>>11485072>Why does dust and gas form a 2 dimensional disk as opposed to becoming spherical and surrounding the object?Because it's in orbit around the object not a solid shell of material. Every orbit crosses every other orbit in 2 points meaning collisions are inevitable. If you randomly distribute material on various orbits around a gravity well (like a black hole or star or even big rock) eventually all or at least most orbits outside of the dominant orbit flatten out due to collisions. The orbits with least energy and material vanish due to collisions with the objects in orbit with most material and energy and most everything eventually coaleceses into one relatively uniform disk.
Not sure how to intuitively imagine how that happens, I guess you could think of it in 2D with a circular track with marbles or cars going around in 2 different directions, eventually due to collisions the direction with less marbles will stop and every marble will flow in the same direction around the track. Then you just imagine this but in 3D and with many more tracks
