What was the Big Bang?

You ask: What big bang?

Everything Caveman see — stars, rocks, Caveman — start long, long back. Thirteen billion winters and more. Back then, all of everything squeezed super hot, super packed. Then space itself begin to stretch, everywhere at once. Big Bang not bang IN space, like rock thrown in cave. Space itself grew, and stuff rode along — like dots painted on hide: stretch hide, every dot move away from every other dot. Universe stretch and cool; gas clump into stars, stars clump into big star tribes called galaxies. How Caveman know? Two clues. Far galaxies still rushing apart now. And whole sky glow faint with leftover warmth from hot young days — warmth now less than three degrees above coldest cold there can be. What come before bang? Science tribe still argue — nobody know yet. Cave wisdom: Big Bang not explosion in space. It space itself starting to grow.