Is the universe spherical?

D

DRZion

Theoretical Experimentalist
Valued Senior Member
I'm sure that has been discussed to death. Is the universe spherical?

If the big bang started the universe, shouldn't the universe have expanded semi-uniformly across space? Since space is 3-dimensional and the expansion is uniform, the universe should be something like a big sphere with absolutely nothing outside of this sphere.
 
This idea of a sphere makes most sense in the 3D space (+time) we live in. In the other dimensions sphere is not necessarily the best solution. Actually we cannot even talk about shapes when we talk about the universe. These terms simply don't mix.
 
Large things are spherical and it is probable that the universe would have settled into the best shape gravitationally too. While the universe probably rotates too, it's sheer size makes it unlikely that it would do so at a speed where the sphere would begin to flatten out.

A 3D expansion would mean a shell of material which has expanded away from a definite centre. A 4D hypersphere best suits the big bang idea though it adds yet another problem to the beleaguered idea in that how does something expand in four physical dimensions?
 
kaneda said:
A 3D expansion would mean a shell of material which has expanded away from a definite centre. A 4D hypersphere best suits the big bang idea though it adds yet another problem to the beleaguered idea in that how does something expand in four physical dimensions?
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1. 'Beleaguered' is a rather obvious attempt at weasel words.
2. Hyperspheres are not the only closed, boundary-less n-dimensional objects. I've been over that with you before.
3. An expanding 3d object doesn't need to be embedded into a 4d space to be a valid concept. Haven't you ever done any differential geometry? Oh, of course you haven't.
 
Since the universe began as a point and expanded semi-uniformly it should end up as some kind of sphere. The idea of rotational flattening seems valid, but I don't know what would cause such rotation.

A 4-d space is just a 3-d space as seen over time.. hard to visualize, but I like to see it as a you tube video. If you drag the time slider you are manipulating the 4th dimension, time. Of course, a you tube video is only 2-d, but you get the idea...

The point is that reality is truncated. An expanding space-time is stretching reality asymetrically, meaning that the side of an object further away from the center is LARGER than the side closer to the center... right? This would have to mean that the universe is expanding ever faster, or maybe I am getting confused.
However, this 'truncated reality' is something curious.
 
DRZion said:
Since the universe began as a point and expanded semi-uniformly it should end up as some kind of sphere.
Click to expand...
Not really. If the universe were torus shaped and you 'wound time backwards' you'd find the torus shrinking to a point, just as a sphere would. The limit of shrinking anything down to zero size is a point, since a point is the only zero extension object. Various people have done work on 'topological flop transitions', in that some of the dimensions of space-time curl up very small, shrink to zero and then re-expand in a different shape. Such transitions would allow a sphere to change to a torus or a torus into a Klein bottle, anything with a topology change.
 
The torus would never actually get to a point unless it shrank below planck length, but that is an entirely different argument.

Topology flop transitions. Sounds interesting. If these mathematicians are clever enough to calculate how such a transition happen, maybe they should also try to include the probability of such transitions happening.. doesn't seem very likely that our universe is either a perfect sphere, or a perfect torus, or anything really...

However, it seems that even after such transitions there should be a center of expansion. This is important in a certain theory of mine that would contribute to the big crunch model.
 
DRZion said:
The torus would never actually get to a point unless it shrank below planck length, but that is an entirely different argument.
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Firstly, Planck lengths have nothing to do with that and secondly nothing becomes a point until it's shrank to zero size so your attempt to split hairs is wrong too.

DRZion said:
doesn't seem very likely that our universe is either a perfect sphere, or a perfect torus, or anything really...
Click to expand...
Deformations are entirely different to topological changes.


DRZion said:
However, it seems that even after such transitions there should be a center of expansion. This is important in a certain theory of mine that would contribute to the big crunch model.
Click to expand...
Something tells me your grasp of what I said is a little worse than you might like people to believe.
 
AlphaNumeric said:
1. 'Beleaguered' is a rather obvious attempt at weasel words.
2. Hyperspheres are not the only closed, boundary-less n-dimensional objects. I've been over that with you before.
3. An expanding 3d object doesn't need to be embedded into a 4d space to be a valid concept. Haven't you ever done any differential geometry? Oh, of course you haven't.
Click to expand...

1. Lots of problems with the big bang idea. Do look at something other than the wikipedia.
2. Nonsense is still nonsense, no matter how many times you repeat it. Odd shapes would lead to some very strange areas of space, which we have never detected.
3. With 3D space with everything magically moving away from everything else, a point of origin could be traced back to. Real world not mathsworld.
 
