To put it delicately, this is just not so. It is only one of several possible interpretations of the Biblical account.
Another way to see Genesis 1:1 is to understand it as a gap in time from "In the beginning..." to "the Earth was (became)..." that can be filled by an undefined period of time.
If you haven’t read it, I’d recommend you look up “The Age of the Universe” by former MIT physicist Dr. Gerald Schroeder (he has a website), in which he does a good job of reconciling Biblical creation and the Big Bang. Fascinating stuff.