Page:Early Greek philosophy by John Burnet, 3rd edition, 1920.djvu/37

Rh observations. The Babylonian names of the planets do not occur earlier than the writings of Plato's old age. We shall find, indeed, that the earliest cosmologists paid no attention to the planets, and it is hard to say what they thought about the fixed stars. That, in itself, shows that they started for themselves, and were quite independent of Babylonian observations, and the recorded observations were only made fully available in Alexandrian times. But, even if the Ionians had known them, their originality would remain. The Babylonians recorded celestial phenomena for astrological purposes, not from any scientific interest. There is no evidence that they attempted to account for what they saw in any but the crudest way. The Greeks, on the other hand, made at least three discoveries of capital importance in the course of two or three generations. In the first place, they discovered that the earth is a sphere and does not rest on anything. In the second place, they discovered the true theory of lunar and solar eclipses; and, in close connexion with that, they came to see, in the third place, that the earth is not the centre of our system, but revolves round the centre like the planets. Not much later, certain Greeks took, at least tentatively, the final step of identifying the centre round which the earth and planets revolve with the sun. These discoveries will be discussed in their proper place; they are only mentioned here to show the gulf between Greek astronomy and everything that had preceded it. On the