Projectile Motion: In Aristotle's view, objects moved parallel to the Earth's surface until it was time (i.e. it was their destiny) to fall back to the earth . Aristotle believed that the "natural" state of massive objects was to seek the center of the Earth. When a stone is launched, an impetus is given to it to disturb it from its natural condition. ... Archimedes' catapults lobbed quarter-ton stones at the attacking Roman ships, quickly destroying the clumsy Roman siege engine. ...