# Where Does Space End? It Must End Somewhere!

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Then does it not follow that under such conditions, conservation laws will only restrict the manner in which time travel is employed, and not prevent it completely?

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Then does it not follow that under such conditions, conservation laws will only restrict the manner in which time travel is employed, and not prevent it completely?

What do you mean?

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Conservation of energy doesn't give two hoots if my time machine is over there by the window, or parked outside on the drive.

If "where" my time machine is located does not matter in terms of conservation, why should "when"?

As long as the object being displaced exists for the same total period that it would have done without displacement, I don't see a requirement for a contiguous presence in spacetime.

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As long as the object being displaced exists for the same total period that it would have done without displacement' date=' I don't see a requirement for a contiguous presence in spacetime.[/quote']

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Yes, briefly. It's not something you see coming up very often though.

If there is a requirement that works against it, I've not heard of it. But I'd certainly be interested.

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every direction you go you will find that space ends that way space has a shape

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every direction you go you will find that space ends that way space has a shape

like four walls of a box or house you mean?but there is space beyond that

Space is needed for everything to exist,so one would have to ask the question.What is beyond space and the first thing that existed.Nothing?

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Physical space is abstract and depends on the absolute. If one removes the absolute, then there is no physical space.

Gottfried Leibniz (Sir Isaac's nemesis) rejected the physical existence of space, absolute or otherwise. I believe he was correct. Only the absolute is physical (matter and energy), the relative is abstract (only in our head).

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Space is flat, therefore it has to end! That logic worked great in the past

Although it's looking more and more like space actually is flat, but obviously we can't prove that definitively yet

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I hate these time travel arguments.

To simply say that time travel is impossible because paradoxs are impossible is a rather childish way of looking at things. There are way to many things we dont know, like causality, how time travel would actually work, how time actually works.

To simply say that paradoxs are impossible when we dont even know if time travel is possible doesn't make sense. Until we get a much much greater understanding of how these things actually work, you can't say time travel is possible or impossible, its all just a blind shot in the dark.

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If you walk around the Earth, do you find the end? But the Earth's surface isn't infinite. You just have to expand your thinking one more dimension to apply that concept to the universe.

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If you walk around the Earth, do you find the end? But the Earth's surface isn't infinite. You just have to expand your thinking one more dimension to apply that concept to the universe.

That is not a good analogy, because the data implies that you will not come back to the same place if you travel in a straight line across the universe for long enough.

Actually, whether or not the universe is infinite is another unscientific question (this site seems to like these) since it is untestable. the best you can ever do it say that it is bigger than the the size probed so far. This isn't just pedantry; since there was probably a period of inflation at some point, our past light-cone is not the whole universe, so there are part of the universe with which we can never come back into causal contact with. Ergo, we can never see the whole universe to know how big it is (even if it were finite).

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I cant think of a way that it would or wouldnt end. i guess it would have to end somewere.

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As long as there is a universe, more could be made? I'm unsure because new matter isn't being created like it was shortly after the big bang.

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I'm not even sure the universe had a beginning. The origin of the CMBR is not completely understood. It could be that there was no beginning and no end.

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I think the Big Bang theory is fairly well supported. Objects are red-shifting. In reverse, they'd be blue-shifting and ultimately would (theoretically) for a singularity?

The big question is what came before that? But, obviously, we don't know.

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we just need to carbon date some black matter

j/k

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I believe that the universe is 4D. For instance if you could bring a 2D person to Earth their 2D brains would not understand the concept of 3D objects and would not see the 3D universe in the first place. This is like us 3D humans, we are unable to understand the concept that the universe has a 'Fourth' dimension. dark matter could also be 4D as it cannot be see or detected by anything 3D but we know that it has a fundamental part in the creation of the universe

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erm, it IS 4D. You mean 4 Spacial Dimentions, however if that were true then the 4D stuff would be able to leave this universe.

Let me explain that, thing of 2D drawing, how can you leave that univers (paper), well stand, up, gaining a verticle dimention, hence becoming 3D, similiarly the same applies for 1D "line universes"

btw what is the plural of universe?

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I dont know if this has been said before, so if it has, sorry.

but one theory is that it does end, and where it ends, it begins on the other side. (similar to that video game, where if you go off screen, you return on the opposite side, going in the same direction)

so yeah, that way, it can end, but if you go too far, you will end up on the other side, which would make it infinite, in a confined space.

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I have always understood the universe as having boundrys where space time is bent into a higher dimension. For example it would be like 2 dimsional beings on a piece of paper that had been bent into a sphere tring to escape off the edge. Any one else heard that theory, i think it was mitchio kaku who said it.

Also someone pointed out that if the universe was infintite and had been there for ever, when we looked at the sky it would constantly be lit up from the infinate amount of light from the infinate amount of stars.

Sorry hope this hasn't been said already.

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Let me succinct what the space is all about. Space is like a big image of mathematical properties. Therefore the distance of voidiness is infinity as in $\infty$!!

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I must apologise if someone has already said this but I only got up to page four. Ok how about this for a model of the universe, it is a sphere with an expanding radius. We all exist on the surface of the sphere sort of like spacetime only curved not flat.

`Scott

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Our universe(space-time) is like a balloon.We live on its surface.So even though it is finite,it never ends.One can go around and around forever and it never ends.

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Well!I am sorry.i just read the last post,its same.So my reply makes no sense.

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