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them were detailed lists of the rising and setting times for the planet Venus. Drawing up these lists would have required careful observation over a very

long period. Yet the Babylonians were interested in little more than predicting events in the sky so that they could forecast events on Earth. For all its sophistication, Babylonian astronomy had more to do with fortune-telling than science. For the first genuine attempts at a scientific, reasoned explanation for what was happening above their heads, we have to turn to the Ancient Greeks. WHAT IS THE UNIVERSE MADE OF? The Greek philosopher Thales lived in the town of Miletus, in what is now Turkey, around 600 bce . He is generally credited as being the first person we know who tried to answer the question, “What is the Universe made of?” without giving an answer that depended on the supernatural. His solution was, to us, unexpected. The Universe, Thales said, is made of water and the Earth floats in an infinite ocean. He must have been aware of, and influenced by, the beliefs of the Babylonians and Egyptians. Water was vital to the peoples of the ancient world and it should be no surprise that it was given such an important role.

Plato, one of the greatest of the ancient Greek thinkers, believed that the planets moved in perfect circles.

Thales’s pupil Anaximander attempted to draw a map of the whole Earth. It had been long been observed that the stars seen from the northern hemisphere appear to rotate around Polaris, the Pole Star. Anaximander imagined the sky as spheres surrounding the Earth, with the stars on an inner sphere and the Sun and Moon on an outer one. He disagreed with Thales about what the Universe was made of, asking where the water was in things that were hot and dry. Instead, he said that all things arose from a fundamental essence , which was featureless, and unlike anything else. Other thinkers tried to describe the Universe in terms of what was familiar to them. At various times it was said to be made of air, or earth, or fire, as well as of water. Empedocles, who lived in Acragas on the island of Sicily, around

9.