The law of universal gravitation, formulated by Sir Isaac Newton in the 17th century, explains why the moon orbits Earth. The law states that every object in the universe attracts every other object with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centers.

In the case of the Earth and the moon, the Earth's greater mass exerts a stronger gravitational pull on the moon than the moon's mass exerts on the Earth. This difference in gravitational forces creates an unbalanced force that causes the moon to accelerate toward the Earth. This acceleration produces a circular motion, which keeps the moon in orbit around the Earth.