Is the Universe Flat?

[Josh]

I was having a conversation tonight with a few people about the universe and gravity and a number of other things. Discussing how things exist in different dimensions etc etc. We discussed wormholes and rips in the fabric of space too. Something that was mentioned on here a while ago came to mind. It was to the effect that if you were to travel in one direction trying to hit the "end of the universe" that you'd never return to the same point you started at. Is that true (definitively) and if not why not? It would seem that if wormholes were able to "poke" through space and pop out at other places then the universe cannot be viewed like an explosion with a shock wave spreading outward. If the universe is - as we are taught - expanding only into itself then the universe itself must be curved. right? To simplify, I am wondering whether the universe is like the round earth. if you walk and walk in a straight line you'll eventually end up at the point you began. Thoughts? comments? ... Answers??

Josh

[Haglund]

As far as I know, our universe can be seen as that of the surface of an expanding balloon. Finite, expanding and flat, and you can go in any direction forever without reaching an edge. But instead of living on the two-dimensional surface of a three-dimensional balloon, the universe is the surface of a four-dimensional hypersphere. That's how I understand it, but I could be wrong and in that case, I hope someone could correct me...

[KB3HTS]

Awhile back a team of scientists using a balloon in Antarctica (COBE? not sure) announced that based on background radiation the universe is flat. So basically a triangle in our universe has all its angles equal to 180 degrees all the time. If the universe had another shape it wouldn't be true.
My personal favorite cosmological idea, btw, on the shape of the universe is how it could theoretically be shaped like a Mobius strip. For those who don't know what this is, it's basically the shape of a strip of paper with the ends flipped (not a good explination, I'm sorry!). So basically it only has one side. So if the universe were like a Mobius strip and you went away from Earth you would eventually come back and everything would be the same except your view of right and left would be the opposite of everyone else's!
I'm sure I just made everyone really confused with that last paragraph... sorry... :(

[Josh]

Thanks guys. (welcome to the place Parker!)

I understand the theory of the expanding balloon. That is more, i thought, a comparison between the expansion and the how the universe is unending ... expanding into itself. Out of that is where my question arises. The two dimensional surface of the balloon is supposed to symbolise the expanding universe (of however many dimensions). The skin of the balloon is curved in on itself, hence the notion that the universe is only expanding into itself instead of a something. Furthermore, If the universe can be spattered with wormholes that poke through to other parts of the universe doesn't that also give support to the idea that the universe has to be curved in some manner? That the universe can cause such great gravity at a point to allow it to act at two points in space (or time etc) at the same instant must mean that the universe can't be flat ... at least the "space" part of the universe can't be flat. Perhaps more like a cruppled piece of paper? I don't know. We know that gravity is essentially curved space, so I still wonder if we can travel in one direction and return to the starting place?????

[kashi]

If 4 dimensions are curved around the outside of a "sphere", then travelling in "one direction" would involve time travel as well.

[Haglund]

Actually, I don't know how things would be if wormholes did in fact exist. Would they be impossible in an expansionally flat universe?

[Josh]

I have no idea. I think the idea of humans even trying to conceptualise this sort of stuff is a little bit beyond us. Well ... beyond me anyway ... like envisioning a 4D sphere and all. the human brain just can't do it. Doesn't stop us talking about it though. So now we have two questions on the run...
- Can the universe be curved? Can it be one enclosed loop? (it is a closed system after all)
and ...
- Can wormholes exist if the universe is flat?

[kashi]

Enclose loop indeed, but not a 3 dimensional one that we can visualise. We couldn't travel around it and arrive back at our destination, because we'd be travelling through more than 3 dimensions and that just isn't done!

Our visualisations don't cut the mustard.

[imported_Astrono]

[SIZE=14]
If I walked and walked in a straight line
I would fall off cause the universe is flat!
:lol: :lol:

[Faulkner]

If 4 dimensions are curved around the outside of a "sphere", then travelling in "one direction" would involve time travel as well.

Yes, but if you were travelling faster than light, you would meet yourself departing!?

