I come out of hyperdrive as far as possible from any galaxy. How isolated am I and what do I see?

My purpose is to carry out a top-secret experiment where space is as flat as possible. For this reason I want to be maximally distant from any large masses including galaxies.

  1. In our known universe, what is the furthest I could get from any galaxy?

  2. Having arrived, what will I see with the naked eye? My guess is that I will see only galaxies and will not be able to distinguish individual stars. Will these galaxies be evenly distributed in all directions? Will I detect any galactic spirals, or will they just be dots of light?


  1. I am not looking for coordinates relative to the Milky Way. I simply want a reasonable estimate of the largest distance in light-years that would be possible from anything.

  2. Assume that there are no rogue stars in deep space between galaxies.

  3. Assume that I have excellent natural human vision.

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    $\begingroup$ When you say "detect" or "see", are you talking about using the naked eye, or telescopes? The Hubble Deep Field, for example, was able to image the shapes of galaxies from many billions of lightyears away, much farther than the diameters of even the largest known voids. $\endgroup$
    – parasoup
    Feb 22, 2021 at 0:23
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    $\begingroup$ I presume what you would see with your naked eye would be the bulkhead of the ship you are in. That presumes that you can see at all. What you see would depend a lot on exactly how you got to where you are. $\endgroup$ Feb 22, 2021 at 2:40
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    $\begingroup$ Why not ask this in astronomy.SE ? You might reword to simply "what is the largest known volume which contains no galaxies" and then place yourself in the middle of that. $\endgroup$ Feb 22, 2021 at 19:30
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    $\begingroup$ Could it be that the gravity influence by your own ship curbs the space more than any nearby galaxy would? $\endgroup$ Feb 22, 2021 at 20:23
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    $\begingroup$ @DrMcCleod - P.S. Are you saying that space is flat within any spherical container? I could simply use the inside of an evacuated steel ball if that were the case. I don't think so! $\endgroup$ Feb 22, 2021 at 23:04

3 Answers 3


Possibly $\sim$50 million light-years

I agree with the broader point in Ash's answer, if not the specifics. Cosmic voids are structures on the order of tens of millions to possible billions of light-years across. In general, they have low densities, roughly $\sim$10% of the mean density in the universe. That said, many voids do contain galaxies, albeit fairly isolated ones. Pisces A and Pisces B are notable nearby examples, although given the large distances to voids, detecting void galaxies is not an easy task. That said, their very existence means that your problem is a bit more complicated than just finding the maximum size of a void.

The spiral galaxy MCG+01-02-015 is sometimes cited as being the most isolated galaxy in the universe. Lying roughly 300 million light-years away, it sits near the middle of a void about 200 million light-years across. As far as I can tell, no other galaxies have been found within that void, although it's possible that there are low-surface brightness galaxies in the vicinity, or perhaps extremely dim dwarf galaxies.

There are larger voids than the one that hosts MCG+01-02-015, but most are farther away, making it even harder to probe them. For example, the supervoid Ash mentions is centered at a redshift $z\simeq0.22$, which corresponds to a distance of roughly 3 billion light-years, ten times as far away. Therefore, any source would be 100 times dimmer, making it harder to detect any galaxies that might lie within it!

The point is, current observational evidence says that you could come out of hyperspace 50 million light-years away from the nearest galaxy - a factor of ~20 lower than if we were to consider that supervoid. This would place you halfway between MCF+01-02-015 and the edge of its host void. At that distance, with the naked eye, you'd see . . . nothing. I believe Triangulum and Andromeda are the only galaxies visible to the naked eye from the Milky Way, and they're a mere 2 million light-years from us.

