Setting: Galactic Empire, part 1

A while ago, I decided I wanted to read some science fiction about a galaxy-spanning empire. I briefly browsed Amazon’s kindle offerings under “galactic empire”, but all I found was military sci-fi where the galaxy-spanning nature of the empire wasn’t a major element in the story. Thinking back to classic sci-fi, I’m only coming up with Asimov’s foundation series. It’s possible novels set in the Star Wars or Star Trek universes might have some of what I’m looking for, but off-hand, I don’t even know how big their empires are. I’d appreciate reading recommendations in the comments below.

Since I didn’t find many galactic-empire stories, I decided to put down some thoughts to help sci-fi authors.  I’m thinking of a mostly-human galaxy as I write this, but the concepts could apply in an empire composed of thousands of alien species.

First, let’s make sure we understand how huge a galaxy is. If you don’t know, read this wikipedia article.  I’ve read a number of sci-fi stories where it’s obvious the author didn’t know the difference between a galaxy and a star.  You can see what I think of such authors by reading the second short-story review on this page.

Since some or all of the characters in our story will be humans, let’s set our galactic empire in the Milky Way.  Assuming people still live primarily on planets, how big will the empire be?

Most astronomers think that the Milky Way has 100-400 billion stars, although there are some much higher estimates.  Astronomy isn’t my field, but I skimmed a scientific paper, found at, whose authors think that 1.2% of stars might have habitable planets.  However, they assume that 75% of those planets would be tidally locked.  I’m thinking that a tidally-locked planet wouldn’t be a nice habitat, due to high winds and the planet’s moisture being deposited on the dark side.  Still, even using the conservative 100 billion figure, 0.3% gives our empire three hundred million planets to work with!

The above paper uses the word “habitable” differently from science fiction.  The authors are thinking in SETI terms, looking at planets with the potential for life to evolve independently over billions of years, without being wiped out by radiation from a supernova.  If our science-fiction galaxy was populated by other means such as panspermia, an elder alien race, or creation by God (or gods), then many more planets could be “habitable”.  The same would be true if our empire puts time and effort into terraforming.  For now, I’m going to stick with the most-conservative 300 million figure.

Does our empire actually rule the entire galaxy?  Let’s look at some empires on Earth.  The well-known empires of Alexander the Great, Rome, and the Ottoman Turks didn’t even reach 4% of the Earth’s surface area.  Still, 4% of our galaxy would give an empire over ten million planets.  Alexander’s empire didn’t last long enough to say much about, but Rome and the Ottoman Empire were overrun militarily, so maybe 4% doesn’t cut it.

The Russians and Mongols weighed in closer to 16%, which might give our empire a respectable forty-eight million planets.  Genghis’ Mongol Empire didn’t last, and Russia faced some pretty serious invasions that were defeated with outside help.

Let’s go to the largest one, the British Empire.  Its 24% would give us a whopping seventy-two million planets.  Still, Earth’s British Empire fell after two victorious wars against Germany, and needed outside help for both victories.

Would 50% be enough to keep our empire secure?  Maybe, but what if the other 50% were in the hands of a second empire?  Cold War scenarios could play out, or there could be a never-ending war of attrition between the two empires.  Jack Campbell’s Lost Fleet Series heads in this direction, but doesn’t go full galaxy.

If our empire has a technological edge, maybe it rules most or all of the galaxy.  The full 300 million planets.  You can easily double, triple, or quadruple that number if you want to use higher star system estimates, increase the likelihood of planets being habitable, or give your empire extreme terraforming capabilities.

My next few posts will look at economic, military, social, and political aspects of a galaxy-spanning empire.  I’ll try not to think too small, but I will fail.  The galaxy is just too dang big.

Update: Part 2 has been posted


  1. Interdasting.

    I think in most settings “galaxy-wide” is like “the fate of the planet is at stake” in a fantasy novel. Sure, it may be a whole planet, but in practice, everything happens in two counties and a little excursion to some exotic locale.

    1. Probably difficult for the hero to have enough impact the larger the setting gets, unless the story takes place right at the center of power, or the hero has a magic ring to destroy.

  2. It is people like you who make BIG government possible! ;stop giving them ideas 😉

    My first thought was Neal Asher’s Polity series. But I am not sure it is galaxy spanning and it definitely isn’t monolithic, what with having a border with an alien giant-crab species.

    1. Yeah, they might start hiring bureaucrats in advance, to manage all these colony worlds.

      I’ve got some Asher books on my list to look at, but haven’t read any yet. Maybe I’ll move them up.

      1. there you go again, giving them ideas!

  3. If you keep it hard sci fi, administering a planet of tens of millions of planets tens of thousands of lightyears away from each other would make running the Mongol empire look easy. Which could make for some very interesting science fiction.