Flat universe theory- sounds like some bullshit.
http://curious.astro.cornell.edu/question.php?number=171
perhaps its just the website, but they say that the universe is actually flat because .. i'm not even going to try to repeat the mumbo jumbo on the website. Basically, the balloon theory taken literally saying there is nothing towards the center of the balloon...

So, we are to believe that the universe is like the very surface of a balloon? A thin layer expanding out from a center? This would still mean its a sphere. Sphere. SPHHEEEEEERE

Well.
Me, the Cornell professor, understands exactly what is happening here. I cannot hope to convey the information accurately, and anyhow, there is no need. Everyone knows that knowledge is gleaned from the Academy. Instead I will write something trite.

I will not even try to explain to this emailer the truth, because it would take too much time [and comprehension], and my time is valuable. Unlike theirs. I am cornell master. Silly be you. I will have action figures based on me. Pissant.
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Literal words from the author of the website.
 
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kaneda said:
1. Lots of problems with the big bang idea. Do look at something other than the wikipedia.
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You and I can discuss things which aren't on Wikipedia when you finally stop claiming things about the BBT which aren't true and which you could see if you bothered to read Wikipedia.

kaneda said:
2. Nonsense is still nonsense, no matter how many times you repeat it. Odd shapes would lead to some very strange areas of space, which we have never detected.
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Something I've already explained to you. If the odd shape is so vast it's many times larger than the visible universe we'd have no way to tell the difference between it and a flat universe.

kaneda said:
3. With 3D space with everything magically moving away from everything else, a point of origin could be traced back to. Real world not mathsworld.
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Which is entirely consistent with any closed, boundaryless compact space. All of them shrink down to points. Nothing to do with 'mathworld', it's to do with the fact numerous configurations can lead to the same phenomenology so you can't say "Only that one is right!", as you keep trying to do.

kaneda said:
And if pigs flew. How would a torus shaped universe form? Around god's finger?
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Well given we don't understand the quantum mechanical behaviour of gravity in the first pico-pico-second of the universe topological changes could well be possible. You keep telling me to read more and open my mind yet you dismiss everything which you don't already accept or know. I'm trying to tell you there's plenty more interesting possibilities for how the universe develops and you're having a go at me for being close minded?!

/edit

Oh, you've been banned. I bet he blames me for that, like he did on PhysOrg.....
 
That's my fault. The ban is only temporary, so he'll be back. That's not my fault.
 
DRZion said:
Flat universe theory- sounds like some bullshit.
http://curious.astro.cornell.edu/question.php?number=171
perhaps its just the website, but they say that the universe is actually flat because .. i'm not even going to try to repeat the mumbo jumbo on the website.
Click to expand...
Just because you do not understand or like something does not mean it isn't true. The idea of inflation was not developed as a flight of fancy. It was developed to explain several known conflicts between the big bang theory and scientific observations. One of those conflicts was that the universe is very close to flat.
 
D H said:
Just because you do not understand or like something does not mean it isn't true. The idea of inflation was not developed as a flight of fancy. It was developed to explain several known conflicts between the big bang theory and scientific observations. One of those conflicts was that the universe is very close to flat.
Click to expand...

I did more reading and I understand what is meant by 'flat' universe now. It is not the simple geometry but more to do with curvature of space-time or whatnot.

The universe is not flat; we see stars on either side the earth and galaxies can be found by magnifying any arc-second of the sky.
 
Shouldn't this be moved to Pseudoscience? I'd like to over speculate about the shape of the universe :).
 
D H said:
Just because you do not understand or like something does not mean it isn't true. The idea of inflation was not developed as a flight of fancy. It was developed to explain several known conflicts between the big bang theory and scientific observations. One of those conflicts was that the universe is very close to flat.
Click to expand...

From what I understand the space time of the universe is not perfectly flat but slightly hyperbolic, meaning that the universe will expand forever. The physical geometry is not flat. Check this out-
http://www.atlasoftheuniverse.com/12lys.html
If you continue zooming further and further out you will see that the visible universe has a spherical shape.

I'm not sure whether this website is that accurate, because supposedly the observable universe is larger than 14 billion light years
http://en.wikipedia.org/wiki/Observable_universe
"The age of the universe is about 13.7 billion years, but due to the expansion of space we are now observing objects that are now considerably farther away than a static 13.7 billion light-years distance. The edge of the observable universe is now located about 46.5 billion light-years away."
It could be that we observe the stars to be 13.7 billion light years away but then we calculate the extra distance due to red-shift.
 
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