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    $\begingroup$ Arent most Galaxies hard to see due to the light of our own Galaxy obscuring the light of those other Galaxies? Its like trying to see a candle in the dark while a floodlight is shining in your face. So at 50 million lightyears with no other lightsources, what would you see? $\endgroup$
    – Demigan
    Feb 22, 2021 at 14:25
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    $\begingroup$ @Demigan: Even without other light sources, there's a limit to the sensitivity of the human eye; at some point, there's simply not enough photons to trigger the rods in the retina. In astronomical terms, objects with magnitude 8 are possibly viewable with the naked eye under optimal conditions. But an object with a given brightness will decrease by 5 magnitudes if it's moved 10 times farther away, and Andromeda is magnitude 3.4 at a distance of 2 Mly. So at 50 Mly, Andromeda would be about magnitude 10.3 — not visible without a telescope. $\endgroup$ Feb 22, 2021 at 16:44
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    $\begingroup$ @MichaelSeifert that is a good answer but it still misses that one thing: at what distance would Andromeda be visible with the naked eye if our Galaxy's own light wouldnt obscure it? I have no problem believing it can't be seen at that distance, but I would like to see the actual distance as proof that yes, it is too far. $\endgroup$
    – Demigan
    Feb 22, 2021 at 18:41
  • $\begingroup$ @Demigan: Given the rules above, Andromeda would drop below the limit of human visibility once it got about 5 magnitudes dimmer, which would mean it would need to be 10 times farther away, or about 20 Mly. $\endgroup$ Feb 22, 2021 at 18:42
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    $\begingroup$ Bode's Galaxy (12 Mly) is borderline visible on Earth; the Pinwheel Galaxy (20 Mly) is likely to be visible against a truly black background. Still not sufficient to see anything if you're in the middle of a cosmic void. $\endgroup$
    – Mark
    Feb 22, 2021 at 22:00

The supervoid sounds pretty promising

There's a 1.8 billion light-year across feature called the supervoid. It's about 3 billion light-years away from Earth, and averages 5 protons per cubic meter.

I have no idea what it will look like to the naked eye. If I had to guess: Probably billions of tiny fine pinpricks of light that you can only see if looking directly at them, but are basically invisible in your peripheral vision, with the variation in brightness so subtle it would be difficult to spot any features.

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    $\begingroup$ This answer isn't necessarily correct; the void you mention is large but almost certainly contains galaxies and other structures within it. "Void" is a relative term; heck, our galaxy exists inside what is technically a void. $\endgroup$
    – HDE 226868
    Feb 22, 2021 at 0:30
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    $\begingroup$ @HDE226868 you dispute the existence of thing like the Boötes Supervoid? $\endgroup$
    – PcMan
    Feb 22, 2021 at 1:12
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    $\begingroup$ @PcMan Of course not. That's definitely not up for debate. But it contains galaxies - a glance at Wikipedia estimates that there are ~2000 galaxies in that void. That's really my point; you have to look not just for voids but for voids which contain no (or just a handful of) galaxies. I agree that a void is a good choice, but for a reasonable distance estimate, you need to look further than just its size. $\endgroup$
    – HDE 226868
    Feb 22, 2021 at 1:14
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    $\begingroup$ Peripheral vision is more sensitive than direct vision in conditions of low light. Sometimes you can only see a star by looking a little off to the side -- try it the next time you're under a starry sky! $\endgroup$
    – TonyK
    Feb 22, 2021 at 14:10
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    $\begingroup$ Not necessarily the corner of your eyes, more a little off-centre. The fovea is jam-packed with colour-sensitive cone cells, leaving little room for night-sensitive rod cells. $\endgroup$
    – TonyK
    Feb 22, 2021 at 14:15

The Cosmological Horizon

People, of the superstitious sort, used to think that the world was flattish and that, at the horizon, the world ended, and there was a great waterfall and if you sailed over it, you'd die.

Well, eventually. For a little while, at least, you'd have a really good view of some really big oliphants before crashing into the bitter cold carapace of a gigantic turtle.

Obviously, we know different, because some fellow called Magellan decided to sail towards the horizon and prove them wrong, which he did.

But that's just one little planet. The universe itself is much bigger and has more surprises in store.

For example, we really don't know how big it actually is. We only know how far in time we can see using our best technology. But you've got a starship that can take you to any point --- and that means you can truly get away from it all!

And to boot, you can prove Magellan, ultimately & fundamentally, wrong.

Eventually, your starship is going to approach not just the edge of the Geocentric Observable Universe, but you're going to approach the edge of the Universe proper. There will be, beyond this line, no stars, no planets, no comets, no cupids, no galaxies, no black holes, white holes or blue holes. Only radiation & the information it carries with it. This is the Cosmological Girdle, a sort of hazy & dim region of sparse particles of energy.

But beyond even this region, your starship will approach the very edge of Absolutely Everything Whatsoever, which is the Cosmological Horizon. The horizon, on Earth, we know, is the demarcation line where the light of the Sun first peeks up over the arcking edge of the Earth.

