ever reach fruition.
Peter B. Evans uses Williamson's control loss model to show that higher efficiencies are possible when the Emperor switches to "multiple hierarchy" systems, such as the dual hierarchy. If the Emperor creates a complete second command hierarchy in parallel with the first, his effectiveness rises by nearly two-thirds. The superiority of dual hierarchies is well-known in business (line-and-staff) and in public administration (especially Communist bureaucracies). Lattice structure systems are a more sophisticated form, involving a complete lattice of hierarchial links providing a startling multiplicity of pathways to the top. Such novel system my not encourage galactic stability, but the opportunities for palace intrigue are legion!
The solution is to get rid of central control. But doesn't that mean the resulting chaos ain't an "empire" any more? Maybe, but maybe not. Let's talk about termites and ants.
Look at that picture of a splendid termite mound. It is comparable to Antonio Gaudí’s church. Surprisingly, the termite mound was not constructed under any sort of centralized control. In fact, the workers cannot even perceive the overall shape of the mound (worker termites are blind). Yet the mound is built including elaborate arches. It even incorporates galleries and chimneys to manage temperature and humidity. How is this possible?
Termites use "bottom-up" management instead of the "top-down" management used with central control. Even though a given termite only has a miserable 2-volt brain it still has just enough intelligence to perform specific actions (e.g., glue your grain of sand on that growing pillar there) when triggered by local cues (scent pheromones by other local termites, temperature and humidity conditions, etc.). A bunch of simplistic actions can achieve surprisingly sophisticated result by the magic of Emergent Behavior.
The point is: management by emergent behavior is infinitely scalable. There is no size limit. Galactic "empire," here we come.
Granted, this is not going to look like the empire from Star Wars or Asimov's Foundation. But it has the virtue of being actually workable. It might look more like a nomadic empire.
It also would be a very good fit for an alien empire that had a hive mentality, since they are traditionally portrayed as insect-like aliens to start with.
Yes, human beings are more intelligent than ants. That's not the point, in such an empire the operative units might be the equivalent of a division within a corporation. Such divisions often exhibit less intelligence than your average ant.
Taken to an extreme, a galactic empire could be modeld on your typical slime mold, which is actually a colony creature that is a congomeration of single-celled critters. in 2016 scientists were flabbergasted when they discovered a slime mold was capable of learning, even though the blasted thing did not have a brain.
Even the process of fighting off an enemy starfleet can be handled this way. The defense can be handled locally as an artificial immune system.
One of the draw-backs of emergent management can be seen in ant-hills. It is not unusual to see an ant-hill at war with itself. Since there is no central control, the various local groups have no way of knowing that the other group is part of the same hill.
There are several terms associated with this process, some of which overlap.
Many species of ants communicate with their nest-mates using chemical scents known as pheromones. Pheromones can be used in many ways by ants and other animals (including humans), but we are most interested in how ants use pheromones to direct each other through their environment — this particular task is closely related to the problem of directing the flow of information through a network.
Consider a colony of ants that is searching for food. Casual observation of an ant colony will reveal that ants often walk in a straight line between their anthill and the food source. The concept of an "army" of ants marching in file has permeated popular culture, and most people who live in ant-friendly locations (nearly every human-friendly place in the world) have seen this particular behavior first-hand. Marching in a straight line, which is usually the shortest route, seems like an obvious solution to the problem of efficient food transportation, and we might pass it off as uninteresting.
Of course, we humans would do the same thing, and in fact we do march in lines along direct routes when we travel in groups as caravans. When we look down at a line of ants from above, we might simply think "so what?" But we have huge brains compared to ants, along with extraordinarily complicated visual systems (over 25% of the human brain is devoted to vision), and we also have a more elevated view of the terrain. Even with these advantages, efficient route-finding, especially through an environment that is full of obstacles, is not an easy task for us. Given ants' comparatively simpler brains, we cannot pass their collectively intelligent route-finding off as trivial. So how do they do it?
Suppose that an ant colony starts out with no information about the location food in the environment. The human strategy in this case would be to send out a "search party" to comb the surrounding area — the scouts who find food can bring some back to the home-base and inform the others about where the food is. Ants do search for food by walking randomly, which is similar to the human "combing" approach, but two issues prevent ants from implementing a human-style search party directly. First, how can an ant-scout, upon discovering food, find its way back to the nest? Second, even if a scout makes it back to the nest, how can it inform the other ants about the food's location? The answers lie in a clever use of pheromones.
To solve the "finding home" problem, each ant leaves a trail of pheromone as it looks for food. In the following example pictures, the pheromone trail left by each wandering ant is shown in transparent red.
When an ant finds food, it can follow its own pheromone trail back to the nest — this is similar to leaving a trail of bread crumbs through the woods to find your way back home. On the way back to the nest, the ant solves the "telling others" problem by laying down more pheromone, creating a trail with an even stronger scent. In the following picture, ant A reaches the food first and then follows its own trail back to the nest, while the other three ants keep wandering.
