Astronomy
Thales of Miletus [b. Miletus (Turkey), c. 624 bce, d. Miletus, c. 547 bce] correctly predicts a solar eclipse that occurs on May 28, 585 bce; the Medes and Lydians, taking the eclipse to be an ill omen, call off their war. See also 2136 bce Astronomy; 450 bce Astronomy. (See essay.)
MathematicsThales of Miletus proves the first theorems of deductive geometry. Although there is some evidence of reasoning in Egyptian geometry, most geometry before Thales was based on general ideas obtained from measurement. The exact theorems proved by Thales are not known for sure, but he apparently uses logical arguments, although without spelled-out axioms or postulates. See also 1650 bce Mathematics; 430 bce Mathematics.
PhysicsThales of Miletus creates a system explaining matter in which water is the basis of all things. Matter appears to him to exist in three forms: mist, water, and earth. He considers mist and earth as forms of water. In the field of astronomy, which he has learned from the Babylonians, Thales claims that the substance of stars is water. See also 530 bce Physics.
