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Archimedes [ar' ki mE' dEz] scientist and inventor Archimedes was born in Syracuse, a Greek colony on the island of Sicily, about 287 B.C. He lived and worked there all his life except for a few years of study in Alexandria. His Discoveries Pi. Archimedes' only surviving published works are his mathematical treatises. In Measurement of the Circle he worked out the ratio of the length of a circle's circumference to its radius to a degree of accuracy never before achieved. He did this by a technique which would not be replicated again until the discovery of differential calculus by Isaac Newton nearly 2,000 years later. Buoyancy. Archimedes made his bestknown discovery as the result of his friendship with Hieron II, ruler of Syracuse, who often turned to the mathematician for advice and guidance. On one such occasion Hieron had bought a gold crown from a local goldsmith. Hieron doubted the goldsmith's honesty and wanted to be sure the crown was actually made from pure gold, so he asked Archimedes to check the gold content without damaging the crown in any way. Although he spent several days on the problem, Archimedes couldn't come up with an answer. Then, while stepping into a full bathtub one day, he suddenly noticed a wash of water overflowing the sides. Upon further thinking he realized that the amount of water displaced from the bath was equal to the volume of his own body entering it. He had finally found the answer to Hieron's problem. If he immersed Hieron's crown in water and measured the volume displaced, he would know the volume of the crown. To determine whether it contained any metal other than gold, he had simply to compare the total weight of the crown with the weight of that given amount of gold. According to legend, Archimedes was so excited by his discovery that he ran naked from his bathroom into the streets of Syracuse crying "Eureka!" (meaning I have discovered it!). Archimedes did indeed perform a buoyancy test on Hieron's crown, and found that it contained a far higher percentage of base metal than the goldsmith had promised, and Hieron promptly had the goldsmith executed. Archimedes later extended his buoyancy principle to show that a body in water received an upward force, called an upthrust, equivalent to the weight of water it displaced. This explains why heavy objects can float. For example, a modern ship built of steel can float because it displaces a large volume of water, while a single bar of the same metal will sink in an instant. Lever. Archimedes' fascination with mechanisms led him to explore the principle of the lever. He showed how a lever, pivoted about a fulcrum, could lift a heavy weight with a relatively gentle force applied to the end of the lever's arm. He reportedly told a friend: "Give me a place to stand and a lever long enough and I will lift the world!" His Inventions The Archimedean Screw is a device still used to lift water for irrigation. As the handle is turned the water is carried upward within the spiral chambers as the screw revolves. The water comes out of the upper end of the screw. Siege Defenses. Archimedes spent his final years helping defend Syracuse from invading Roman armies, which had been besieging the town for three years. Time and again their attacks were beaten back by strange machines designed by Archimedes. One of these machines was a catapault, a weapon that shot rocks at the enemy. Writers of his day claimed that Archimedes invented grappling hooks that could seize ships and disable them. They also said he designed a system of mirrors that concentrated the sun's rays to set enemy ships on fire. His Death Despite Archimedes' machines, Syracuse finally fell in 212 B.C. and the city was sacked. The Roman commander Marcellus gave orders that Archimedes was to be brought to him and treated with honor and kindness. According to a contemporary story, one of the Roman soldiers came across Archimedes as he was deep in thought. When the soldier tried to get Archimedes to come with him to see Marcellus, Archimedes impatiently waved the soldier away saying "Go, do not disturb me!" Furious at the implied insult, the soldier reportedly drew his sword and struck Archimedes dead. SEE ALSO 
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