Actually an answer might be :
What about before a big bang ?
Is the big bang the start ?
A possible explanation might be a continuos expansion and contraction of universe
But as far as I Know, this hypothesis does not fit with the theory
There was one only big bang
Nowadays Science is geared toward atheism
Maybe scientists are wrong , of course but it is a matter of fact
However big bang is more in favour of a religious wiepoint, in my opinion
May anybody suggest a book or article or a web site whereas this topic is discussed ?