But this fascination also led Pythagoras to what we now call numerology, a belief in the mystical meaning of numbers. This was an elaborate dead-end. The Pythagoreans also knew that the earth was a sphere and were possibly the first to draw this conclusion, their reasoning based on the outline of the shadow during eclipses of the moon (which they also knew had no light of its own). They thought that the earth always presented the same face to the 'Central Fire' of the universe (not the sun), rather as the moon always presents the same face to the earth. For this reason they imagined that half the earth was uninhabitable. It was the varying brightness of Mercury and Venus which persuaded Heraclitus (who was very close to the later Pythagoreans) that they changed their distance from earth. These orbits added to the complexity of the heavens and confirmed the planets as 'wanderers' (the original meaning of the word).29 This quest for what the universe was made of was continued by the two main 'atomists', Leucippus of Miletus (fl. 440 BC), and Democritus of Abdera (fl. 410 BC).30 They argued that the world consisted of 'an infinity' of tiny atoms moving randomly in 'an infinite void'. These atoms, solid corpuscles too small to be seen, exist in all manner of shapes and it is their 'motions, collisions, and transient configurations' that account for the great variety of substances and the different phenomena that we experience. In other words, reality is a lifeless piece of machinery, in which everything that occurs is the outcome of inert, material atoms moving according to their nature. 'No mind and no divinity intrude into this world...There is no room for purpose or freedom.'31 Anaxagoras of Clazomenae was partially convinced by the atomists. There must be some fundamental particle, he thought: 'How can hair come from what is not hair, or flesh from what is not flesh?'32 But he also felt that none of the familiar forms of matter-hair or flesh, say-was quite pure, that everything was made up of a mixture, which had arisen from the 'primordial chaos'. He reserved a special place for mind, which for him was a substance: mind could not have arisen from something that was not mind. Mind alone was pure, in the sense that it was not mixed with anything. In 468-467 BC, a huge meteorite fell to earth in the Gallipoli peninsula and this seems to have given Anaxagoras new ideas about the heavens. He proposed that the sun was 'another such mass of incandescent stone', 'larger than the Peloponnese', and the same went for the stars, which were so far away that we do not feel their heat. He thought that the moon was made of the same material as the earth 'with plains and rough ground in it'.33 The arguments of the atomists were strikingly near the mark, as experiments confirmed more than two thousand years later. (As a theory it was, as Schrodinger put it, the most beautiful of all 'sleeping beauties'.34) But, inevitably perhaps, not everyone at the time accepted their ideas. Empedocles of Acragas (fl. 450), a rough contemporary of Leucippus, identified four elements or 'roots' (as he called them) of all material things: fire, air, earth and water (introduced in mythological garb as Zeus, Hera, Aidoneus and Nestis). From these four roots, Empedocles wrote, 'sprang all things that were and are and shall be, trees and men and women, beasts and birds and water-bred fishes, and the long-lived gods too, most mighty in their prerogatives...For there are these things alone, and running through one another they assume many a shape.' But he also thought that material ingredients by themselves could not explain motion and change. He therefore introduced two additional, immaterial principles: love and strife, which 'induce the four roots to congregate and separate'.35 As ever, we do well not to make more of Ionian positivism than is there. Pythagoras had such an immense reputation that he was credited with many things he may not have been responsible for-even his famous theorem, which may have been the work of later followers. And these first 'scientists' have been compared to a 'flotilla' of small boats headed in all directions and united only by a fascination for uncharted waters.