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Anaxagoras of Clazomenae was a Greek mathematician and astronomer. He was born in 499 B.C. and died in 428 B.C. in Lampsacus, Mysia. After Pythagoras, Anaxagoras of Clazomenae dealt with many questions in geometry... Anaxagoras was an Ionian, born in the neighborhood of Smyrna in what today is Turkey. We know few details of his early life, but certainly he lived the first part of his life in Ionia where he learned about the new studies that were taking place there in philosophy and the new found enthusiasm for a scientific study of the world. He came from a rich family but he gave up his wealth. Although Ionia had produced philosophers such as Pythagoras, up to the time of Anaxagoras this new study of knowledge had not spread to Athens. Anaxagoras is famed as the first to introduce philosophy to the Athenians when he moved there in about 480 BC. During Anaxagoras' stay in Athens, Pericles rose to power. Pericles, who was about five years younger than Anaxagoras, was a military and political leader who was successful in both developing democracy and building an empire which made Athens the political and cultural center of Greece. Anaxagoras and Pericles became friends but this friendship had its drawbacks since Pericles' political opponents also set themselves against Anaxagoras. In about 450 B.C. Anaxagoras was imprisoned for claiming that the Sun was not a god and that the Moon reflected the Sun's light.

The citizens of Athens ... passed a law permitting impeachment of those who did not practice religion and taught theories about 'the things on high'. Under this law they persecuted Anaxagoras, who was accused of teaching that the sun was a red-hot stone and the moon was earth.

We should examine this teaching of Anaxagoras about the sun more closely for, although it was used as a reason to put him in prison, it is a most remarkable teaching. It was based on his doctrine of "nous" which is translated as "mind" or "reason". Initially "all things were together" and matter was some homogeneous mixture. The nous set up a vortex in this mixture. The rotation system is present. Anaxagoras also shows an understanding of centrifugal force which again shows the major scientific insights that he possessed.

Anaxagoras proposed that the moon shines by reflected light from the "red-hot stone" which was the sun, the first such recorded claim. Showing great genius he was also then able to take the next step and become the first to explain correctly the reason for eclipses of the sun and moon. His explanation of eclipses of the sun is completely correct but he did spoil his explanation of eclipses of the moon by proposing that in addition to being caused by the shadow of the earth, there were other dark bodies between the earth and the moon which also caused eclipses of the moon. It is a little unclear why he felt it necessary to postulate the existence of these bodies but it does not detract from this major breakthrough in mathematical astronomy. There is also other evidence to suggest that Anaxagoras had applied geometry to the study of astronomy.

Aristotle both found much to praise in Anaxagoras's theory of nous. Both Plato and Aristotle, however, were critical of the fact that the driving force of the nous as proposed by Anaxagoras was not ethical. They wanted nous to always act in the best interests of the world. In fact the nous of Anaxagoras does provide a mechanical explanation of the world after the non-mechanical start when the vortex is produced. It is worth noting that Newton's mechanical universe would have more in common with Anaxagoras's views than the continuing ethical intelligence proposed by Plato and Aristotle.

We can obtain some clues to the mathematics that Anaxagoras studied but, unfortunately, very little remains in the records to allow us to know of definite results which he may have proved. While in prison he tried to solve the problem of squaring the circle, that is constructing with ruler and compasses a square with area equal to that of a given circle. This is the first record of this problem being studied and this problem, and other similar problems, were to play a major role in the development of Greek mathematics.

One other intriguing piece of information comes from the writing of Vitruvius, a Roman architect, engineer, and author who lived in the first century B.C. He records information about the painting of stage scenes for the plays which were performed in Athens and says that Anaxagoras wrote a treatise on how to paint scenes so that some objects appeared to be in the foreground while other appeared in the background. This fascinating comment must mean that Anaxagoras wrote a treatise on perspective, but sadly no such work survives.

Anaxagoras was saved from prison by Pericles but had to leave Athens. He returned to Ionia where he founded a school at Lampsacus. This Greek city on the Asiatic shore of the Hellespont was the place for the worship of Priapus, a god of procreation and fertility. Anaxagoras died there and the anniversary of his death became a holiday for schoolchildren.