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Bill S.
2002-Feb-11, 08:14 PM
Hi all...I've got a basic question:

What shape is the universe? Further, if the universe has a shape, then it has a limited volume, and if it has volume it has to exist inside *another* space - that is, if it has an inside and an outside, it's got to be in something. And if it has a shape, a volume, and occupies a space, how theoretically big might it be?

Thanks all.

Another Phobos
2002-Feb-11, 08:28 PM
The universe is either finite or infinite (or perhaps I should say "boundless"). The current indication is that it's infinite, but research goes on.

If it's finite, the concept of shape may still not apply because of the way space would be "curved back on itself". In a finite universe, you can still never travel to an edge...you would simply(!) follow the curvature of space back to your starting point (or another region of the universe anyway).

The universe is pretty much defined as "everything". So, the idea of viewing the shape of the universe from an outside vantage point is somewhat impossible. Either there is no "outside" or anything outside is completely inaccessible to us because we can only work within this time and space (plus "outside" may not even have the same laws of physics so we are even further removed from understanding anything about it).

Perhaps this universe is literally infinite and there's nothing else. Perhaps our boundless universe is a speck in a "larger" infinity or a sea of separate boundless universes (if size comparisons of separate realities has any meaning).

Confusing, eh?

smzarba
2002-Feb-11, 08:38 PM
Please don't say these things. I'm still trying to imagine the smaller structures, like gas clouds 25 ly across.
/phpBB/images/smiles/icon_eek.gif /phpBB/images/smiles/icon_wink.gif

Chip
2002-Feb-11, 08:46 PM
On 2002-02-11 15:14, Bill S. wrote:
Hi all...I've got a basic question...What shape is the universe?


I like this page from the Bad Astronomer (http://www.badastronomy.com/info/links.html) for questions like that!

The BA's No. 3 pick on that page is Ned Wright's FAQ website, which I recommend too. Lot's of interesting far out ideas. /phpBB/images/smiles/icon_wink.gif

<font size=-1>[ This Message was edited by: Chip on 2002-02-11 15:47 ]</font>

Another Phobos
2002-Feb-13, 08:00 PM
The BA's No. 3 pick on that page is Ned Wright's FAQ website, which I recommend too. Lot's of interesting far out ideas. /phpBB/images/smiles/icon_wink.gif


Dr. Wrights site is indeed cool. An equally good (and less technical) site is Dr. Odenwald's...which is the best FAQ site I've seen.

ljbrs
2002-Feb-16, 01:58 PM
It is thought that there is no edge to the Universe (like an expanding balloon, it would be similar to an expanding surface). Of course, we are only able to glimpse a small portion of the Universe, so we would never be able to know for certain about the total extent. If the Universe began (as present understanding indicates) with a Big Bang, followed by an inflationary period, continuing with an acceleration (discovered by the Supernova Cosmology Project and by the High-Z Supernova Search Teamin the mid-to-late 1990's), the visible universe is enormous and getting more so. But, to my knowledge, there is no *edge* in any of the calculations.

ljbrs /phpBB/images/smiles/icon_smile.gif /phpBB/images/smiles/icon_confused.gif

NottyImp
2002-Feb-20, 12:12 PM
The thing is, it's a horrible concept, and for lay-people all but incomprehensible. I sometimes think that even scientists really just "accept" the idea without necessarily being able to fully comprehend it. It's pretty much the same with all advanced astronomical and physical concepts, which is why I wish my maths was better and I could understand all these things in their native language.

SpacedOut
2002-Feb-20, 02:20 PM
I agree with NottyImp – While I find these discussions very interesting I regret I don’t have the math / physics skills necessary to really understand it – same thing goes for Special Relativity – I know the basic rules and accept them only because I’ve memorized some things – not because I have a real understanding of the subject.

If the Universe started in the Big Bang and THEN started to expand – what (area) does it expand into?!?

Makes my hair hurt – not that I can spare any.

(corrected cut/paste error!!! - there goes another hair!)

<font size=-1>[ This Message was edited by: SpacedOut on 2002-02-20 13:49 ]</font>

informant
2002-Feb-20, 03:34 PM
I too feel that I don't have the math/physics skills to fully understand, but here's an attempt:
The way I see it, Big Bang theory doesn't necessarily mean that the universe is "stretching", getting bigger. All that can be said is that some parts of the universe with mass - the galaxies - are getting farther and farther away from each other as time goes by.
Does this necessarily mean that the "edge" of the universe - assuming there is one - is expanding too? I don't know.
The edge of the universe may be in the dark for us, because the amount of time that it takes for light to get here is longer than the age of the universe. So, we can't see it "yet".
On the other hand, if you play the "film" backwards, people usually do say that many billion years ago all matter in the universe was contained in an area about the size of Earth...

