Gravity is different from the other known forces of nature. All bodies, big and small, accelerate at equal rates in any given gravitational field. That property is opposite to our everyday experience, in which more massive bodies require more work to move or accelerate than less massive ones. That gravity accelerates masses of all size with equal ease is so anti-intuitive that people universally believed otherwise until Galileo?s demonstration at the Leaning Tower of Pisa. He simultaneously dropped a heavy and a light mass (both heavy enough that air resistance was not a factor), and observers below tried to time which hit first and by how much. But to the astonishment of the observers, who were certain that the heavier body would fall faster, the two masses reached the ground at the same time.
