Anaximenes Says Stars Burn

Anaximenes of Miletus (active around 545 B.C.E.) theorized that what he called aer (air or vapor) was the most basic form of matter and was also the substance that formed the life spirit of animals, the soul of humankind, and the divine essence of the gods. He also believed that, when rarified, aer turned to fire, and he held that the sun, moon, and stars were collections of rarified aer, masses of fire, which, he believed, were set into a great crystal hemisphere.