Ether

Late nineteenth-century hypothesis suggested by physicists as a means of accounting for the propagation of light as a wave motion through otherwise empty space. The idea of ether meshed with the teachings of the mesmerists and Theosophists, who spoke of subtle substructures of matter sometimes referred to as koilon—all-pervading, filling all space, and interpenetrating all matter. Ether was supposedly of very great density, 10,000 times more dense than water and with a pressure of 750 tons per square inch.

According to Theosophical teaching, ether was said to be capable of being perceived only by clairvoyants with the most highly developed powers. It was said to be filled with an infinitude of small bubbles, much like the air bubbles in treacle or some other viscid substance. The bubbles were supposedly formed at some ancient time by the infusion of the breath of the Logos into the ether. Of these bubbles—not of the ether— matter was said to be built, its density varying with the number of bubbles combined to form each objects.

Ether became the subject of one of the more famous experiments in physics, by Albert Abraham Michelson and E. W. Morley. Their experiment involved the splitting and reintegration of a light wave in such a manner that the presence of ether would slow one of the waves. They disproved the existence of ether and brought America its first Nobel Prize for physics. The experiment also contributed to the development of Einstein's theory of relativity. The abandonment of ether by science led to its eventual abandonment by Spiritualists and Theosophists.