    1. I’ve got a brief discussion of this in one of the follow-up posts. I think they’d have to use AI to effectively manage so much information coming at the top leadership, or the bureaucracy would just be out there doing its own thing and ignoring the leaders.

  4. Forrice · · Reply

    Oh hey Neil Clark anthology book Galactic Empires is being published later this month.

    1. Thanks, I’ll have to pick up a copy. I’ll be reviewing a much older galactic empire anthology put together by Asimov after I finish this series of posts.

  5. I always thought Dune did a good job of showing a vast galactic empire at work. So did Speaker for the Dead and some of the other sequels to Ender’s Game.

    Specifically, I liked how the vast majority of people in these books–the common folk, if you will–are still sort of planet-bound. They may live on some distant colony world, but they still spend their entire lives on just that one world. Interstellar commerce, interstellar politics, and interstellar war are all big, costly affairs. Very, very few people get to travel and experience the immense scale of the universe.

    I think that’s a good way to do the vast space empire thing while still emphasizing that we humans are very small.

    1. I hadn’t thought about Dune. I read it so long ago that I remember some of the house politics stuff and the desert environment stuff, but didn’t remember the scale of the galaxy.

      My next galactic empire post will discuss the combination of transportation speed and expense, and how it shapes the empire.

      1. Dune only hints at the scale of the galaxy, it never comes out and says it–which is I think the way to handle it. I look forward to your next post on this subject.

  6. Frank Herbert also wrote the ConSentiency milieu (The Dosadi Experiment, Whipping Star) which were intergalactic.
    For a different flavor of style, there’s the Inquestor series (including The Light on the Sound, The Darkling Wind) by Somtow Sucharitkul (aka S P Somtow).
    And I noticed the Ender Milieu already mentioned.

    There were numerous other intergalactic novels & series back when I first started reading science fiction, but over time, too many new ones failed in the attempt to be great sprawling works and just went splat instead. Nowadays, it’s tough to find any newer works in what’s become a neglected sub-genre rather than a vanguard genre. Building such an immense, cohesive, and workable civilization isn’t the kind of writing an author can quickly knock together, so it seems fewer writers tackle such brave new intergalactic worlds.

    1. I, too, thought of Herbert when I read this. Great post, by the way. I’ll be looking forward to the next installments.

      1. Thanks, I’m planning three more posts over the next two weeks.

    2. Ack! Whipping Star is one of my least-favorite sci-fi works!

      I’ll look at your other recommendations. I forgot James mentioned Ender’s universe, I haven’t read any of the sequels.

      A friend of mine has recommended Ian Banks for some large-scale stuff.

      Now that you mention it, I can see how an author might go all-out with the worldbuilding, and forget to include an actual story.

  7. There was Poul Anderson’s series with Flandry, a spy tasked with keeping the galactic empire from falling (so I’m told — I’ve never read that part of Anderson’s work).

    Brian Aldiss did a fun two volume anthology called Galactic Empires with some good stories, but probably too diffuse for what you’re looking for.

    Pournelle and Niven’s CoDominium books have an interstellar empire but not really big enough to be galactic.

    Satraps run by AIs is an interesting idea.

    1. I’ll look through your suggestions and see if I come up with something interesting, except the CoDominium, because I read those when I was younger. Now I wish I hadn’t given them all away, so I could flip through them.

  8. […] part 1, I wrote about the enormous scale of a galactic empire.  If we’re going to turn that empire […]

  9. […] part 1, I described the enormous scale of a galactic empire.  In part 2, I discussed the economic impact […]

  10. If you are still looking for series with huge scale empires, I have some recommendations:
    Perhaps the best is the Warhammer 40k universe. It has one of the most expansive lore back stories in all SF. I would especially recommend the Horus Heresy series but it is not for the faint of heart as that series alone has 40 books and counting and there are well over 100 boos written on the universe overall. If you want to get into the universe, I recommend watching some youtube videos first. The ones I would recommend watching some of the videos by Lutin beginning with this:

    and his follow up video and his video on the Necrons and Eldar. If you want more, Arch Warhammer has an even more expansive set of videos on the subject though many of those are very technical in subject matter.

    I would also recommend the Exodus: Empires at War series which involves a massive galaxy spanning war told from a high up enough perspective to make it intelligible.

    1. I’ve had several Warhammer 40K recommendations, but haven’t gotten to the books yet. I will eventually!

  11. […] part 1, I described the enormous scale of a galactic empire.  In part 2, I discussed the impact of FTL […]

  12. […] recently posted several articles about using a galactic empire as a story setting, and now it’s time to go old-school.  Back in the old days, a galactic empire didn’t […]

  13. […] a set of blog posts over at Planetary Defense Command was brought to my attention, and before I knew it I’d read […]

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