Actually, it is not really related to gravity.
The rings of all the gas giants are made of ice, rocks, and dust, but Earth is so close to the Sun, ice can't exist because it will sublime away.
The Earth might once had rings, it is most likely to be formed by a collision with something the size of Mars with Earth. The Earth then had a temporary ring system, then all of them coalesced into what we now call the Moon.
One also has to take in consideration of the Roche limit, which is the closest distance from the center of a planet that a satellite can exist. So stuff below the limit will become a ring, while stuff outside of the limit can coalesce to form larger bodies. Earth's Roche limit is about 9,500 km, which is awfully close to Earth's surface (6,400 km).
Why do outer planets have rings and inner don't?
2 weeks ago
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