What shape is the universe?

Daniel123 · 2007-05-23 23:18:14

What are everyone's ideas on the shape of the universe?

In my opinion, it is in the a sort of giant donut shape.

I fail to comprehend the fact that the universe is infinite. I do not understand how if you were to keep going, you would continue forever. I then look at the old games where you would fly a rocket - if you went off the left side of the screen you would come back in on the right, and if you went off the top then you would re-enter at the bottom. From fiddling around with shapes in my head, I feel the one that best suits this idea is the donut.

However... you could then pose the question 'what is in the hole in the middle?'... or more significantly 'what is outside it?'.. but that question could be raised with any shape.

Has anyone got any different ideas? or any other factors that could be taken into account?

mathsyperson · 2007-05-23 23:34:59

I get your thinking, but I think it's a bit more complicated than that. Those old games were in 2D, and yet to make the wrapping work the world needed to be shaped like a donut, making use of an unseen third dimension.

So in the same way, if our universe wraps in the z-direction as well as in x and y, then it probably has to somehow be "4D". This is a strange concept, but it's no stranger than the 3rd dimension seems to those little astronauts in that game.

In theory, there may be 4Dians who know exactly what our universe looks like and laugh at our ignorance, but are unaware of what their own 5D universe is.
Taking it the other way, the little astronauts are unaware that they live on a donut, but if they were observing 1Dians who think that they live on a mysterious wrapping line, then the astronauts would know that the 1Dian's world is actually a circle.

This all assumes that the Universe does actually wrap. I think it does, because otherwise it would either be infinite (which it can't be because then it would be infinitely hot) or it would have an edge. But then what's stopping someone moving past the edge and outside?

LQ · 2007-05-23 23:48:34

The start could not be missed, the end could not be found.
To answer your question:
There's there, and there's beyond.

Daniel123 · 2007-05-23 23:52:02

I like your approach, so following on from what you said would these dimensions continue to increase infinitely? The universe is incredibly difficult to understand... it annoys me that i will never know these things.

Identity · 2007-05-23 23:52:31

Our Universe is all there is, there is supposedly nothing outside of it. The Universe IS space and time. Outside of the universe there is nothing, no space, no time.

Daniel123 · 2007-05-23 23:53:49

Identity, how can there be nothing outside of it? How exactly would you recognise nothing?

Identity · 2007-05-24 00:05:17

I dunno, I would think of it as being stuck on the inside surface of a hollow sphere and being unable to walk off because you keep going round again and again.

It would be cool if we could 'tunnel' ourselves out, maybe it's possible, maybe I'm wrong about there being nothing outside, but I think it's what modern science says.

Daniel123 · 2007-05-24 00:06:52

Yess, it would! I always have arguments with my physics teacher about things like this!

Sekky · 2007-05-24 02:13:14

So we're talking hyper-torus, right?

Daniel123 · 2007-05-24 02:20:49

Would you care to elaborate on hyper-torus... i.e. explain to me what the hell it is?!

Sekky · 2007-05-24 02:25:38

Daniel123 wrote:

Would you care to elaborate on hyper-torus... i.e. explain to me what the hell it is?!

A torus is what you described, a big donut, which is three dimensional.

A hyper-torus is a generalisation of a torus to n-dimensional space.

http://en.wikipedia.org/wiki/Torus

There's the page, and I have no idea what dimension this is projected from, but here's a spinning hyper-torus

http://www.lboro.ac.uk/departments/ma/gallery/hyper/mov/hyperTorus.mpeg

LQ · 2007-05-24 02:28:35

So what do we have here... Dot theory? inf. dimensional dot with 0 length yet beginning and end in all possible directions ie. nothing. Decaying to 3d dots called space and mass-dots with more dimensions then that, of compareable length? That sounds like the dotleak, very similar to big bang, not to mention its twin from which it has its origin, a bit religious though. Fact remains: 4root(Inf) = inf, hence the universe can very well have a beginning and do not missunderstand me, it can have an end. but the time between the beginning and end is infinite, -it wont finish, that is. It'll never be done.
A dot is not really a donut ofcourse.

Last edited by LQ (2007-05-24 02:31:44)

Daniel123 · 2007-05-24 02:29:47

oooh i see... !

Ricky · 2007-05-24 02:31:45

You can't make statements about what is outside the universe. Without space or time, we have no concept of what "is" even means. Even saying "outside" implies there is space, which there is not.

Daniel123 · 2007-05-24 02:33:20

LQ · 2007-05-24 02:38:10

Space is like weight, if one is nothing, so is the other. If you say that, all you end up with is a bunch of nothing!

Last edited by LQ (2007-05-24 02:39:29)

Identity · 2007-05-24 02:41:03

Err... hehe... could someone remind me why we are talking about hyper-toruses?

Sekky · 2007-05-24 02:47:46

Identity wrote:

Err... hehe... could someone remind me why we are talking about hyper-toruses?

because there is a non-vanishing continuous vector field on a torus, implying that you can travel in any direction and get back to where you started without destabilising.

but the universe isn't three dimensional, hence hyper-torus is the most obvious place to look next.

Identity · 2007-05-24 03:04:17

But isn't that pretty much the same for a sphere?

Devantè · 2007-05-24 03:18:59

That's easy, the universe is spherical.

I know so since I'm holding it in my hand this very minute. Quite a nice design, don't you think?

luca-deltodesco · 2007-05-24 03:19:38

actually yes, why a torus, and a hyper torus, and not a sphere and hyper sphere?

Sekky · 2007-05-24 03:24:48

Identity wrote:

But isn't that pretty much the same for a sphere?

No, because a sphere does not have a non-vanishing continuous vector field, as demonstrated by the hairy ball theorem:

http://en.wikipedia.org/wiki/Hairy_ball_theorem

Basically, looking at the ball, if you attempt to travel in a straight line from anywhere (taking into consideration lines which you have already fixed in the universe) you end up with points where you aren't moving at all. In the case of a torus, no matter which lines you fix, you can always fix the other lines parallel to it, which is not true for a sphere.

Last edited by Sekky (2024-06-24 08:17:37)

Ricky · 2007-05-24 04:36:44

But why not a coffee cup?

Daniel123 · 2007-05-24 04:38:51

yes... we live in a coffee cup!

Laterally Speaking · 2007-05-24 04:52:20

Here's another theory:

There is a 3-d shape that is the 3-dimensional equivalent of a Mobius strip; the shape, resembling a jar, has only one surface and no edges. Perhaps the universe could resemble this.

Math Is Fun Forum

#1 2007-05-23 23:18:14

What shape is the universe?

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Re: What shape is the universe?

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