One of the great questions of science in the late nineteenth century was to understand in which way the waves electromagnetic waves propagated, as it was inconceivable to admit that these waves did not have a means of propagation. Therefore, at the time, it was assumed that the luminiferous ether it was the place of propagation of electromagnetic waves.
Possible characteristics of luminiferous ether
O luminiferous ether it would be a kind of infinite fluid, thinner than lighter gases, perfectly elastic, invisible, undetectable and that would fill the universe in its entirety, both the interplanetary spaces and the intermoleculars. With the current understanding of science we have today, to admit the existence of this material would be madness. However, we need to understand that scientific truths are dated, that is, their validity is limited to what science itself assumes as truth. In the nineteenth century, the luminiferous ether it needed to be accepted as a truth.
Albert Michelson and Edward Morley Experiment
Between the years 1880 and 1890, Albert Michelson and Edward Morley used a device called an interferometer to more accurately measure the value of speed of light. The interferometer has a semi-reflective mirror that has the function of separating a ray of light into two other equal rays, allowing the passage of a little light and reflecting the other part. These split beams of light hit two mirrors, where they are reflected and meet again, hitting a detector. From the interference phenomenon, when two waves meet, it is possible to determine whether or not there was a decrease in the speed of any of the reflected beams. If by chance there is this decrease, logically it would occur because of some element that would be interfering in the light path. This element in question could only be the luminiferous ether.
Michelson and Morley failed to detect differences between the paths taken by the reflected light rays, which proved the inexistence of ether. However, they never stopped believing in this miraculous element. In 1907, Albert Michelson received the Nobel Prize in Physics not for having “proved” the non-existence of luminiferous ether, but for having developed precision optical instruments for calculating the speed of the light.
At that time, scientists needed to resolve an inconsistency, as the luminiferous ether was considered the absolute reference of the universe and the speed of light was assumed to be constant. This was a problem for Physics at the time because, if the ether is the absolute reference and the light sources in the universe move in directions and different senses, how could the speed of this electromagnetic wave be constant, given the idea of relative motion between bodies? The explanation for such inconsistency came from the understanding that the ether does not exist and with the Theory of relativity restricted by Albert Einstein.
By Joab Silas
Graduated in Physics
Source: Brazil School - https://brasilescola.uol.com.br/fisica/a-questao-eter-luminifero.htm