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Gravity is the weakest force in the universe, yet it controls the motion of planets, stars, and galaxies. You weigh slightly less at the equator than at the poles, because Earth's rotation pushes you outward a tiny bit. Astronauts in space are not actually without gravity. They are constantly falli…

Gravity is the weakest force in the universe, yet it controls the motion of planets, stars, and galaxies. You weigh slightly less at the equator than at the poles, because Earth's rotation pushes you outward a tiny bit. Astronauts in space are not actually without gravity. They are constantly falling toward Earth, which creates the feeling of weightlessness. A black hole has gravity so strong that not even light can escape it. That’s why it appears completely black. Gravity travels at the speed.