Galileo first disproved Aristotle's hypothesis that heavier objects fall faster by dropping objects of different weights from the Leaning Tower of Pisa and finding they fell at the same speed. Isaac Newton later established the Law of Gravity and used it to explain the moon's orbit of Earth. Gravity is the force that causes objects to fall and is represented by the mathematical formula F=Gm1m2/d2, where the attractive force between objects depends on their masses and the distance between them.