However...If the universe is indeed flat, as the latest measurements seem to indicate, then for the life of me the universe MUST be expanding into something, and must have a spherical "boundary". To say the universe is expanding into "nothing" is absurd. "Nothing" is just a word for "unknown".

I don't think you can say the universe is "flat" (geometrically), and also say that the universe can be likened to the surface of a balloon (but in 4D). You can't have your cake & eat it too! If the universe is flat, then wouldn't it be more accurate to liken it to a sheet of paper that is getting bigger? I don't think the balloon analogy works, it just confuses everyone. We need another analogy!!!

[Haglund]

I think they mean that the universe is not flat like a sheet of paper (apparently this is not so), but that it is expansionally flat.

[Haglund]

Ok, here is apparently the latest theory on what shape the universe might have.

http://www.space.com/scienceastronomy/univ...cer_031008.html (http://www.space.com/scienceastronomy/universe_soccer_031008.html)

[Josh]

Wow! Parker!! That was an impressive find. I'm a little blurry eyed (given that it's late and trying to fathom other dimensions is a little difficult at the best of times) after reading the difference between finite and infinite universes. It seems like the infinite universe meant an open system? which seems odd given that the universe being infinite means it is the only system ... anyway ... After reading it I don't see the difference between an infinite closed system universe and a finite closed systm universe.

But to answer my original question ...


The new idea involves blocks of space "with opposite faces abstractly glued together," the researchers write in the Oct. 9 issue of the journal Nature. An object sliding off an edge of one block will instantly slide into view at the edge of its opposing block.

That it seems to suggest that you would infact return to the same place you started if you continued along the same trajectory for a good while. That is mindboggling. The universe is truely an amazing place.

I am now going to go and wonder at the idea of a universal round trip.

I recommend we all vote Parker man of the week!

[imported_ROB]

Josh

i found this link that tells how the universe is football like shape

have a look....

Tantalising evidence hints Universe is finite (http://www.newscientist.com/news/news.jsp?id=ns99994250)

[Haglund]

And here is another article in Nature:
http://www.nature.com/nsu/031006/031006-8.html

The fact that the universe would be bent in such a way that it is finite but still have no center, and when you travel in one direction you'll end up where you started, is very difficult to imagine.

[Josh]

I have a lot of reading to do .. including all the links at those urls. It seems like the universe we live in is like a big game of Asteroids with everything flying out of one end of the screen and in the other.

Thanks guys.

[Josh]

Fraser, you think you'd be able to track someone down from these two teams (see the url in ROB's post) and get them to present their respective sides of the theories??? That would be pretty interesting (and similar to what we were talking abou thte other day).

[Matthew]

It is difficult to imagine, but concievable.

[Faulkner]

It's obvious, isn't it? How can an infinite-sized universe originate from a Big Bang singularity? Those articles all mentioned the widespread assumption among physicists that the universe is infinite. I don't understand this?! Surely the real question to be asked is: Is there an edge to the universe? or, Does it somehow twist back upon itself in a seamless closed loop?

This is awesome research!!!

[Josh]

Faulkner, essentially that was the question. Whether the universe was infinite or finite everyone (basically) agreed that the universe had no edge. as far as i know anyway. I'd really like someone with more knowledge in this area to give a better description to what this research means.

FRASER?? :P

[Faulkner]

Yes, fascinating stuff. I can't think of more important research, I think???

But I don't think it's a new idea, like those articles make out. The whole idea of the universe being analogous to the surface of a sphere that we're brainwashed with from Day 1, well, it kinda implies the same exact thing, doesn't it? And I read an old astronomy book from the '50s that stated that an astronaut travelling in a straight line would eventually arrive back at their departure point. So the idea has been around, and I was under the assumption it was what physicists generally believed. Where did the idea of an infinite universe come from? How does a Big Bang give rise to infinite dimensions? That's one helluva inflation!!!

If the whole universe is a closed black hole, then what lies outside it????

Hmmmm.....