In the late 19th century, physicists postulated that aether permeated all throughout space, providing a medium through which light could travel in a vacuum , but evidence for the presence of such a medium was not found in the Michelson—Morley experiment , and this result has been interpreted as meaning that no such luminiferous aether exists. In Greek mythology , it was thought to be the pure essence that the gods breathed, filling the space where they lived, analogous to the air breathed by mortals. Aristotle , who had been Plato's student at the Akademia , agreed on this point with his former mentor, emphasizing additionally that fire has sometimes been mistaken for aether. However, in his Book On the Heavens he introduced a new "first" element to the system of the classical elements of Ionian philosophy. He noted that the four terrestrial classical elements were subject to change and naturally moved linearly. The first element however, located in the celestial regions and heavenly bodies, moved circularly and had none of the qualities the terrestrial classical elements had. It was neither hot nor cold, neither wet nor dry. With this addition the system of elements was extended to five and later commentators started referring to the new first one as the fifth and also called it aether , a word that Aristotle had not used. Aether differed from the four terrestrial elements; it was incapable of motion of quality or motion of quantity.
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Ether , also spelled aether, also called luminiferous ether , in physics , a theoretical universal substance believed during the 19th century to act as the medium for transmission of electromagnetic waves e. The ether was assumed to be weightless, transparent, frictionless, undetectable chemically or physically, and literally permeating all matter and space. The theory met with increasing difficulties as the nature of light and the structure of matter became better understood. It was seriously weakened by the Michelson-Morley experiment , which was designed specifically to detect the motion of Earth through the ether and which showed that there was no such effect. Ether theories were also used to explain gravity beginning in the 17th century, but they did not have the popularity of those explaining the propagation of light. Info Print Cite. Submit Feedback. Thank you for your feedback. The Editors of Encyclopaedia Britannica Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree
Also known as ether , the definition of the aether from dictionary. Numerous experiments following Michelson-Morley, with greater precision instruments, have also been unable to detect the aether. Following this experiment, scientists including Albert Einstein, Max Planck, Neils Bohr and other famous physicists in the s had to build their theories and equations based on an assumption that there is no medium capable of propagating a wave in space. The aether is a critical, missing component of physics that must be considered to explain the wave nature of matter.