ASTRONOMER, PHYSICIST

Life
Philosopher and astronomer, Anaximenes is traditionally regarded as the third of the great Milesian philosophers, after Thales and Anaximander. Very little is known about him, beyond the fact that his father was called Eurystratus and that he was a friend and student of Anaximander.


Work
His treatise is said to have been written in a simple and austere Ionian dialect, but even its title has been lost. Aetius tells us that Anaximenes argued that the human soul, which is "air", animates man in the same way that air surrounds and sustains the world. Anaximenes, in other words, held that "air" was the principle of all living things, and that it was constantly and eternally in motion. Air condensed to become cloud, water, earth, or rarefied to become fire, of which the sun was made. While in this theory Anaximenes was close to the thinking of Anaximander, he differed from him with regard to the shape of the earth, for Anaximander, like Thales, conceived of the earth - and all the other celestial bodies - as a gigantic disc. The earth, he thought, was like a cork, floating on the surface of the air. (These theories proved extremely useful in the development of aerodynamics). Anaximenes was the first to realise that the moon took its light from the sun, and thus was able to explain the eclipses of the sun and the moon. He also gave accurate explanations of the formation of clouds, rain, hail and snow.