Abstract

In the sixth century BCE Ionian philosophers explained the sun as a mass of fire, sometimes as floating like a leaf or a cloud above the earth. It was thought to be fueled by moist vapors from the earth. In the f i f t h century philosophers typically envisaged the sun as a red-hot stone or a molten mass carried around by the force of a cosmic vortex. The decisive shift in explanations seems to result from the cosmology of Parmenides, who recognized that the moon received its light from the sun, and hence inferred that the heavenly bodies were spherical solid bodies. The new theory required a new account of how the sun came to be hot. The sun was said to be heated either by being in a fiery region or by friction. The discovery of a large meteorite seemed to confirm the fifth-century theory.