Space

Why do you think big bang took place?

I imagine that it happened because of reflection of light. Yes you heard it right, reflection of light. We know that silver is the best reflector of light, so it is possible that at that point heat and light was produced by a chemical reaction and light was reflected infinitely leading to very hot and bright. Then one point came and it blasted with infinite heat and light and the universe is expanding with dark matter with the help of this.
This is the best reason I can think about.