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I was thinking, if the universe is space and time expanding, lets say in 3D (like a sphere). And it is doing that in a constant or not constant speed, there is a debate about that, never mind that but we know the speed we know it's expanding. So what would happen if we traveled faster than the expanding universe and we reached the end? What would we see? would we be out of space/time ? Would laws of physics work outside the universe?

Qmechanic
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AlCode
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The concept of the expansion of the universe is hard to get your head around. We describe the universe is infinitely large, and it is expending into itself. So, there is no outside, You can't leave the cosmos. If you could find the edge of the universe and exit through that edge, you would re-enter the universe from the other side. Edges of the universe are linked together. Thus, you could never leave.

The theory of muulti-universes states that law of Physics would be different in another universe. String theory predicts that there are 9 spatial dimensions, so there is many ways those dimensions could be arranged.

TBBT
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  • Thank you very much for the elaboration! Need to read more about this, it's very interesting.. – AlCode May 07 '15 at 09:16
  • @TBBT Could you give some references for your claims that if you would "exit" the universe you enter it from another side? – Hrodelbert May 07 '15 at 09:37
  • The phrasing "If you could find the edge of the universe and exit through that edge, you would re-enter the universe from the other side" is a bit unfortunate, since no such edge exists. If the Universe is infinite (which it probably is), you can go on and on forever, even in a magical hyperluminous spacecraft, and keep encountering new galaxies. If the Universe is finite, you will just eventually end up where you departed from. Just like if you travel far enough on the surface of Earth, you won't reach an edge but end up back home. – pela May 07 '15 at 10:04
  • @pela i thought of the universe as infinite space without time and matter, just empty space, then after the big bang i thought that space/time/matter was created and so it would expand in all directions, so i thought you can go "outside" and watch the universe expand from a another view point. Well seems it's not possible :/ – AlCode May 07 '15 at 10:33
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    @Orom: I don't know if this is a comfort or not, but you share this notion of the Universe with probably 99.99% of anybody how has even given this a thought. The expansion of the three-dimensional space is concentually very difficult to understand without a bit a math, because we "want" it to expand "into something", which it doesn't. A popular analogy is to consider the surface of an expanding balloon, where the surface itself is the Universe, and the outside "doesn't exist", but this analogy misses some important aspects. – pela May 07 '15 at 10:55
  • @pela do you have some resources on this? would like to read more about it. not the balloon part but not expanding into anything part :D – AlCode May 07 '15 at 11:04
  • @Orom: Well, depending on your background, I'd say start with the Wiki article on the metric expansion of space. Here you'll also find plenty of references, including my former colleague Tamara's splendid article on common misconceptions about expansion, etc. The latter does require some math for understanding everything, but even without this tool, you can probably still learn a lot from it. – pela May 07 '15 at 13:06
  • Also, this previous post gave a very good summary of Tamara's article. – pela May 07 '15 at 13:07
  • If you wanna go more in-depths, I'll recommend Steven Weinberg's "Gravitation and Cosmology". You can find a crappy pdf-version here – pela May 07 '15 at 13:13
  • The latter is quite heavy, though. A better choice would possibly be Sean M. Carroll's "Spacetime and Geometry". I'm not sure you can find this online, but the underlying lecture notes are here. – pela May 07 '15 at 13:16
  • @pela damn thank you very much for this answer and those links! Im just a guy who is curious about space and physics, I'm a Computers Sci. major, so yeah, i started to get involved more in physics it seems quite interesting! thank you again! great material here! – AlCode May 08 '15 at 07:24
  • You're very welome, @Orom. – pela May 08 '15 at 08:58
  • If you could find the edge of the universe and exit through that edge, you would re-enter the universe from the other side. ––– I think this is incorrect because science says the universe is open, so exiting at one side will not make you enter on the other side. – Duck Nov 12 '17 at 17:16