Pythagoras (c. 580–500 B.C.) was an ancient Greek philosopher who was interested in numbers and their meanings. He discovered the relationships between mathematics and music, proposing that sounds and their relationships with other sounds can be measured using numbers. He also proposed that the Earth is a sphere, that the Earth, Moon, and stars revolve around the Sun, and that astronomy (the study of stars, planets, and heavenly bodies) could be written as mathematical sentences called equations. Pythagoras and his followers used lines, triangles, and squares made out of pebbles to represent numbers.
Today Pythagoras is best remembered for the Pythagorean theorem: The square of the length of the hypotenuse (the side of a right triangle opposite the right angle) of a right triangle equals the sum of the squares of the lengths of the triangle's other two sides.
Further Information: "Pythagoras and Pythagoreanism." Catholic Encyclopedia. [Online] Available http://www.newadvent.org/cathen/125876.htm, November 8, 2000; "Pythagoras." Internet Encyclopedia of Philosophy. [Online] Available http://www.utm.edu/research/iep/p/pythagor.htm, November 8, 2000; Weate, Jeremy. A Young Person's Guide to Philosophy. New York: Dorling Kindersley, 1998, p. 10.