# Does the universe have "walls"

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A lot of people think that the universe is infinite. But, it isn't, is it? If you asked most people that if you could get in a spaceship and go to the end of space what would be there, they would say "more space." But is this true?

What a lot of people don't know is that the big bang didn't just "create" all the matter and energy in the universe. It created space itself. That there was no space around the singularity before the big bang. Though, I'm not sure how we discovered this/what evidence there is to support it. But, assuming this is true, and that space is still expanding per the big bang (as it is still in progress) if you go in any direction eventually they'll be a point where you can't go any further, because space has not yet expanded that far yet. You hit a wall, so to speak. So, we could think of the universe as a expanding sphere. Actually, I wonder if we'll even have telescopes eventually powerful enough to see the edges of space- to see out to the point where space is still expanding, and thus we couldn't see any farther.

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It is unknown whether the universe is finite or infinite. The observable universe is finite, constrained by the speed of light and the expansion. If the universe is finite it will have some closed shape, like the 2D surface of a sphere has no start or end.

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If the universe is finite, then it is not sphere, or any other 3D shape. A sphere has an inside and an outside, and the universe has no outside. It has no edges, and no center.

Probably the simplest way to imagine a finite volume without edges would be to imagine it as "folded back on itself." What this means is that if you go far enough in one direction, you end up back where you started. Peer some unimaginably large distance and see not a wall but the back of your own head. Think of it like the game Asteroids - wander off one edge of the screen, and come out on the other side. (The real life geometry would be more complicated than that, but it is an example of a finite space without edges.)

Basically, you have to stop trying to imagine what it would look like from the outside, because that perspective makes no sense. There is no outside. It is, however, perfectly intelligible from the inside, and it's perfectly intelligible mathematically.

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Also, shouldn't be see a greater density of stars/planets/matter in one direction, which would be where the big bang originated, where it started?

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Also, shouldn't be see a greater density of stars/planets/matter in one direction, which would be where the big bang originated, where it started?

The Big Bang happened everywhere, so there is no point of origin.

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The Big Bang happened everywhere, so there is no point of origin.

OUR Big Bang only happened in our local region. There could easily be an infinite number of Big Bangs separated by distances so VAST that it makes the size of our observable universe look tiny. By "everywhere" you only mean the observable universe. Beyond that, all bets are off.

Also, shouldn't be see a greater density of stars/planets/matter in one direction, which would be where the big bang originated, where it started?

You are under the misconception that the Big Bang was like an ordinary explosion we can witness here on Earth. "Big Bang" is a misnomer. The reality is only an extremely uniform expansion, that perhaps experienced "cosmic inflation" or faster than light expansion.

Edited by Airbrush

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OUR Big Bang only happened in our local region. There could easily be an infinite number of Big Bangs separated by distances so VAST that it makes the size of our observable universe look tiny. By "everywhere" you only mean the observable universe. Beyond that, all bets are off.

Source?

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Source?

Common sense. At first Earth was the center of the universe. Then the Milky Way was the entire universe, or "everything".

Now the observable universe is supposedly "everything"? I think not.

Infinity must exist.

Edited by Airbrush

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I see. From what you suggest, it sounds like you're thinking of the observable universe as a bubble of stuff inside a larger, empty volume. That isn't an accurate picture. The observable universe is just as far as we can see, as permitted by cosmic expansion and the speed of light.

The universe, however, that thing for which the big bang was the beginning, is not a bubble. It is not any 3D shape, and so it makes no sense to refer to "beyond" it. The big bang was not a giant explosion. It was not in any location - even a very large location. It is where locations come from.

It is not analogous to thinking the galaxy is all that exists, because the galaxy is a 3D shape with an inside and an outside (even if you thought there was nothing outside, but just empty space). The universe is not an object.

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A lot of people think that the universe is infinite. But, it isn't, is it?

What a lot of people don't know is that the big bang didn't just "create" all the matter and energy in the universe. It created space itself. That there was no space around the singularity before the big bang. Though, I'm not sure how we discovered this/what evidence there is to support it.

There is no telling if the universe is infinite or finite beyond the observable universe.

There is no telling, nor will there ever be, what existed prior to the Big Bang, because it obliterated all traces of what pre-existed it. Our Big Bang (as distinct from other possible BBs consistent with the Type I Parallel Universe theory) created our region of space-time. Space existed prior to the BB. With the introduction of matter, space became space-time. This is not based upon evidence, only on logic.

Edited by Airbrush

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Space existed before Big Bang and time introduced after BB. At a moment, it makes sense but does it really? Basically I have two question based on each other--

1. Is space inside of Object (universe) ?

2. Is Object inside Space ?

Lest take an example - a watch inside a box(there is apace between watch and box). Box inside a room (there a space between box and room)............

watch --> space --> box --> space --> room --> space ----????? --> universe end ?

* so, is the edge of universe is space or made of an Object which surrounds the universe. Most probably end of universe is nothing since there is a many (infinite) ends of universe like center of universe. In my case the watch was centered but in next case a fan could be center. So we do not have a center or origin point of universe then how could we have end.

* It could be the case that universe starts with watch kept in left hand of yours and and ends at fan just above of your head.

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A wall of the universe would be like a one-sided coin. I don't see how that's possible.

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A wall of the universe would be like a one-sided coin. I don't see how that's possible.

Correct, 2D can be fit within 3D but not vice-versa.

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If the universe is finite, then it is not sphere, or any other 3D shape.

Sorry Sisyphus, but this is wrong, a finite Universe is simply static, you can use a spherical metric to describe a finite Universe....(plus (and I know you know this) a sphere is 2D, perhaps you're referring to a 3 sphere, but I don't see the relevance)

There is no telling if the universe is infinite or finite beyond the observable universe.

The topology of the Universe is around the Hubble volume, i.e there maybe clues to a wrap-around by probing the CMB, (there are no hints of a complex topology, so it's at or around the Hubble volume) so I have no idea what you mean by this.

There is no telling, nor will there ever be, what existed prior to the Big Bang, because it obliterated all traces of what pre-existed it.

Our Big Bang (as distinct from other possible BBs consistent with the Type I Parallel Universe theory) created our region of space-time. Space existed prior to the BB. With the introduction of matter, space became space-time. This is not based upon evidence, only on logic.

What do you mean by 'our' big bang, the rest appears to be unmitigated tripe.

Edited by Royston

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The topology of the Universe is around the Hubble volume, i.e there maybe clues to a wrap-around by probing the CMB, (there are no hints of a complex topology, so it's at or around the Hubble volume) so I have no idea what you mean by this.

What do you mean by 'our' big bang, the rest appears to be unmitigated tripe.

So is the universe finite or infinite? Open or closed? Bounded or unbounded?

"OUR" big bang is all we know about. There could be other phenomena like big bangs across infinite space, if space is infinite. What we can see only tells us about our region of the universe (or multiverse).

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It is unknown whether the universe is finite or infinite. The observable universe is finite, constrained by the speed of light and the expansion. If the universe is finite it will have some closed shape, like the 2D surface of a sphere has no start or end.

Thats why we cant reach the end. Because it has end points.

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