Galaxies are moving away from us proportional to the distance between us and them , but nothing can travel faster than light, so even the farmost galaxies should be travelling away from us along with the space time with a speed less than that of light. In that case is our universe finite?
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Qmechanic
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1i dont understand your question. Please make it clearer. – GRrocks Mar 29 '15 at 07:41
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3Hi you don't seem to have a particular question, rather just a statement here. It is spacetime rather than galaxies that is expanding and as far as I know there is no limit to the velocity of spacetime itself. Could you edit your post to include a question thanks – Mar 29 '15 at 07:41
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im just asking whether im right at my point of view, – Keerthi Kumaran Mar 29 '15 at 07:45
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http://en.m.wikipedia.org/wiki/Metric_expansion_of_space might help you on your post, regards – Mar 29 '15 at 07:53
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1possible duplicate of Will acceleration rate of expansion of space become faster than speed of light? – ProfRob Mar 29 '15 at 08:22
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Galaxies are not moving away from us, it is the space between us and the galaxies (and everything, in general) that is continually expanding. This is allowed to happen faster than the speed of light, because no object actually crosses the light speed barrier in the process. So consequentially, the universe has no size constraint like the one you've stated.
Hritik Narayan
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the space between us and the galaxies comprise of dark matter and as the universe expands the density of the universe gradually reduces this indicates that dark matter is moving from the confined volume to a new big volume. in that case is dark matter moving faster than light – Keerthi Kumaran Mar 29 '15 at 07:58
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I don't understand how you arrived at this conclusion. Nothing actually does move in the normal sense, the space expands, just like I said in the answer. – Hritik Narayan Mar 29 '15 at 08:00
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i said like that thinking that , this expansion is similiar to expansion of gas in which particles move outward when their volume is increased – Keerthi Kumaran Mar 29 '15 at 11:13
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i think in the way similar to the expansion of gas in which the particles moved divergingly outward when there is an expansion and i think dark matter is playing the same role in the expansion of our universe. – Keerthi Kumaran Mar 29 '15 at 11:23
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If you mean by "our universe" the matter in spacetime we are able to reach and observe then you are right. The universe will become more and more finite for us unless someone will invent a "warp drive" or "wormhole" (currently the probability for it is very low).
According to research you have ca. 100bn years time before all others galaxies will be gone beyond the cosmic light horizon. So at this time you are restricted to do your travel and oberservations within Milkdromeda.
https://en.wikipedia.org/wiki/Timeline_of_the_far_future http://arxiv.org/abs/1102.0007v2
But that does not mean that the entire universe is finite. (See comment on top)
Randy Welt
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