system
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human
how are planetary rings stable ?

Something just occurred to me, if all extraplanetary masses formed from from gravitational forces acting on small bits of debris pulling them together, and planetary rings are just that except in a stable orbit around a larger mass, how hasn't the same process happened there ?
gpt
Close enough to a planet, tidal forces will tear apart any moon that's held together solely by gravity. The near side of the moon is closer to the planet so pulled more strongly compared to the far side, and this difference in gravity is stronger than the moon's own gravity.

This also means no object can come together under gravity. Things with different orbital radii will be travelling at different speeds and the gravity between them isn't enough to overcome that.

It is within this distance, known as the Roche Limit, that planetary rings exist. Small moons, held together by the strength of rock and ice, can exist within the roche limit but large ones cannot. A loose object on the surface of such a small moon would float away, in its own orbit round the parent planet that's slightly different to the orbit of the moon.