quantum.

"...how can there be nothing? doesn't that contradicts physics?"

Well, it does seem absurd, your dead right; but the Big Bang theory says that it was the beginning of the space-time continuum and all the stuff that physics deals with. Notice the term "space_TIME". It was the "biginning", with no before. Time itself started. It beats me, too. Don't ask me how it can be, but there it is.

Of, course, the Big Bang theory may prove to be incorrect in it's details, but there's very convincing evidence of which I'm sure your aware.

"Time is what prevents everything from happening at once" - John Wheeler