From galaxies to Saturn's rings to our solar system, many celestial objects are flat-out flat. But do you ever wonder why that is -- especially when we live in an ever-expanding, three-dimensional universe?
Henry Reich, creator of the YouTube series MinutePhysics, unravels the mystery of why the solar system is flat in a new video -- just check it out above.
As Reich explains in the video, the solar system formed out of a nebulous cloud of swirling gas and dust that clumped together due to the force of gravity. Particles in the cloud bumped into each other as they spun around a single center of mass, and these collisions eventually led to the cloud's flattening out.
"The whole mass must continue spinning inexorably because in our universe, the total amount of spinning in any isolated system always stays the same," Reich says in the video. "So over time, through collisions and crashes, the cloud loses its loft and flattens into a spinning roughly two-dimensional disc shape like a solar system or galaxy."