>>11045246well there are a few answers to this question. at very first, right right after the big bang, it was expanding because of pressure, just like how the pressurized spring makes the clown pop out of the jack-in-the-box when the lid opens. then afterword but still very very early on something called "inflation" kicked in, where basically all of space had more pressure pumped into it because a certain kind of particle (the inflaton) gave off a shitload of energy into space. then after the inflaton was done, it started slowing down. but currently we have something called dark energy speeding it back up, and some people think it is another particle-like thing similar to the inflaton, but it might just be a mysterious "cosmological constant" instead. an analogy for the cosmological constant is like, maybe, how bank accounts have a certain interest rate? like even though you just put your money in the bank, you get more money for free with compounded interest, so it just keeps growing and growing faster and faster on its own because of your positive interest rate just as a rule.
