In Isaac Asimov's Robot/Empire/Foundation series, humans, during their second colonization wave, settled (probably) all the inhabitable worlds in the Galaxy, but no more. They did not, as far as I can recall, make any attempts at colonizing other galaxies, at least not before the fall of the Empire.

I remember reading in one of the books that hyper-stellar travel allowed humans to go reach even beyond the borders of the Milky Way, but I cannot recall them doing so or any reason not to.

Did they, then, try to go beyond the Milky Way and I don't remember? If so, why didn't they settle any extra-galactic planets? Or if they really didn't try, why not?

I am referring to the extended Asimov universe (including the post-Asimov Second Foundation trilogy: Foundation's Fear, Foundation and Chaos, Foundation's Triumph).

  • 1
    The Andromeda Galaxy is 2.5 million light-years away - even at 1000 times the speed of light, that's 2500 years to get there. I don't recall the limits of the Jump Drive in Foundation... Jun 25, 2014 at 15:09
  • 1
    Our own galaxy is about 120,000 ly in diameter, and the Galactic Empire seems to have been a pretty cohesive civilization, so I doubt it took 120 years to travel from one end of it to the other. But as I say in my answer, intergalactic distance is likely to be the key problem. Jun 25, 2014 at 15:18

6 Answers 6


In Foundation and Earth, Golan Trevize states that there is an issue with attempting intergalactic travel. He mentions in particular that all attempts to travel even between the Milky Way and our closest galactic neighbour (the two Magellanic Clouds) have met with total failure.

He posits that a race that has completely dominated their own galaxy may have sufficient resources and time to overcome the, evidently very significant technological difficulties of travelling between galaxies.

Additionally, the Jump-Drive technology that allows instantaneous transit between any place within the galaxy doesn't appear to work extra-galactically. The implication is that while the Jump Drive can allow you to travel to anywhere within the galaxy instantly, traveling outside the galaxy requires you to either take a blind jump (which invariably ends in death) or travel in normal space at sublight speeds.

Trevize said, "Listen to me again. Just outside the Galaxy are the Magellanic Clouds, where no human ship has ever penetrated. Beyond that are other small galaxies, and not very far away is the giant Andromeda Galaxy, larger than our own. Beyond that are galaxies by the billions.

"Our own Galaxy has developed only one species of an intelligence great enough to develop a technological society, but what do we know of the other galaxies? Ours may be atypical. In some of the others-perhaps even in all-there may be many competing intelligent species, struggling with each other, and each incomprehensible to us. Perhaps it is their mutual struggle that preoccupies them, but what if, in some galaxy, one species gains domination over the rest and then has time to consider the possibility of penetrating other galaxies.

"Hyperspatially, the Galaxy is a point-and so is all the Universe. We have not visited any other galaxy, and, as far as we know, no intelligent species from another galaxy has ever visited us-but that state of affairs may end someday. And if the invaders come, they are bound to find ways of turning some human beings against other human beings. We have so long had only ourselves to fight that we are used to such internecine quarrels. An invader that finds us divided against ourselves will dominate us all, or destroy us all.

Trevize seems to be saying there is no theoretical upper limit on jump distance, but in practice the range of human jump technology is limited. We don't know if this is because of energy requirements, difficulty of navigation, or something else.

In terms of scale our own galaxy, the Milky Way, is about 120,000 light years in diameter. The Magellanic Clouds are about 150,000 light years away. (If humans never reached the Clouds, it implies the range of human ships was not sufficient to cross the Milky Way in a single jump.)

The nearest other major galaxy is Andromeda, which is 2.5 million light years away, more than 16 times as far as the Clouds.

