infinite universe and big bang singularity

DrStupid

I am still talking about infinite distances. Distances between given points are something completely different. The latter are finite and shrink to zero in the big bang singularity. The former do not need to be zero in the singularity which therefore do not need to be a point.

Naty1

kuartus:
no, he did not say the GR is predomininant....In fact on page 713 he points out that for a black hole singularity
and no the the second part as well:

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

This again shows an emphasis in favor of quantum theory over relativity.

jcsd

There no such thing as 'infinite distances', at least not in this scenario.

What you are trying to say is that whilst all distances tend to zero, the length of say an infinitely-long curve in space will not tend to zero will remain infinite as t->0.

This is somewhat moot as the singularity is not a point on the manifold.

phinds

No, that would imply that the singularity was a point. I'm not aware of any reputable physicists who think that the singularity was a point in SPACE, as you imply, it was a point in TIME and no one KNOWS what it was in space, except that it wasn't a point because that would make no sense.

jcsd

If you read what I said earlier, he is correct all proper distances tend to zero at the singualritiy. The big bang singualrity is a bit like a "place" and a bit like a "time", as by artifically inserting an event to represent the big bang singularity you can make a "manifold with boundary" (at least for idealized solutions).

However the big bang singualrity is not naturally an event in spacetime and there's no general way of adding boundaries to manifolds to represent singularities.

Naty1

I just happened to see Roger Penrose description of the big bang singularity in THE ROAD TO REALITY pg 722.........He uses the balloon [surface] two dimensional analogy....

jcsd

I think that's spefically to do with the Euclidian path intergral approach to quantum gravity.

phinds

I agree w/ "tend to zero", which I take to mean "approach zero without reaching it". He said "go to zero" which I take to mean REACH zero, which I disagree with. Do you belive that the singularity was a dimensionless point in space? If it was not, then the distance only tends to zero, it does not GO to zero, and my statement stands.

jcsd

I think we often say "goes to" as a synonym for "tends to", I certainly used it in that sense earlier in the thread.

The singularity as a dimensionless point that constitutes the whole of space is certainly one way of looking at, with the reservations I expressed above though.

DrStupid

I am not sure about the correct English wording. How about "The limit of r as t approaches zero is zero for a finite r. But it do not need to be zero if r is infinite."? In German I say "r geht gegen Null". I literally translated it as "r goes to zero". Maybe this was wrong.

Just to make clear, what I mean with infinite distances:
Separate the distance r between two objects into finite segments of equal length an number them beginning with 1. Now assign segment 1 to segment 2, segment 2 to segment 4 and so on. If you can assign each segment i to another segment 2·i than r is infinite.