ABSTRACT
Aristotle (384-322 B.C.E.) taught that the ether was a fifth element that carried the stars and planets embedded in it. Plato (428-348 B.C.E.) and the Stoics regarded it as a fluid and the source of life. During the sixteenth century, Aristotle’s account was attacked, first by substituting the Stoic view and later by introducing new kinds of ether. Both René Descartes (1596-1650) and Isaac Newton (1642-1727) employed ethers as central features of their cosmologies. Seventeenth-and eighteenth-century scientists adopted ethers as working fluids in physics and chemistry,
In antiquity, the substance of the heavens was known as ether, although there was no general agreement on its nature or extent. When Aristotle adopted Eudoxus of Cnidus’s construction to explain planetary motion, he began a tradition that treated the substance of the heavens as a series of shells surrounding a central earth. He regarded the substance of these shells as a fifth element, distinct from the four terrestrial elements and possessing a natural tendency to move at uniform speed in a circle. The stars and the planets (including the Sun and the Moon) did not move freely. They were merely denser parts of one particular shell, and their motions were the result of the rotation of that shell and the rotation of other shells to which it was attached at its axes.
