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My question is what and how the boundary of the universe should be like. I mean what if someone tried to pass through it. Since the universe is not expanding at the speed of light therefore we can surely catch it. What if you try to push through it. What will happen after all if someone reaches the edge of the Universe. Clearly there must be matter near it what if they move towards the boundary. And above all will laws of physics will be same there?

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    $\begingroup$ What boundary? Also, space can expand faster than light. $\endgroup$
    – ACuriousMind
    Commented Nov 12, 2016 at 16:20
  • $\begingroup$ The universe has a fixed size. And I said that it does not expand faster than light to justify that we can touch the boundary before it move farther. $\endgroup$ Commented Nov 12, 2016 at 16:22
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    $\begingroup$ Please cite where you have read that the universe has a fixed size. At this point there is really no doubt that it is expanding. $\endgroup$
    – Javier
    Commented Nov 12, 2016 at 16:26
  • $\begingroup$ There is no boundary. There is a horizon though. The term "horizon" is most appropriate: just like the horizon observed on earth, it moves along with the observer and can not be reached. $\endgroup$
    – Johannes
    Commented Nov 12, 2016 at 16:29
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    $\begingroup$ Are you aware of the balloon analogue of the universe? We are like ants on the surface of a balloon. they will never find an end of their two dimensional universe, and we cannot find an end in our three dimensional universe $\endgroup$
    – anna v
    Commented Nov 12, 2016 at 17:14

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Since the universe is not expanding at the speed of light therefore we can surely catch it. 

There is no law that says spacetime, as it is not a "thing", cannot expand at any speed, even beyond the speed of light. ACuriousMind refers to this in the comments above and the link included: Space Expansion And The Speed Of Light.

What will happen after all if someone reaches the edge of the Universe?

By definition, the universe is all there is, so there can't be a boundary in the normal sense of a boundary wall, as if there is something beyond the "wall", if should still be part of the universe. One way that might get around this is to say, or find out preferably, if the universe has positive curvature. I am wary of giving 3 D analogies, such as an ant running around the curve of a soccer ball, but there, I've just done it......damn

Clearly there must be matter near it what if they move towards the boundary. And above all will laws of physics will be same there?

Why should there be matter near it? Anyway, this is a moot point if you accept my argument that a boundary cannot exist between two parts of the one universe.

We don't have any reason to suppose the laws of physics will be different anywhere ( except in black holes), but we don't have any proof that they are the same as here. We don't know.

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