  • 5
    In the short story "Escape!" Powell and Donovan are jumped right out of the galaxy by a mischievous Brain. 300,000 parsecs they went in some undisclosed direction, nearly a million lightyears. The distance gauge in the ship had markings up to a million parsecs, which makes Andromeda reachable.
    – Kyle Jones
    Jun 25, 2014 at 18:33
  • 4
    @KyleJones: I was going to mention that myself. It is possible, however, that the Brain exaggerated the distance it actually sent Donovan and Powell. It is also possible, since humans have forgotten robotic technology, they no longer have the calculating capacity required for such long jumps, which may require a positronic brain. Jun 26, 2014 at 8:52
  • 1
    I remember, that someone in the Foundation Story said, that the planets, suns and solar systems at all, they haevn't explored it and have no map of the area around the known galaxy. It is too dangerous to travel there, they fear, that they are jumping right into a sun oder on the surface of a planet.
    – souichiro
    Jun 26, 2014 at 9:13

There are certainly technological issues at work here. However, I suggest that those issues only exist because the robots have thus far suppressed any technology that would solve them.

See Richard's quote from Foundation's Edge. It speaks directly about threats from intergalactic civilizations. Also in Foundation's Edge, we learn that the robots, Daneel in particular, have been systematically manipulating humanity for tens of thousands of years. They have caused humanity to forget robotic technology, to leave Earth behind, to create the Empire and later the Foundation, and to ignore Gaia until they were ready. We can assume that the robots have been involved in many more ways as well.

We also learn that the robots are attempting to advance Gaia into Galaxia, specifically to counter possible intergalactic threats.

What would happen if humanity encountered a hostile intergalactic alien too early? The actions of a few brave explorers could potentially touch off a large-scale conflict with another galaxy. Without Galaxia, humanity may not be able to cope with this.

The robots would surely take steps to prevent this. After all, if a threat to all humanity exists, the zeroth law compels them to act. They have suppressed technology and guided human endeavors many times before. They have excellent motivation to do so here, too. They have prevented humanity for leaving the galaxy in exactly the same way they prevented most of humanity from encountering Gaia, and for exactly the same reasons.


TTBOMK Asimov did not give the reason explicitly, but let me suggest that it is because it is obvious to the psycho-historian :)

The most important economic law is that of diminishing returns. In antiquity, agriculture-based societies settled in & exploited richest lands first because they yield more crops for the same effort.

Asimov suggests that the Milky Way is far from completely explored, which is understandable as the Milky Way comprises 100 billions stars. For instance the location of Earth was forgotten.

And that's it : even if you have the technology & power to get to Andromeda, it would be economically silly to try and expand there before having exploited all possibilities in the current galaxy.

  • 1
    What you are saying is true, but I recall the number of inhabited worlds in the Milky Way remaining unchanged for at least the last hundred years before the events in "Foundation", which most likely meant the Empire had no more habitable planets to expand into. Jun 25, 2014 at 16:49
  • 5
    @RedCat23 - Or no more political will to expand.
    – Bobson
    Jun 25, 2014 at 17:55
  • @Bobson: Great point, but even if the Empire itself lacked the will, it's doubtful that no-one else tried it. Many colonisation programs on Earth were private ventures, or even conducted by rebels, like the Dutch. Jun 26, 2014 at 8:50
  • @JamesSheridan: I rather think the Giskardian robots, under the leadership of Daneel, made sure almost no one would want to. I'm referring to the techniques of planetary mind control explained in Foundation's Triumph. Jun 26, 2014 at 9:08
  • 3
    I haven't read that book. Is that one of the new post-Asimov stories? It's not exactly fair to keep that in mind when discussing why something happened in the Asimov works. Jun 26, 2014 at 10:12

To paraphrase The Hitchhiker's Guide to the Galaxy, space is really big, and intergalactic space is so mind-bogglingly huge you wouldn't believe it.

Our own galaxy, the Milky Way, is about 120,000 light years in diameter.

The nearest other major galaxy is Andromeda, which is 2.5 million light years away.

IIRC Asimov was vague about the exact speed and capabilities of faster-than-light travel in the Foundation universe. But if it takes a year to cross our galaxy, it would take more than 20 years to reach Andromeda.

It may be that this was just too far to make a serious attempt at settling Andromeda. In particular, it could be beyond the range of human spacecraft -- intergalactic space is very, very empty, and it is unlikely there would be any opportunity to refuel during the 20 year voyage.

