ASTRONOMER

Life
One of the greatest of the theoretical astronomers of the ancient world. Aristarchus was born in Samos in 320 BC, studied with Straton of Lampsacus and lived in Alexandria (288-277 BC), where he made a series of astronomical observations. He was the chief exponent of the heliocentric system, as opposed to the geocentric system of Anaximander, the Pythagoreans, Philolaus, Plato and Archelaus. Archimedes refers to the heliocentric system of Aristarchus in his "Sand-Reckoner", as does Plutarch in "On the complaisance of philosophers". One of the craters on the moon has been named "Aristarchus" in his honour.


Work
Aristarchus taught that the earth revolves about its axis. He added 1/1623rd of a day to the solar year, estimated at 365 1/4 days by Callippus, and calculated the length of the Long Year (luni-solar cycle) at 2434 years.

Up until the 16th century it was generally accepted that the earth was the centre of the universe. It was the Polish astronomer Copernicus (1473-1543) who once again introduced the idea of a heliocentric system, presenting the theory as his own although it was obvious that much of it was drawn directly from the work of Aristarchus. Scientists call Aristarchus "the Copernicus of antiquity"

Principal works:

"Heliocentric system": Lost. Considered by many of his contemporaries as "impious".

"On the Magnitudes and Distances of the Sun and Moon": Extant. Describes how he calculated the sizes of the sun and moon and their distances from the earth

"On Light and Colours"

"Sun dials"

Aristarchus also invented an improved sundial with a concave hemispherical surface and a gnomon in the centre.