>Scratching my head...<

SiriMurthy
2002-Feb-20, 04:00 PM
I sort of vaguely remember reading somewhere (Web/book) that the universe is finite, but boundless. Everything - everything, including space and time as we know it today - was contained (please note the word "contained") in itself at a single point.

As someone has mentioned in this thread, I don't believe that we can view our universe from "outside". If we could, it has to be from beyond our space-time continuum.

Well, if everything was contained in a single poing, what was beyond that point? Was the point containted in something else? I don't know. Yes, my hair hurts too and I don't have many to spare either. /phpBB/images/smiles/icon_wink.gif

DJ
2002-Feb-21, 04:23 PM
Interestingly, the edge of the universe at least according to some theories is neither timelike, nor spacelike. The "edge" is the future of anything currently within it. This is the fundamental principle behind the "no boundary" theory.

In really laymen terms, it sort of becomes defined based on the potential future of any particular point in spacetime. Thus, if a particular point in spacetime needs to go in a certain direction, it will. Could be back into existing spacetime, or out into new spacetime, but that cannot be determined for any specific point.

Thus, the universe may no longer be smooth, as the interaction of points is not predictable. However, that does not indicate that it was not once smooth.

DJ

Wally
2002-Feb-21, 05:07 PM
On 2002-02-20 10:34, informant wrote:
I too feel that I don't have the math/physics skills to fully understand, but here's an attempt:
The way I see it, Big Bang theory doesn't necessarily mean that the universe is "stretching", getting bigger. All that can be said is that some parts of the universe with mass - the galaxies - are getting farther and farther away from each other as time goes by.
Does this necessarily mean that the "edge" of the universe - assuming there is one - is expanding too? I don't know.
The edge of the universe may be in the dark for us, because the amount of time that it takes for light to get here is longer than the age of the universe. So, we can't see it "yet".
On the other hand, if you play the "film" backwards, people usually do say that many billion years ago all matter in the universe was contained in an area about the size of Earth...

>Scratching my head...<


I guess I still have problems with the whole idea of everything starting at a single "point", be it earth size or otherwise. Prior to the BB, there was so "space" as we know it, hence there couldn't be a point of origin as we know it. My brain has a better time of things if I picture the BB as the instanteous formation of our 4D universe (time included) from some other, unimaginable state, Hence there was never really a physical point of origin. Moreso it was more like a "whoosh!!", and there was our universe! (alright, so "whoosh" might be a bit simplistic, but hoping you get the drift. . .)

Catspaw
2002-Feb-21, 06:06 PM
The shape of the Universe is currently debatable, but my best understanding is 'oval', in the simplest terms I can communicate. What is outside the universe, is another unanswerable question that is a good debate for the field of Theology. How big is big? would in essense be that same question. We do know this though, from a recent HST Deep Field Photo, the old object sighted so far is about 10 Billion lightyears away. This distance would put the object in question at a point in time when the universe was about 1/3 it's current age. So we know this, the universe has expanded for 10 billion years beyond that point. That does not mean that the universe is 30 billions LY wide, because with respect to the entire universe, we have not yet devised a means to observe ourselves and place ourselves accuratly within the the structure of the universe...not yet that I know about. As for what lies beyond the universe, we can ONLY speculate, as we have no mean to detect anything outside of everything.

DJ
2002-Feb-21, 09:25 PM
The notion that the universe would be a predictable shape would require that the future be predictable (based on earlier assessment I presented.) It would require that every point continues to expand in the same direction... constantly. It brings up the interesting question of a "timeshape" vs. a "spaceshape." Thus, the future (boundary) appears to be neither spacelike, or timelike.

Something to consider is that up to a certain point, the universe may indeed have been spherical or some other consistent shape. However, interactions of matter beyond a certain timeframe, due to uncertainty, could cause some areas of the universe to have expanded moreso in a given direction than in others others.

The most logical demonstration I could find would be the interaction of galaxies or galactic clusters on one another. Singularities from super- and hyper-nova's could also alter the architecture of spacetime. If you travel in a specific direction forever, it would not be out of context to assume that the universe would expand in the direction you are traveling to accomodate you. Would it expand equally in all places to accomodate your push in a specific direction to maintain it's shape? I can't know at this point.

Hawking covers this conundrum quite well in "The Nature of Space and Time," which in the early chapters tries to establish some basic principles of the shape of spacetime. It took Hawking about 20 pages to describe it, in highly technical terms, so I'm not going to be able to do it here.

Suffice it to say, there's a lot of set theory and mathematics behind what he's demonstrating, and therefore I recommend it as a good read to help with this particular topic.

<font size=-1>[ This Message was edited by: DJ on 2002-02-21 16:42 ]</font>