The Cosmological Horizon is the ever advancing demarcation line between that place where you can discern the allermost, uttermost and lastestmost squimon of information originating from within the Universe itself on the one hand, and that other place where you can no longer discern anything at all from within the Universe. Could be a light particle or some bit of matter or radiation, doesn't matter. Once your starship reaches that ultima thule of cosmology, you can pull up alongside the speeding squimon and stand on the theoretical border between The Universe, towards the aft of your ship, and Not The Universe, towards the bow.

Detectors arrayed along the aft quarters of your ship might detect 1 or 2 particles of energy in a petrasqintijillion cubic parsecs of space, the dim glow of the Universe's bow wave. Detectors arrayed along the bow of the ship can detect nothing approaching from ahead, and will also be unable to detect anything approaching from abaft. You've just passed beyond the last anything of the universe.

So, just bop along for a few more lightyears (ha-ha! -- how can there even bé a lightyear where there is no light?) and come to a full stop.

At this point, distance ahead is meaningless, because there's nothing around you to compare with. You are now in THE VOID. No rinkydink intrauniversal void this! This is the place everything that the Universe actually is expands into and illumines with its radiance.

Looking out your windows, you will be able to see only these two things:

  1. NOTHING --- Nothing to see here, folks! You are beyond the physical & astronomical extent of the Universe, so there are no stars or galaxies here. You are now beyond even the radiation emanating from the objects that are along the outermost edge of the Universe. In every direction you look with your eyes, point a telescope or aim any kind of radiation sensor, you will receive no inbound data.
  2. EVERYTHING --- Curiously enough, having left the final frontier outpost of the Universe, you will interestingly and conversely enough, be able to see everything! Every particle of matter and every particle of radiation that exists is now located within your starship, or radiating from it, whether it's your blinking hazard lights or the residual emanations from you hyperdrive exhaust ports. If you sent out a probe from your vessel, it would be surrounded & bathed in the very dim radiation of your own private little universe.

Of Note: You specified the "known universe", so here's something to chew on. Wherever you are, you are at the centre of the Observable Universe. If you move ten billion lightyears away from Earth, the centre of the O.U. moves ten billion lightyears away from where it was before, and naturally the Known Universe grows along with it.

There is also the Unobservable Universe out there, beyond what we can detect. This is where your starship is now. But, paradoxically enough, now that you have actually reached the edge of the U.U., and have gone beyond it by some distance, you have actually not only increased the size of the O.U. by orders of magnitude, but you have also taken the Known Universe with you, out beyond itself. Kudos and welcome to the Twilight Zone!

I've read that the U.U. may be 23 trillion lightyears in diameter. I would take that to mean everything up to the Cosmological Horizon. I've also read that the Universe is about 13.8 billion years old. Since we really don't know where we are within that 23 trillion lightyear diameter volume, and thus don't know which direction the original centre is (where the Singularity was), it will be a matter of pure guessing as to which direction to fly towards. If we happen to be only 14.2 billion lightyears from the Edge of the Universe Proper, and the shortest direction is "down" from the solar system, then you'll only be travelling something like 28.5 billion lightyears to get beyond the Cosmological Horizon.

If you choose wrong, well, you're going to be travelling a long, looooong way! 13.8 billion lightyears beyond the 23 trillion light years to travel through Absolutely Everything.

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    $\begingroup$ I would expect that the universe, being isotropic, would look much the same from anywhere. $\endgroup$ Feb 22, 2021 at 4:55
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    $\begingroup$ I agree with @TheSquare-CubeLaw; the cosmological horizon is defined relative to an observer at any point in space. Different observers have different cosmological horizons - it's not a particular special location. Similar, the notion of "observable universe" is defined differently for different observers. We also don't have evidence to indicate that the universe itself is finite; I believe Planck and WMAP results are consistent with (though not restricted to) a flat, infinite universe within measurement error. $\endgroup$
    – HDE 226868
    Feb 22, 2021 at 4:57
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    $\begingroup$ Wouldn't it suck if you successfully got away from everything just to end up next to the shipyard built with the ships of all the people who had that same idea? $\endgroup$
    – nwp
    Feb 22, 2021 at 10:31
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    $\begingroup$ Please don't perpetuate the myth that people before Magellan thought the Earth was flat. $\endgroup$
    – vsz
    Feb 22, 2021 at 12:25
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    $\begingroup$ While I love this answer, the question is tagged [science-based], and so this answer doesn't belong. None of this matches our current understanding of the universe $\endgroup$
    – coagmano
    Feb 23, 2021 at 2:20

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