Ether was seen until the beginning of the 20th century as the material intermediate that allowed the propagation of light and other electromagnetic radiation.
In the 17th century, Christiaan Huygens had already found that light shows interference and is therefore a wave phenomenon or vibration. Interference was well understood by sound (a wave in air) and in waves in the water surface. It is therefore obvious that one asks what is going on. Indeed, in a mechanical world view, vibration requires a resilient medium to move. This medium was called aether or ether. These intermediates were recognized as resilience (elasticity) and absolute rest (standstill). The ether penetrated all the dust and filled the space between the atoms.
Einstein's relativity theories showed that the ether did not exist: the vacuum can obviously lead light, the emptiness gained the function of the former ether. Michelson-Morley-experiment
Albert Michelson and Edward Morley attempted to demonstrate the ether with their famous interferometer experiment (1887) by showing that light would move at different speeds in directions parallel to and across the earth's path around the sun, because the Earth should move through the ether. With the measurement one could also determine the absolute velocity of the earth through the universe. The experiment failed: the light speed was exactly the same in every direction and at any time of the year.
If one still wanted to hold on to the ether, one should take back the medieval geocentric model of the universe: the earth as the stationary center of the universe around which the rest of the universe turned. This was contrary to the scientific paradigm at that time. Theory of relativity
In 1905 the publication Zur Elektrodynamik bewegter Körper (About the electrodynamics of moving bodies) of Albert Einstein appeared. In this, Einstein assumed the fact that electromagnetic vibration in vacuum, measured in all directions from each object, even from a moving object, has exactly the same speed. This had very strange consequences. The publication led to other ideas about space, time and propagation of light; the need to postulate the existence of an ether actually came to an end. However, it has not been proven that the ether could not exist. On May 5, 1920, Einstein gave a lecture at Leiden University (under the title "Äther und Relativitäts-Theorie"): "Aether and Relativity" in which he said:
According to Einstein, it is therefore inevitable to assign physical qualities to space. But where matter consists of parts that can be followed in time, space time as described by general relativity can not. Concepts such as 'move' or 'standstill' are in principle not applicable. Ether as imagery at the broadcasting
On theoretical grounds, it was later shown that electromagnetic waves had the speed of light. From this it was concluded that light was also an electromagnetic wave. Originally, it was assumed that for radio and television signals transmitted by electromagnetic waves with a lower frequency than light, the ether acted as medium. In speech usage, this is still used: the ether that broadcasts the radio and television signals. As in the phrase "a radio program to send the ether".
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