Posted: Oct 06, 2011 2:42 pm
by newolder
Dudely wrote:
newolder wrote:
Dudely wrote:

Are you being facetious? Perhaps preying on an imperfect analogy?

The universe is expanding because for some crazy unknown reason it started expanding at the big bang. Gravity is slowing it down by. . . being gravity. At a certain density the matter in the universe should be enough to let gravity take over and collapse everything back again.

isn't this primitive cyclic model what the prize winning entry disproves by repeated experiment? :ask:


I said "At a certain density the matter in the universe should be enough to let gravity take over and collapse everything back again." I did not say the density IS above that value, or that it ever would be. In fact- as I explain a few sentences later- it isn't.

Then i shudve read further. :oops: Sry.
Precisely because we don't see the expansion slowing down we know this not to be the case. However, we have to add a bunch of crazy unproven variables into the mix to make all our observations jive with one another. This is what dark energy and dark matter is for.

I don't know what u mean by crazy and/or unproven but dark matter accounts for (amongst other things) the rotation speeds of stars in galaxies (neither crazy nor unproven) and Einstein's (not even a mistake) cosmological constant accounts 4 accelerated expansion. :scratch:

If the density was above that critical value a collapse is what would happen. You can do the math yourself if you like- I did, so it cant be that hard :lol:. Of course, now we have to take into account all the dark stuff, but we really don't even know if that's the right answer yet.

Wheeler and/or de Witt published all teh necessary calculations, iirc.
:cheers: