Archimedes, (287?-212 B.C.), a Greek mathematician and physicist. He was the greatest mathematician of ancient times and ranks as one of the great scientists of all times. His most brilliant mathematical discoveries included establishing the value of pi (the ratio of the circumference of a circle to its diameter) and devising a system of calculation that was a forerunner of integral calculus.

Because he was intensely interested in the application of theories, Archimedes is considered the father of experimental science. His law of floating bodies, known as Archimedes' Principle, is one of the basic laws of physics. His understanding of mechanical devices such as the lever, pulley, and screw laid the foundation for the science of mechanics. Archimedes also made important discoveries in astronomy and constructed a bronze planetarium in which the earth and heavenly bodies all moved in their orbits when a crank was turned.

Very little is known about Archimedes' life. He was the son of an astronomer and was born in Syracuse, a Greek city in Sicily. After studying at the Alexandrian Museum in Egypt under successors of the mathematician Euclid, he returned to his native city. He devoted his life to study and experimentation and became famous throughout the Mediterranean world. Archimedes wrote detailed reports on his discoveries and conclusions.

When the Romans attacked Syracuse during the Second Punic War, their commander ordered that Archimedes not be harmed. A soldier found the old man tracing geometric figures in the sand, but did not recognize him. When Archimedes refused to move along until he had finished working his problem, the soldier killed him.

Archimedes' Principle states that a body wholly or partially immersed in a fluid is buoyed up by a force equal to the weight of the fluid it displaces, and that a floating body sinks until it has displaced a volume of water equal to its own weight. This principle is of great importance in shipbuilding. It also provides a way of finding the specific gravity of a substance, useful in mining, metallurgy, and chemistry.

According to tradition, Archimedes made the discovery that led to this law while he was at the public baths. He had been asked by King Hiero II of Syracuse to find out whether a new crown was pure gold or whether the goldsmith had used part silver and kept some of the more precious metal for himself. Noticing that water overflowed when he stepped into his bath, Archimedes concluded that a body immersed in water must displace a volume of water equal to the volume of the body. He was so excited over his idea that he rushed into the street crying "Eureka!" (I have found it!)

Gold is denser than silver; in equal weights, gold has less bulk. Archimedes determined that the crown, although its weight matched the amount of gold furnished, was bulkier than pure gold in that amount would be. The goldsmith had indeed kept some of the king's gold and was punished.

In addition to his studies of the circle, Archimedes pioneered in work on spheres and spheroids, cylinders, cones, and other geometric figures. He devised formulas for measuring areas and volumes, and invented a system of expressing very large numbers.

The water-lifting machine called Archimedes' screw was based on an ancient Egyptian device, apparently improved by the Greek scientist. Principles of the lever and the balance discovered by Archimedes were not improved upon until the 16th century. The inventor is supposed to have said, "Give me a place to stand on, and I will move the earth." The story continues that, to demonstrate, Archimedes rigged a mechanism of pulleys and by himself drew a fully laden ship from the water onto the shore.

When Rome attacked Syracuse in 214 B.C. during the Second Punic War, Archimedes turned his knowledge to making war machines. His catapults hurled heavy stones at the Roman ships. Great cranes dropped weights onto them or caught them on huge hooks and upended them. When Roman forces were sent overland, catapulted rocks drove them back. Eventually, however, the Romans starved Syracuse into surrender.