  • 1
    Re: "IIRC Asimov was vague about the exact speed and capabilities of faster-than-light travel in the Foundation universe": Dunno about capabilities, but he was actually astoundingly precise about its speed. Just a few pages into Foundation (page 4 in my copy), we learn that "Through hyper-space, that unimaginable region that was neither space nor time, matter nor energy, something nor nothing, one could traverse the length of the Galaxy in the interval between two neighboring instants of time." So no, it doesn't take a year to cross our Galaxy.
    – ruakh
    Jun 26, 2014 at 5:38
  • @ruakh: Fair enough. But range could still be a limitation. Also, the jump through hyperspace may be instantaneous, but if you need to stop and recharge, do navigational calculations, or whatever between jumps, your effective speed is not infinite. Jun 26, 2014 at 8:16

Asimov's Jump Drive did not jump particularly far in a single jump. Ships traveled long distances by doing one jump, calculating the next and rejumping. As others said, apparently this was quick enough in the Milky Way to keep a cohesive society together.

But ships, even Military ones, couldn't jump anywhere or any distance. That's how Bel Riose could do his methodical attack on the Foundation by occupying key sites that the Foundation couldn't take. If the Foundation fleet could just jump to Trantor and nuke it, this campaign could make no sense. The most likely reason is that ships need to refuel and reload consumables like air frequently at known worlds, so if Riose took those, the Federations would have to fight him where he was prepared for it.

So the most likely reason is that a ship to the Magellanic Clouds would have to carry all the fuel and air it would need for the trip with it, and the multiplying load is just impractical. And with a whole galaxy to fill, why bother?

  • Though you do raise a fine point, I assumed the need for multiple jumps was due to the effect of the gravitational wells of stars (mostly) affecting the jumps themselves, either at the start point, the end point or the distance in-between. Intergalactic space being empty, there is nothing to impede a jump over large distances. Am I wrong in my assumption? Jun 26, 2014 at 22:35
  • I don't know that it was ever directly stated what the calculations needed for the jump depended on. You could say that the lack of nearby marker stars would impede the jump by making it impossible to calculate your position post-jump. Even in-galaxy, the ability for a region to hold or defend a border in space requires serious restrictions on fleet mobility - how can you stop the enemy from jumping right to your homeworld?
    – Oldcat
    Jun 26, 2014 at 22:41
  • The Bel Riose Argument is convincing, and I also believe that a lack of marker stars might thwart navigation. I shall add your answer to the question summary. Jun 27, 2014 at 6:25
  • Do note that the new gravitic ships with their advanced computers where capable of much much faster consecutive jumps than their older counter parts. Jun 27, 2014 at 7:04
  • @PaulHiemstra: Indeed, but they were not available until roughly half a millennium into the Interregnum, so they couldn't have been used by the empire to expand into neighbouring galaxies. Jun 27, 2014 at 10:48

In order to Jump from point A to point B, one needs to know the coordinates of B in A's frame of reference. How do you establish that if you haven't ever Jumped to B before? You have to make an educated guess, which can be very risky.

During the early days of hyperdrive, A and B would typically be nearby stars. Educated guessing means compensating (at A) for B's proper motion in the local stellar environment, including taking into account the fact that you are seeing where B -was-, not where B -is- (Relativity). But stars in a given stellar neighborhood often move roughly in tandem, plus if B is N light-years away, B's change in position over the last N years is liable to be quite small relative to its neighbors. So short Jumps within a galaxy are liable to be easy to map out in relative safety; extend that for several thousand years with ever-increasing confidence and one can map out the galaxy very well.

Contrast this with Jumping from Milky Way to Andromeda. First one must compensate for 2.5 MILLION YEARS of relative motion. Extrapolating along a straight line will be quite error prone, both because we cannot measure the -apparent current motion- of Andromeda very accurately, and because we cannot accurately compensate for the cumulative gravitational influence of other galaxies. So our first Jump is off by some large random amount.

Now we are (unless VERY lucky) in the middle of intergalactic space, trying to correct our guess based on what we see. But where are we, exactly, relative to Andromeda? We could easily move our ship 100,000 light-years in any direction without changing the outside view, except under very precise measurements. And we WILL have to Jump to other points to be able to re-measure Andromeda's relative motion (as seen from the first destination). But how do we establish a local coordinate system with -absolutely nothing- but our ship as a nearby fixed reference?


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.