520 bce
Astronomy
Pythagoras of Samos [b. Samos (Greek Aegean island), c. 569 bce, d. Metapontum (Italy) or Croton (Crotone, Italy), c. 480 bce] recognizes that the morning and evening stars are the same heavenly body, the planet Venus. He proposes that the Sun, Moon, planets, and stars move in paths around Earth, which is suspended in space. See also 450 bce Astronomy. (See essay.)
Earth sciencePythagoras recognizes that Earth is a sphere. See also 550 bce Communication.
PhysicsPythagoras discovers that musical harmony can be explained with number (for example, doubling the length of a plucked string produces a note one octave lower). See also 500 bce Construction.






