The larger a government gets, the more bureaucracy it accretes, the easier for things to slip between the cracks, the harder for things to get done. And that's on earth. Imagine a galaxy full of inhabited planets, with billions of people on each one, and probably not a Planet of Hats. Even an FTL drive and form of communication would not decrease the disadvantages of scale. Without the communication, difficulties would be increased -- massively so if only STL travel is possible. Worse yet, mix in aliens with their alien thought paths -- but it would be impossible even with a wholy human galaxy, or a substantial portion of it, or even a solar system well filled up with inhabitable locations. Sci-Fi Writers Have No Sense of Scale, but sometimes, they realize that human government can not reach that far. This may lead to An Aesop about Pride and how man's reach exceeds his grasp in trying to control such a massive space. Often the cause of Vestigial Empire...IN SPACE!
- Serenity mentions offhand that despite the Anglo-Sino Alliance having jurisdiction over the entire star system in which the Firefly franchise takes place, they don't have the manpower to provide effective security everywhere. On a lot of the more sparsely populated planets and moons they contract out to private companies.
- In Poul Anderson's "Starfog" Laure explains that they are too large and disorganized to provide assistance to the spaceship. True, they have the money, here and there, but they do not have the focus to gather it up.
- In Michael Flynn's Spiral Arm series, two sections of the galaxy are nominally controlled. It is observed that the Ardry's authority really runs to wherever his Hounds are operating and no farther. In On The Razor's Edge, a character makes a point that the Ouroborus Circle means that the Ardry has more control.
- In the Worlds of Shadow series, the Galactic Empire has telepathic mutants for communication, but outback worlds, such as the asteroid that the protagonists land on, can pretty much do what they like including keeping slaves, since it takes months to get anywhere by ship.
- In the Honorverse the exodus from Earth lead to the creation of several star nations, most prominently Manticore and Haven. The oldest and largest is the Solarian League, which eventually becomes so large and bureaucratic that it begins to collapse under its own weight.
- Warhammer 40,000:
- In the Imperium of Man individual planets are normally self-governing, with taxes and men for Imperial regiments being gathered by an administration stiff and bureaucratic, operating on its own and not controlled from the top.
- 40K has another example with the Tau Empire, which consists of well-regulated, disciplined and highly organized planet systems where every citizen does his part without hesitation. This is possible for two reasons: the Tau operate on Happiness in Slavery where no citizen will ever try to do less than their rigidly-defined part for the Greater Good (possibly via pheromonal mind control of their ruling class), and their empire is very restrained (their form of FTL travel is something like five times slower than Warp travel, which can often take months of real-time).
- The Third Imperium of Traveller can best be described as a "feudal confederation", individual planets are typically left to their own devices so long as they don't attempt to secede, withhold taxes, interfere with interstellar trade, or make war with other planets. Wars between factions on the same planet are allowed if they don't use nukes or violate any of the other rules. The Imperial Nobility primarily administrate the Imperial Ministries operating within their domains, and have hereditary posts because the Imperium is too large to advance upwards within one lifetime. And the Imperium doesn't govern anywhere near the entire galaxy, or even all of Humaniti, they're bordered by five other empires that are similarly decentralized (save for the K'kree, whose system of government was so inflexible they had to stop at 2,000 worlds).
- ''Halo: As humanity expanded, insurgents began to spring up on colony worlds away from the central government, prompting the UNSC to take action and eventually lead to the creation of the SPARTANs.
- Mass Effect: The galaxy is, according to the Codex, barely 1% explored, let alone governed. Even among the settled worlds, there are territories that the Citadel Council has no authority over, such as the terminus systems, and others where there is no law at all.
- In the Orion's Arm galaxy, not even Sufficiently Advanced Artificial Intelligences prove able to rule an entire galaxy. This synopsis explains some of the difficulties any space empire would likely encounter. In fact they don't rule anywhere near the entire galaxy. On this map all the Sephirotic Empires are within that fuzzy green dot (it's been only 10,500 years, and the setting does not have FTL).
- See The Atomic Rockets page on Galactic Empires for an exhaustive analysis of the logistics of governing an interstellar empire.
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