180-c. 126 B.C.

Greek Astronomer, Geographer, and Mathematician

Often described as the greatest astronomer of antiquity, Hipparchus (also known as Hipparchos, Hipparchus of Nicaea, or of Rhodes) revealed the precession of the equinoxes, determined the lengths of the four seasons on Earth, studied annual solar movements, and considered the distances of the Sun and Moon from Earth. He was also the first person to use longitude and latitude in an attempt to pinpoint locations on Earth. In addition, he indexed the latitude, longitude, and brightness of approximately 850 stars, creating the most complete astral catalog ever before assembled.

Born around 180 B.C. in Nicaea, Bithynia (in Anatolia), Hipparchus spent much of his life as an astronomer in Rhodes (one of the Greek islands), although he may also have spent some time at Alexandria, Egypt. Although only one of his 14 books remains, a review of Aratus's Phaenomena, his contributions to...