# Is the Universe infinite? Is it a sphere?

I know that Scientists don't exactly know if it is infinite, and they don't think it is sphere either. But doesn't it have to be one or the other?

If it is not a sphere, is this good evidence that it is in fact infinite?

The reason I say that it would have to be one or the other is because if the Universe was not infinite, and at the same time had little to no curvature (not a sphere), wouldn't that mean you would eventually hit a wall? I would expect for the point that the Universe is expanding faster than anyone could ever travel would be made here but just because we cannot reach the edge of the Universe, doesn't mean it doesn't exist.

### 9 Answers

- jeffdanielkLv 41 month ago
We don't know if the universe is finite or infinite. If it is finite, it can not have edges, so it could be the 3 dimensional surface of a 4 dimensional hypersphere. If so, it's circumference is so large that we can not detect its curvature or see all the way around it.

There are also other possible topologies. It could be finite and unbounded but not curved. This is a torus. It is like a video game where a character goes off the top of the screen and reappears on the bottom.

- R RLv 41 month ago
Right now we have been able to see until the end of the visible universe, with microwave light. It looks like a sphere, now. The fact that it looks like a sphere does not mean its a sphere, it just means that we can see in every direction as far as your measurement devices and the speed of light allows us to see. Here is a cool YouTube Video that can help with that. https://www.youtube.com/watch?v=Iy7NzjCmUf0

&t=141s

- tham153Lv 71 month ago
Scientists have known for two centuries since Heinrich Wilhelm Olbers published that the universe cannot be infinite.

- HoarsemanLv 41 month ago
The universe appears to be (geometrically) flat ,and that, to all intents and purposes, includes a sphere with an "infinite" radius(meaning so large we cannot detect the difference )

Either way , that means we live either ,in a truly infinite universe -- make what you will of that -- or a finite one with a "boundary" of some kind -- make what you will of that .

The rest is argument .

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- ANDYLv 51 month ago
I do not know why there is a problematic situation as to whether the universe is flat or a sphere. The Hubble Space Telescope has demonstrated that galaxies exist everywhere. So I would exclude the universe to be "flat".

This will give us a meditative conclusion that the universe then could be infinite.

And as for infinity, this terminology can be expressed in two ways: The universe is so vast that we conclude it has an infinite "structure" (with a beginning and an end). Finite, here, would refer to a universe not so vast after all; and this is not our intention.

Or, the universe is infinite, that is, It has neither a beginning nor an end. And here is where our minds start to go haywire: The word "infinity", on the whole, is something that we humans can not really, and actively, explain. The word infinity (boundless) was coined in 1655 by an English mathematician called John Wallis.

- 1 month ago
As far as anyone can tell the universe just goes off into the infinite distance. However, there are limits to how far we can see objects, no matter how powerful our instruments. This is because the universe is undergoing an apparent expansion per unit volume, which means the further we look the faster things appear to recede from us. At some distance they will appear to recede at the speed of light at which point nothing beyond can ever be seen.

Unless you are an enthusiastic mathematician or a professional cosmologist, there is no need to get mixed up in the sphere versus flat argument, especially when there is no evidence to support the notion of the universe being anything but flat.

- nebLv 71 month ago
Evidence points to a ‘flat’ (zero curvature) universe. A universe with zero curvature and is topologically simply-connected (no holes) would be infinite. If it is infinite, shape probably doesn’t have much meaning. Maybe no shape is the way to describe it.

If the universe is finite, topologically simply-connected, and with a slight positive curvature, it will likely be symmetric and a hypersphere.

If the the universe is finite, has zero curvature, but is topologically multiply-connected (has at least one hole), it could be one of a family of shapes with zero intrinsic curvature but still finite. The simplest would be a 3-torus.

The 3-torus has the nice appeal of having zero intrinsic curvature as evidence indicates, but gets around mind boggling conceptual issues of infinity by being finite. Unfortunately there is no evidence it’s a 3-torus nor is there a compelling reason why it should be a 3-torus.

Update for OP - No, if the universe is infinite or has slight positive curvature, you will not hit a wall or any other kind of boundary. If it is flat and infinite (and simply connected), the separation between points must be unbounded according to general relativity. If has positive curvature, there is a bound to the maximum separation between points, but you are still confined to the 4 dimensions of spacetime metric defined in general relativity (like being confined to the surface of a sphere.

- CarolOklaLv 71 month ago
Why does it HAVE to to be one For the other. Why Can't the Universe be any shape or different shapes at different times. The Universe may have more than the 3 spatial and 1 temporal dimensions we are familiar with. There is more than one type of geometry.