I think anybody that wants to understand the Big Bang should read cavediver's posts on the subject. One such post can be found
here, which I will quote for your pleasure:
cavediver writes:
Now, if we put in an infinte uniform mass distribution (like dust scattered through empty space) we get a different solution. The idea is that this distribution mimics the universe on the largest scale. This solution describes space-time as a finite hyper-sphere that starts with zero size (and hence infinite density), expands to maximum, and then contracts back to zero size.
Shortly after General Relativity made this prediction, Hubble came along and formulated the Redshift Distance Law of galaxies which is consistent with the predictions of General Relativity. That is, General Relativity predicted the nature of the universes expansion (and its hotter and denser past), and Hubble discovered that the expansion part of it was right.
Later, the cosmic background radiation was measured, this time confirming the prediction that the universe was much hotter and denser in the past, viz. The Big Bang.
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