Luminous Ether: A Modern Physics Reality that Failed

Luminous Ether

In 1864 James Clerk Maxwell discovered the basic equations that govern electricity and magnetism and he also said that both these phenomena correspond to a single entity known as the Electromagnetic field. That was the first step that was taken towards the unification of fields and physicists, even today, are doing their best to combine all of the physical laws into a single entity – The Theory of Everything. Maxwell was the first one to show that the task of unification is not futile.

From his theory, Maxwell discovered that the waves in the electromagnetic field travel at the same speed as that of light. He said that light itself was an electromagnetic wave of a particular frequency. This bold statement of Maxwell was later confirmed by the experiments of Heinrich Hertz.

The Beginning

All the known physical waves vibrate in some medium (air, water etc). So it was assumed that the light must also have some medium through which light propagates. This medium was given the name “luminiferous ether”. Many physicists, at that time, gave special attention to the study of the properties of this “ether”.

Maxwell described the subject of this research, in his own words, as “whatever difficulties we may have in forming a consistent idea of the contribution of the ether, there can be no doubt that the interplanar and interstellar spaces are not empty but are occupied by a material substance or a body, which is certainly the largest and most probably the most uniform body of which we have any knowledge”.

Many physicists tried to infer the hypothetical properties of this medium. Since light travels so fast, the elasticity of the medium should be enormous. Since light is a transverse wave, the medium can only be solid and it should have a complex structure as it cancels out the longitudinal propagation. Although the world was filled with a transparent “glass” much harder than steel, this “glass” does not offer even the slightest resistance to the passage of material bodies. Some physicists proposed that the ether behaved as solid for the rapid motions as that of light and for material bodies like earth, it behaved like a fluid, in the manner of certain wax-like solids with deformation-rate dependent viscosities.

The Michelson-Morey Experiment

In 1887, Michelson and Morley prepared a setup to find the velocity of the Earth with respect to the “ether”. They set up an optical racetrack that pitted a light beam moving north and south between two parallel mirrors against an east-west travelling beam. The idea was that the ether wind will give one of the tracks an advantage and this one was certain to win. But no such victory was observed, the experiments could detect no movement of the luminous ether through the Earth.

Michelson and Morley’s failure to detect the “ether-wind” led physicists to propose that heavy bodies like Earth trap the ether and carry it along with them. However, attempts to detect such a phenomenon failed. To explain the failure of the Michelson Morley experiment, some physicists invoked the phenomena of “ether-squeeze” It proposed that the motion through ether resulted in a tiny contraction of all physical bodies in the direction of the motion. It said that the light beam would have lost the race would now have to travel a shorter distance due to the squeeze. This was a desperate attempt to save the appearances of the ether.

Although the properties of the ether grew preposterous with each new investigation, no one ever questioned the existence of the ether.

Einstein’s Contribution to the Luminous Ether

In 1905, Albert Einstein published a new theory of space and time. This theory said that only relative motions were of any consequence for the basic laws of physics. There is no physical means by which one can know the absolute motion of any body through space.

In his theory, although space-time were relative concepts, certain other physical quantities were absolute and all the theories are to be made out of these physical quantities alone. Only this way, the laws can be the same for all observers.

One of Einstein’s absolute quantity was the speed of light and the other was the space-time interval. Although space and time were themselves relative, a certain quantity, i.e. the space-time interval made out of them was absolute. This gave rise to the notion that our world is a four-dimensional world, consisting of three spatial dimensions and one time dimension.

The luminous ether, a body that is “standing still in space” violates a quantity to be used as an absolute because it has different speeds when measured from different reference points which are themselves relative. If Einstein’s theory was correct, which was experimentally verified later, the concept of ether can never be a physical law. The luminous ether plays no part whatsoever in modern physics. The ether is a reality that failed.

Luminous Ether