page_title: Archimedes
section_title: Archimedes' principle
hierarchical_section_title: Archimedes / Archimedes the scientist / Archimedes' principle
caption_attribution_description: Block and tackle with six pulleys.
context_page_description: Archimedes of Syracuse was a Greek scientist. He was an inventor, an astronomer, and a mathematician. He was born in the town of Syracuse in Sicily.
  His father was Phidias, an astronomer, and he may have been in the family of a king of Syracuse. Syracuse was a rich Greek city, on the seashore in Sicily. When Archimedes was about ten years old, he left Syracuse to study in Alexandria, Egypt. He was in the school of Euclid, a famous mathematician. Not much is known about the personal life of Archimedes, for example, whether he was married or if he had children.
  When the Romans invaded Syracuse, they captured Archimedes so they could learn all of the things he knew. About two years after he was drawing a mathematical diagram in the sand and enraged a soldier by refusing to go to meet the Roman general until he had finished working on the problem. The Roman killed him. His last words are supposed to have been "Do not disturb my circles!"
context_section_description: Archimedes' principle: the weight of water displaced by an object equals the amount of buoyancy it gets. It has practical uses. It can be used to measure the density of an object, and hence whether or not it is made of gold.
  The story of the golden crown does not appear in the surviving works of Archimedes. Archimedes may have got a solution known in hydrostatics as Archimedes' principle, which he describes in his treatise On Floating Bodies. This principle states that a body immersed in a fluid experiences a buoyant force equal to the weight of the fluid it displaces. Using this principle, it would have been possible to compare the density of the golden crown to that of solid gold by balancing the crown on a scale with a gold reference sample, then immersing the apparatus in water. The difference in density between the two samples would cause the scale to tip accordingly. Galileo considered it "probable that this method is the same that Archimedes followed, since, besides being very accurate, it is based on demonstrations found by Archimedes himself".
caption: A compound pulley, which a person can use to lift heavy loads
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