As far as we know, it happened only once.
According to the believes of physics and the big bang, we know that the big bang was both big and a bang. Since we are still receiving radiation from the big bang, So considering that factor I would say that it was big and a bang. What do you believe?
Big Bang - Big Bang album - was created on 2009-08-19.
Current theory is the Big Bang
The Best of Big Bang
How did it what? - It isn't known what caused the Big Bang, if that's what you mean.
The Cosmic Microwave Background is not "unique" in having a spectrum that matches perfectly that of a blackbody radiator, but that is significant. It is quite unique for astronomical radiation by being isotropic to within one part in 100,000. These two facts are easy to explain if the Big Bang happened as we conclude it did, and impossible to explain with any other hypothesis.
The big bang created itself.
big bang: This is the big bang theory
the big bang of couse
The big bang is a theory.
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Everything we know of happened after the Big Bang.