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Gravity's role is to keep the planets in orbit and balance.
Gravity acts like a magnet â pulling objects together. What causes gravity is not really known. The Earth has gravity. Gravity holds everything close to this planet. Trees, water, animals, buildings, and the air we breathe are all held here by gravity. All of the planets, their moons, and the stars in the universe have gravity. Even our own bodies have gravity. The Earth's gravity is far stronger than our own so we don't notice the gravity our bodies possess. Gravity is affected by the size and proximity of objects. The Earth and the moon have a stronger pull on each other than the Earth and, say . . . , Jupiter because the Earth and moon are closer to one another.