Greek philosopher who wrote critically on Aristotle's dynamic works. Philoponus believed that objects could move in a vacuum, argued against antiperistasis (the theory that an object is kept in motion by air which travels from the front to the back, giving it a push), undermined the distinction between natural and forced motion, and criticized the doctrine of ether. He performed one of the earliest recorded experiments to support his theories, describing the dropping of two differing weights and noting that the difference in falling times did not correspond to the ratio of weights, but was in fact very small. He is important because his refutations were the first logical criticisms of Aristotle.

Additional biographies: Greek and Roman Science and Technology