There was matter. Without matter big bang cannot happen. What would bang on what? Even for something to bang on each other there needs to be something. A mass, a field, energy, so that field of energy was never created nor destroyed but there was only transformation.
Big bang was only transformation of energy.
From a gas or quantum energy into substantial energy, matter energy, that is all.
This is what the ancient Rishis have said and they called it Anadi (without a beginning) and Ananta (endless).
This creation is beginningless and endless, like the space.
Where is the beginning of space? Where is the beginning of Earth?
There is no beginning, or every point is the beginning and every point is the end.
If you say the globe began here, it has to end at the same point where it began; otherwise it won’t be a sphere.
So these are the brilliant thoughts revealed some thousands of years ago.
Whatever begins wherever should end at the same place and that is a sphere.
So there is no beginning and no end. Anadi and Ananta: The universe is without a beginning and endless.