If you ask a scientist where the Universe got its start, “the Big Bang” is the answer you’re most likely to get. Our Universe full of stars, galaxies and a cosmic web of large-scale structure, all separated by the vastness of empty space between them, wasn’t born that way and didn’t exist that way forever. Instead, the Universe came to be this way because it expanded and cooled from a hot, dense, uniform, matter-and-radiation-filled state with no galaxies, stars, or even atoms present at the start. Everything that exists in its current form today didn’t exist 13.8 billion years ago, and all of this was figured out during the past 100 years. But even with all this, there are a whole slew of facts most people — even many scientists — don’t quite get about it. Here are our top 10 facts about the Big Bang!