When other ants run into a trail of pheromone, they give up their own search and start following the trail. In the following picture, ant D discovers the double-strength trail left by ant A and starts to follow it. Ant C encounters the single-strength trail left by D and follows that trail, which will eventually lead to A's trail as well. Ant B eventually discovers its own route to the food source that is completely disconnected from the routed used by A.
If a pheromone trail leads an ant back to the nest with empty jaws, it turns around and follows the trail in the opposite direction. Once an ant reaches the food, it grabs a piece and turns around, following the same trail back to the nest. On the way back, an ant reinforces the trail by laying down more pheromone. In the following picture, ant C joins A's trail but follows it it the wrong direction, reaching the nest empty-jawed. Ant B follows its own trail back to the nest — it never comes in contact with the more direct trail that the other ants are using. A and D carry food back to the nest along the established route.
Once they reach the food, they grab a piece and turn around, following the same trail back to the nest. On the way back, they reinforce the trail by laying down more pheromone.
We have explained how ants find food in the first place, but how do they find the shortest route to the food? One more detail helps to answer this question: ants prefer to follow the trails with the strongest pheromone scent. Shorter routes between the nest and the food are completed faster by each ant that takes them. For example, if ant X is traveling along a 10-meter path to the food repeatedly, and ant Y is traveling along a different 20-meter path repeatedly, ant X will make twice as many trips in an hour as ant Y. Thus, ant X will lay twice as much pheromone on its trail as ant Y. Given the choice, ants will prefer the strongly-scented 10-meter path over the more weakly-scented 20-meter path. The following picture demonstrates this point. When B deposits food at the nest and sets out for another trip, it discovers the strongly-scented path used by the other ants and abandons its own path. At this point, all four ants are using the path discovered by ant A to carry food between the source and the nest.
Over time, many paths between the nest and the food are explored, but the scent on shortest path is reinforced more than the other paths, so it quickly becomes the most popular path, and soon all of the ants walk in file along it.
The ant approach to route-finding is quite different from the way humans navigate their environment. We would visually study the environment as a whole and try to "plan" the best route ahead of time. Of course, the ant method has advantages over our "high level" approach. For example, the ant method works fine in complete darkness. When it comes to navigating without visual cues, humans are comparatively helpless.
The ant method can be distilled into simple rules followed by each member of the colony:
Condition: Action: Not carrying food
Not on pheromone trail
Not carrying food
On pheromone trail
Follow pheromone trail
Lay more pheromone
Reach home without food
On pheromone trail
Follow trail in opposite direction
Reach food Pick up food
Follow trail in opposite direction
Carrying food Follow trail
Lay more pheromone
Reach home with food Deposit food
Follow trail in opposite direction
Though the table of "Simple Rules" above is relatively easy to understand, it still contains seven rules, which is not as simple as we might like. Also, there is a bit of sub-optimal behavior lurking: an empty-jawed ant may follow a pheromone trail in the wrong direction, all the way back to the nest. Of course, when an empty-jawed ant reaches the nest, it turns around and eventually makes its way back to the food, but this is still a wasted trip. The problem seems to be the lack of directionality in the trail, and it is certainly difficult to represent direction when all you have to work with are spots of chemical scents.
In the world of networking programs, we are not limited to directionless trail markers. By adding direction to the trail markers, we actually get a much simpler set of rules
Suppose that we augment the ants with two types of pheromone instead of just one, and suppose that we give these pheromones directionality. The first pheromone can be thought of as a "this way home" marker, and we will call it a home-finding pheromone. The second pheromone will be the food-finding pheromone, and it points in the direction of the food source. When ants leave the nest in search of food, they walk randomly, leaving trails of home-finding pheromone as they go. When an ant finds food, it picks up a piece and follows its home-finding trail back to the nest, leaving a trail of food-finding pheromone as it goes. If a wandering ant ever encounters a food-finding trail, it follows that trail to the food source, leaving more home-finding pheromone as it goes.
This simple modification reduces the complexity of our rule set:
Condition: Walk: Mark Ground With: Not carrying food on food-direction trail, or randomly otherwise home-direction pheromone Carrying food on home-direction trail food-direction pheromone
The good thing is that self-organizing swarm intelligence allows a galactic empire of any size. It is infinitely scaleable.
The bad news is that since is impossible to to have an administrator looking at the big picture, swarm intelligence is vulnerable to a critical flaw. I give you the so called "Ant Mill" aka "Ant Death Spiral."
Offhand, I only see two solutions:
- Allow infinite scaleability by accepting the price that some galactic units are going to die in ant mills
- Reduce scaleability by adding some sort of intelligent agents who can see the big picture and break up ant mills