There is a possibility for our universe to be the surface volume of a (higher-dimensional) hyperspace. So if this possibility is true,then is there also a possibility that the other galaxies we see are our own galaxy after light has completed revolution around the three dimensional boundary (surface volume).

Know that we see different shapes for different galaxies.This can be perhaps due to other reasons like-

  1. distance light travelled,

  2. the angle through which we look to see the other galaxy (possibly Milky Way) after it made any number of revolutions,

  3. the part of the other galaxy (possibly Milky Way) which we see,and

  4. some other properties of light and space.

Only our Milky Way galaxy is just one possibility

Another possibilities are the number of galaxies are far less than we see because we see the same galaxy several times due to curved space.

Any possibilities for the above statements to be true?

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    $\begingroup$ There is a possibility for our universe to be the surface volume of a hyperspace. Says who? Also, look at images of galaxies. There's no way they're all the same. $\endgroup$ – HDE 226868 Mar 2 '15 at 19:37
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    $\begingroup$ Non-mainstream? $\endgroup$ – Sean Mar 2 '15 at 19:39
  • $\begingroup$ @Sean No, I'm writing an answer. Plus we can analyze this in the context of mainstream physics. Meta post indicates that is allowed $\endgroup$ – Jim Mar 2 '15 at 19:40
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    $\begingroup$ This Wikipedia page might be useful for reading. $\endgroup$ – Kyle Kanos Mar 2 '15 at 19:57
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    $\begingroup$ I don't see how living on the 3dimensional surface of a hyperphere or hyperdonut would lead to conclusions like this that other galaxies are our milky way. You might see old images of our own galaxy in all different directions then, but this would be far behind other galaxies. $\endgroup$ – Yukterez Mar 2 '15 at 19:57

No, it's not possible. The other galaxies we see are to radically different. Additionally, if we are the surface volume of hyperspace, then the universe should be closed. Our best estimates and observations indicate it's flat. Let me address both of these in more detail.

As for the other galaxies. First of all, there's the Andromeda galaxy. That is a galaxy that is bigger than ours (has more mass) and is very close. In fact, we know the Andromeda galaxy will collide with the Milky Way at some point in the future. To continue off all of this, when we look out, we can see clusters of galaxies where the angular separation between two galaxies is minimal and the physical distance we measure is relatively small, yet they appear radically different. On top of that, there are galactic mergers and collisions of galaxies that we can observe. If all are just images of the Milky Way, we'd never see two galaxies collide, yet things like the Mice galaxies show that they do.

Let's also consider that the Milky Way has its own satellite galaxies that are very clearly not images of the Milky Way.

But on to the issue of spatial curvature. If, say, the universe was a hypersphere and we were in the surface volume, the universe would be considered closed (a curvature term). In the case of such curvature, some things would be evident that clearly aren't. Consider simply geometry. On a flat piece of paper, draw a triangle. The angles inside it always sum to $180^\circ$. Now consider a sphere. Draw a triangle on the surface. Any triangle that covers a significant portion of the surface does not have angles that sum to $180^\circ$. The same would be true for the surface of a hypersphere. And since you propose the light would travel all the way around, that is significant enough for these effects to be measurable.

Now, it's possible that we are on the surface of a hyperspace, however it would have to be large enough that the curvature within our visible portion of the universe is nearly zero. That means it would be too large for light to travel all the way around and come back to us.

Furthermore, if the other galaxies we see are just images of the Milky Way, why don't we see more of them? Our galaxy radiates light in all directions. It stands to reason that if some light is bent back towards us, this would be a continuous phenomenon. So we should see light from our galaxy coming back from all directions, not just specific enough ones to make an image of the Milky Way.

Believe it or not, I could go on, but I think you get the idea that the other galaxies we see are definitely other galaxies.

  • $\begingroup$ Not suggesting that the OP's proposal is accurate, but for the sake of argument on your point of spatial curvature. They've done studies that if you wear goggles that invert your vision for sufficient time, you eventually interpret that inverted vision correctly in your mind, allowing you to see things right-side up. Now if we were all wearing fish-eye goggles from birth, you'd measure the angles of the same triangle you've seen all your life and find they add up to 180. How could you not? The world is distorted, not just the angles of a triangle. $\endgroup$ – Neil Mar 2 '16 at 15:53

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