Gawdzila

This isn't really the case, especially if the universe is infinite in size.
After all, if an infinite universe shrinks in size by any amount, it is still
infinite and therefore has no center.

Like we pointed out, there is no center of expansion on the surface of a
balloon, or in an infinite loaf of bread. It is hard to think of the universe
itself this way. The main point, though, is that the BB had no 'center' so to
speak.

While this is true, that doesn't necessarily mean that the whole universe will
collapse to a point. Only our visible universe will. There are things that are
outside our directly visible sphere. Think if you went to the Andromeda
galaxy, about a couple million light years distant. You would have another,
different visible sphere that overlapped with our current one. Andromeda's
visible universe would also collapse to a point, but it would necessarily be
a different point than ours since Andromeda also sees everything expanding
away from itself.

Think of an infinite sheet of rubber, covered with closely packed, overlapping
spheres each representing different visible universes. One of those spheres
would be ours. Now, if that rubber sheet suddenly expanded, each of those
spheres would move away from each other, but because the sheet is infinite,
there is no center. The spheres would expand along with the sheet, of
course, as the visible universe became larger.

So, the Big Bang is more accurately described as a time when the whole
of space was in a state of incredible density, instead of when the whole
universe was at a single point. This is only accurate when describing our
own visible universe, but there are other visible universes besides the one
centered on earth. For this not to be the case, you'd have to make the
case that the earth was the center of the whole universe (yeah right).

It is time, not a 4th spatial dimension.

Well, space doesn't need room to expand INTO, like a balloon does.
Space is never "made empty" when things expand. Space is simply created
in between points that previously had no space between them. Think again
of points on a balloon when you blow it up. The points move away from
each other, but they never actually move from their place on the balloon's
skin, and thus never 'evacuate' any space. It's just that more balloon is
put in between the points.

BlakeEM

Here's something I found that has just as much proof... and is a lot more interesting... maybe even more proof?

http://uplink.space.com/showflat.php...b=5&o=0&fpart=

Gawdzila

It is.

This isn't quite true. It is only true if you consider the space INSIDE
the balloon, which, for the purposes of the analogy, doesn't exist. Remember,
it is a 2-dimensional example! The center of the balloon only exists in 3-D
space. Space would collapse to a very small sphere (assuming a spherical
balloon of course). Each point on that sphere can still represent a different
center of expansion.
But, as you said, this analogy has it's limits. The actual mathematical
description of a 4-dimensional spacetime manifold is something beyond my
skills at this point. But, suffice to say, we are pretty sure that the earth
is not the center of the universe. We also know that, no matter where you
go in the universe, everything will be expanding away from your position.
Thus, there must be different centers of expansion, and the universe will not
collapse to one single point.

BlakeEM

I say again, before you blow the balloon up the dense matter (empted balloon) must be all together to be dense. To move away or have the space between them expand they must move away from where it just was. This is the central point.

Look at any one point on a balloon and you will see everything move away from it and it stands still, this is the central point. This is for example is the part of the balloon where you are blowing it up. You get a piece of rubber and stretch it and the mark on the center of the rubber isn’t going to move. This again is the center. This would make it seem impossible that the universe doesn’t have a center; that is unless it’s not expanding.

I think the balloon idea makes no sense, you’re using a 2 dimensional object rapped around in a circle to compare to something 3 dimensional. In the universe there would be something inside the balloon because that’s the 3rd demotion and that’s empty because the galaxies moved away from it.

BlakeEM

Go back in time all the galaxies will crash into each other right? Then what before that? Crash into the other crashes and finally into a singularity, a single point of super dense matter. This is a single point and a single point of expansion where everything started getting space between it. If it didn’t come from a single point then what did it come from? Many single points?

This still makes zero sense to me.

Gawdzila

The flaw here is that your piece of rubber is finite in size. If it isn't, then
there is no center and there is an infinite number of centers of expansion.

Yes, I admit that it is a not-entirely-accurate analogy. But, the surface of
the balloon can be considered a 2-dimensional manifold, and that has some
similarities to a 4-D manifold (spacetime).

But in our example, the surface *IS* the universe. That's why the inside of
the balloon doesn't exist. The balloon analogy relies on that point. It is
simply an illustration of how a space can expand without expanding away from
one certain point. The only reason you can identify the center of expansion
of the balloon is because it is a 2-D space "embedded" in a higher-dimensional
3-D space. But, if you were an ant living on the surface of the balloon, you
could not identify the center of the balloon as a point of expansion, you
would simply notice that everything is spreading away from you. Another
ant standing a little ways away would say the same thing. The critical
difference between a 4-D spacetime manifold and a 2-D balloon-space is that
the balloon needs a higher manifold to expand into. Spacetime *doesn't*.
Thus we don't really have a 'center to our balloon'.

Hedshaker

Well, I just watched (some of) the film. Interesting stuff.... right up until the narrator anounced that the whole thing was mention by allah in the quran 14 ceturies earlier proving Allah to be the one true god, or words to that effect.

What's the term? Bait and switch....(?)

I kind of lost interest after that

Orbit

Shadowy Man

But if the rubber sheet is infinite in expanse, where do you put the "center" mark???

Tuvar Ane Ingolenen

Could you not say that in the balloon analogy, the inside is the past, the outside the future? In that case the center of the balloon is the BB singularity.

JPD

Can you define 'now' within that? Is it more complex than your present location? If I was the BB singularity, would everything would be the future, and if I was the outside, would everything be the future or the past?