"The Big Crunch"

[WackyRacer]

Does anybody like this theory?
If you aren't familiar with this theory, the basic point is that the universe will end in a big crunch. The big crunch would be like the big bang reversed, so instead of expanding from one point it would now retract to one point.

http://archive.ncsa.uiuc.edu/Cyberia/Cosmos/CosmosFate.html

<--- Basics

Personally i like the idea of the big crunch being the beginning of a new big bang. This is more appealing to me than everything coming to a halt. I like to think of it as a cycle filled with cycles. Inside the continual expansion and retraction of the universe (We may not be the first universe) we have the cycle of how galaxies and stars are formed, how planets are formed. On our planet we have the cycle of life, the food chain etc. There are many cycles within cycles and i like this idea over the idea of this being everything.

I am not trying to say that our life on earth is everything, i would definitely not say that. I suppose this just leaves me with the idea that anything is possible. In the next big bang the human race may not exist, maybe there will be a different version of our race. Perhaps there won't be any life forms?

Anyone care to share their thoughts?

[ypb9fzl3]

As far as I've heard, the "omega constant" is probably a little greater than 1, so the big crunch will never occur.
All planets will separate from each other and the gravitation will not be able to hold everything together. Eventually the universe will cool down.
But we don't have to worry. Our sun will become a red gigant and consume the earth before that..

[WackyRacer]

According to the link i provided if omega > 1 then the big crunch will happen unless you have a better source?
Also i would like to know where you heard that omega > 1?
Just out of curiosity.

[ypb9fzl3]

First, I want to quote wikipedia:
"However, if the universe has a large amount of dark energy (as suggested by recent findings), then the expansion of the universe can continue forever – even if omega > 1"
Wikipedia is not scientific, but I couldn't find a better source at the moment.

My source for omega > 1 is figure 8 in http://panisse.lbl.gov/ (http://www-supernova.lbl.gov/public/pap ... BClust.pdf)
Note that omega = omega_lambda + omega_M.
Omega_lambda is the vacuum density and omega_M is the matter density (both dark and normal).
The vacuum density contains the dark energy. That explains why we can have omega > 1 and an expanding universe at the same time.

Your source is only correct if there is no dark energy (omega_lambda=0).

[TheMindRapist]

Hmm, I was reading about this actually.
Ending in a big crunch would be kinda cool, but there is still plenty of room for the universe to expand.
Not gonna be around to see it.

[Kuja]

I'm going to reply to this, cause it's pretty insulting. The big crunch is never going to happen, all chance of that was lost over 5 billion years ago. If it was to happen the universes expansion would have to be decelerating, however it's accelerating. Accelerating means it's not slowing down under gravity, meaning it won't get pulled together. I believe 'the big crunch' has been modified to 'the big rip' now.

[TheMindRapist]

Sounds reasonable, my knowledge of string theory is rather out of date.
I need to get some more current books.

[Crystal_Bearer]

I'm going to reply to this, cause it's pretty insulting. The big crunch is never going to happen, all chance of that was lost over 5 billion years ago. If it was to happen the universes expansion would have to be decelerating, however it's accelerating. Accelerating means it's not slowing down under gravity, meaning it won't get pulled together. I believe 'the big crunch' has been modified to 'the big rip' now.

You bring up an interesting point. For those unfamiliar: look up 'redshift'. Most people fail to explain, however, what force could be acting on the celestial bodies to be accelerating them. One theory (ok, mine, as I call: the "Derivative Theory":D) is that the universe as a whole is actually curved such that it creates the "shell" of a sphere. As the celestial bodies cross the apex, they are sped up by the force of gravity of the opposing bodies. This explains why some have redshift in relation to the Earth, and some do not. I, personally, do not believe that the Earth as crossed such an apex, but it's theory as-is anyway.

[Ntvu]

Didn't some people also believe that in 2000 the world would end?
So they killed themselves, then the year 2000 came.. and nothing happened. So I don't really believe all of the Big Crunch theory, and there's not enough evidence to prove this.

[Teh_noob]

If the universe has a defined boundary, then where is it? Most of the universe is just space where there is no matter or anti-matter. So the edge of the universe must be the infinite number of points where space meets matter, otherwise it would continue on forever which would mean that there is in fact no universe, only clumps of matter/anti-matter. If there is a "wall of matter" on the outside of the universe, why is it not on the inside, and the universe continues on past it?

That's my theory which contradicts the alternate theory of the big bang and a limited universe.