The Grand Contraption
The Persians had sacked Athens in 480; now the ruins were being cleared, there was a theater, and each year in the Dionysiac festival the tragedies of Aeschylus, Sophocles, Euripides, and other authors now known only as names were presented before huge audiences. Originally, they were performed only by a chorus that sang and danced as it told the old tales of pride, doom, and the envy of the gods. Later, one actor was introduced; then Aeschylus used two, and in 468 Sophocles introduced a third. Now it became possible for the audience not only to hear about events but to see them happening.
In the following year or thereabouts, news reached Athens that a large meteorite had fallen near Aegospotami in the region of the Dardanelles, No contemporary records describe this event but later writers refer to it and Pliny, five hundred years later, says the stone was still on view. Almost anywhere in the regions around the Mediterranean, everyone would have regarded the meteorite as bad new, a sign of anger in the sky. But a well-known professor in Athens seems to have seen it in a different way. Anaxagoras (c. 500-c.430) had come to Athens from Clazomenae, an island a few hundred yards off the Ionian coast. If the stories told about him are true, he reasoned that if a big piece of stone fell from the sky it had probably been up there for a while before it came down, and that there might be others. He had already startled Athenians by pointing out that we can explain the phases of the Moon by assuming that although it looks flat, it is actually a sphere with no light of its own, lit by the Sun. Further, to explain its changes of shape we need not think anything is happening to the Moon itself but only that each night, as we look at it from the Earth, it is being lit from a slightly different direction. He taught that eclipses of the Sun occur when the Moon casts its shadow on the Earth. He also taught that the Moon is eclipsed when something, perhaps the Earth, gets in the way of the Sun's light, but since everyone thought the Earth is flat, his discussion can't have been very convincing.
I suspect that few people at the time had thought of the Moon as a thing at all, much less a sphere. The heavenly bodies were regarded as phenomena, things that are seen, visible signs of divine beings. Those who thought of Sun and Moon in a spirit of religious awe considered it blasphemous to ask what these bodies are made of, or to say, as Anaxagoras did, 'The Moon is made of Earth and has plains and ravines in it.' And if the Moon is really like that, what is it doing up there? If a rock fell at Aegospotami, why doesn't the Moon come down? If the Moon is a sphere, why does it look flat? The Sun looks flat and everybody knew the Earth is flat. Besides, if the Moon were a sphere, why would it always show us the same face? Anaxagoras had only one argument in his favor: he could explain its phases.
Having cast off the lines that moored him to philosophy and religion, Anaxagoras headed into deeper water. He proposed that the Sun itself is nothing but a ball of rock, glowing hot and as big as the Peloponnese. This was altogether too much for respectable people. As long as one does not think about their physical nature, it is natural to worship Sun and Moon as gods and to tremble when one of them is eclipsed—but who prays to a piece of rock? Anaxagoras was thus prosecuted for impiety, the crime for which Socrates was later executed, and was saved only by the intervention of Pericles, his friend and former student. He went back to Ionia, where he died in Lampsacus. They say that the people there, awed by his brilliance and his reputation, gave him a public funeral. on his tomb was written:
Here lies Anaxagoras, who above all others
Passed through the limit of the world's truth.