Universe -- open or closed?

[GigaCluster]

I recently had an argument (well, a heated discussion) with someone about our universe:
Is it open, and therefore extends infinitely?
or
Is it closed, and ends somewhere?

It may be just me, but the "open" theory is just too much to fit comfortably in my head. I cannot comprehend how something can extend infinitely, probably because nothing on Earth matches this.

If it's closed, what is that boundary? And what (if anything) is beyond that boundary?

I know that nobody knows this for sure, but what is your opinion regarding this issue? Don't just post "Closed." or "Open." -- try to explain why you feel that way.

 

[Martin]

the universe does not extend infinitely, but space probably does.

The universe is simply the collection of all stars and galaxies, its safe to assume that it does end. However, the space where the universise it contained.....probably not.

 

[Haircut]

IMO the universe is infinite in three dimensions, but finite in higher dimensions.

A good analogy is a sphere which is finite in three dimensions, but a two dimensional being on the surface would perceive it as being infinite as which ever way they went they would never reach the edge. Bump up the number of dimensions and you have our universe.

 

[MaxDSP]

Ive read some articles on this and for the most part, they gave me a headache. Things like this the normal mind shall ponder no more.

 

[Fjive]

the universe...to me...i think it's open....i can never imagine that there's an end to it...i like star wars and star trek....makes me fantasize some times...about time and space stuffs....heh

 

[AgentZap]

I've thought about that since I've been like 10. I still have no conclusion. Its incomprehensible. If its closed you are right what contains it? And what contains that container????? If it is infinetly big then like that just blows away the mind. Where does all that space exist? Really just doesn't make any sense.

 

[chuckieland]

the chicken appear first or the egg appear first

 

[Rison]

Haircut may be right. The physical universe may be the center of the whole universe.

 

[Elledan]

There's no final conclusion yet. So far the Universe is expanding, but whether this continues depends on whether there's enough mass in the universe to stop this expansion. With the currently known amount of particles, there's no even nearly enough mass to arrest this expansion, but if it's true that the universe contains a large amount of so-called black matter (i.e. matter which is not observable because it doesn't reflect light), and much more than there's 'normal' matter, then the expansion of the universe will be arrested by gravity and space will 'fall back', so that the universe will end with a 'big crunch'.

Otherwise, the universe will expand until all matter and energy has been pulled into black holes and it becomes an empty place, without any form of energy. Ultimately, those black holes will be pulled together and form one giant black hole, which might - according to a theory - transform into a white hole, which would then cause the 'birth' of a new universe. A so called 'big bang'.

 

[Rison]

Like everything, time has its beginning (and its eventual end). Since space is intertwined with time, there may be a limit to it as well. We we discuss time, we must view things from a scientific point, not a literal (or artistic). We cannot be like God and view things from the outside. We can't see a "beginning" or an "end," cause that'll be the end of us as well. If one was to take that view, then time is infinite. Personally, when we attempt to comprehend things on grand scale, we must also look at things on a minute scale. In the end, there may be no difference at all. Small and great are probably one and the same. With that said, I believe that the universe is closed and infinitely open at the same time, like the sphere. In terms of physical, it may all be an illusion. Things may appear to be large, but, like the sphere, we may be going (and looking) in circles. When we're looking ahead, we're actually looking back (in time and, hence, space). It's an illusion.

 

[fatalbert]

The dimensional idea may be a good one. However, there is no way for humans to actually observe and measure higher dimensional reactions or occurences. therefore, we will never actually know.

 

[Cattlegod]

<< Haircut may be right. The physical universe may be the center of the whole universe. >>




hehe, reminds me of when they used to say the earth was the center of the universe

the plain fact iswe don't know, and we don't have the ability to know at our current understanding, we can only guess. we may well find out that the universe is just as small to the rest of the picture as our planet is to the universe.

and i believe the universe is defined as the collection of all galaxys, so the universe would extend only to the edge of the furthest galaxy. however, space extends further.... but no one knows how far.

 

[Haircut]

All points in the universe are at the centre because everything is moving away from everything else (on a large enough scale)

I don't think there is any real doubt as to whether the universe has bounds. The only way the universe could be truly infinite is if it has existed for ever. Since the big-bang theory is almost certain to be correct then there is no possible way for the universe to be infinite as it started expanding a finite amount of time ago.

I don't think space or time exist outside the universe as these are properties of the universe and cannot exist independently from it.

 

[HombrePequeno]

I think the universe is finite but it doesn't really have a boundary. You could basically go in any direction 'straight' and eventually end up back where you started.

Scientists think that the universe is speeding up. They blame the speeding up on dark energy. What is dark energy? Energy they haven't found yet of course.

 

[Ultima]

<< IMO the universe is infinite in three dimensions, but finite in higher dimensions.

A good analogy is a sphere which is finite in three dimensions, but a two dimensional being on the surface would perceive it as being infinite as which ever way they went they would never reach the edge. Bump up the number of dimensions and you have our universe. >>



Yes, but what you're describing is not an "infinity" either. Would you claim that the Earth's surface is infinite? Didin't think so. Just because something wraps around doesn't make it infinite.

 

[Haircut]

OK, infinite was a bad word - what I meant was that it has no end in the number of dimensions in which we think.
If we could travel far enough in our universe I think that we will eventually get back to the same point.

 

[dman]

I prefer to think of it as infinite.

There's those finite theory folks that think that it bends and twirls like the infinity symbol and so when you travel in any direction you will eventually get back to the start... but, I don't buy that. If I just travel out in any one direction, and end up back where I Started, then that means that I didn't keep my intended course in the one direction.

Anyway, while I'm alive I'll never know the answer so I prefer to remain blissfully ignorant. Back to the Pr0n.

 

[HombrePequeno]

<< I don't buy that. If I just travel out in any one direction, and end up back where I Started, then that means that I didn't keep my intended course in the one direction. >>



Think of it like going straight on Earth. Eventually you do end up back where you started.

 

[j0lly]

Where is Elledan when you need him.

 

[dman]

<< Think of it like going straight on Earth. Eventually you do end up back where you started. >>


That's exactly my point though, you aren't going straight, you are going in a curve (straight would be relative to the earth's surface. ) If you went straight in space, you'd have to go forever cuz if you hitsomething to stop you, what's on the other side?

I certainly don't know the answer, but, that's my thinking.

 

[HombrePequeno]

Well you can't really go straight in space then because it's curved.

 

[Haircut]

You don't go straight in space either, space-time is curved it's just that we don't notice it as we are curved in the same way as space-time is.

 

[ImTyping]

The latest, best scientific theory says that it is open. Here is a primer on cosmology today.

 

[Ultima]

<< I prefer to think of it as infinite.

There's those finite theory folks that think that it bends and twirls like the infinity symbol and so when you travel in any direction you will eventually get back to the start... but, I don't buy that. If I just travel out in any one direction, and end up back where I Started, then that means that I didn't keep my intended course in the one direction.

Anyway, while I'm alive I'll never know the answer so I prefer to remain blissfully ignorant. Back to the Pr0n. >>



Well, you can walk around the earth in a perfectly straight line and end up back where you started...

 

[Ultima]

<<

<< Think of it like going straight on Earth. Eventually you do end up back where you started. >>


That's exactly my point though, you aren't going straight, you are going in a curve (straight would be relative to the earth's surface. ) If you went straight in space, you'd have to go forever cuz if you hitsomething to stop you, what's on the other side?

I certainly don't know the answer, but, that's my thinking. >>



maybe you wouldn't hit anything. Maybe you'd just overflow the co-ordinate system and crash the universe