When our solar system formed from a swirling cloud of dust, it happened to form in such a way that all planets sit on a single plane. But with all of 3D space to choose from, why did it turn out flat?
Noticing that plenty of other structures in the Universe are flat, too, this Minute Physics video tries to explain why. The answer is based on the way particles in giant dust clouds travel and collide—as well as a quirk of the fact that we inhabit a 3D Universe. But at that point, watch the video, because it explains it way, way better than I ever could. [Minute Physics]