In his 1989 book "Relativitaetstheorie - aktuell" (Relativity Theory - an Update), published by BSB Teubner in Leipzig, Germany, the physicist Ernst Schmutzer of Jena, Germany, writes on page 42: "The so called Michelson experiment, conducted by Michelson in Potsdam in 1881, stands out among a series of many pre-relativity attempts [to prove the existence of the luminiferous ether]. Its results irrevocably shook the ether hypotheses. Later, with improved technology, the experiment was repeated by E.W. Morley (1897) and D.C. Miller (1904) as well as K.K. Illingworth and G. Joos (1927 - 1930 at the Zeiss Works in Jena). This decidedly hardened the conclusiveness of the first experiment. Because this is one of the most important experiments regarding the Theory of Special Relativity (SR), we shall sketch out the experiment and draw a few relevant conclusions."
"Fig 3" follows. "Fig. 3 shows schematically a Michelson interferometer which shall be fixed on Earth and, therefore, moves relative to the Luminiferous Ether, whose existence we presume for the experiments conceptualization in order to demonstrate its absurdity."
On page 44 we then read: "Subsequently the Michelson experiment was repeated frequently, particularly employing advances in laser physics during more recent years. The result was always negative." This "negative" refers to the hypotheses of the luminiferous ether in which light was supposed to be propagating. This is why A. Einstein proposed to drop the ether hypothess. Based on the consistent and unequivocal results of the so called "Michelson experiment", which by today's standards would be regarded as a simple light test, one would think that the experiment went beyond the call of duty to show the absurdity of the ether. These facts notwithstanding E. Schmutzer states that it is "one of the most important experiments for the Theory of Special Relativity", a statement we keep running into whenever the necessity of Einstein's Theory of Special Relativity is being argued.
Yet, what reasons for SR does the so called Michelson experiment and its results provide???
Or, posing the question differently: What about the experiment does remain unexplained, once we bite the bullet and learn from it to drop the ether hypotheses - even though we might have to give some thought to the basics of optics??? What is it that SR explains more or better, especially as it requires a strong hypotheses, namely the relativity of time and space, while the non-existence of the ether makes it particularly superfluous? Or was this simplest - and most appropriate to the experiment - explanation wrong or incomplete? I don't think so.
The process, after all, was the following: The light source L and the light target F (for "Fernrohr" = German for telescope) were part and parcel of one system "firmly connected to the Earth". The light beam, split by a semi-transparent mirror into two mutually perpendicular directions, traversed equal distances in equal times between L and F, so that both partial beams, redirected toward the light receiver F, arrived there at the same time, although one partial beam had earlier moved in the direction of the Earth's orbit. What of this result - that light in reference to its source propagates equally fast in all directions - does still call for an explanation - except that a light path influencing ether obviously does not exist?
Only an infraction of isotropy would have demanded an explanation, e.g. an infraction of isotropy by virtue of an ether more or less rigidly tied to the sun. This is because each thing remains in its once acquired state, including light in its motion as it propagates from its source. The design of the experiment was, correctly, based on this premise and it would not have made any sense otherwise. (Premises of physical research can not, in turn, be subject of explanation by physics). So, where is the physics problem here? Didn't Einstein say he tries to explain everything as simply as possible, yet without undue simplification?
Therefore, I would be grateful for some enlightenment on what it is about the isotropy of light propagation that needs explaining, or what convictions were, or still are, standing in the way of its acceptance.
I like to emphasize: This is not about the question if or if not a theory of relativity is needed, but about the question if or if not the so called Michelson experiment needs a relativistic explanation. Maybe pondering this question leads us to views whose existence and/or justifications we have, as of yet, not considered.
Einstein's Question:
"Why is it that people always chit-chat about my theory of relativity? After all, I did other useful work - maybe even better. But the public doesn't take notice of that at all."
(Albert Einstein, quoted by C. Selig, "Albert Einstein. Leben und Werk eines Genies unserer Zeit", Europa Verlag, Zurich 1960, page 336; also "Albert Einstein - Worte in Zeit und Raum" published and with an introduction by Sigurd M. Daecke, Verlag Herder, Freiburg im Breisgau 1991, page 103)
My response to Einstein:
People "chit-chat" again and again about the Theory of Relativity because they feel obliged to understand it. Put down by Einstein as "chit-chat", their effort is the honest attempt of decent and educated citizens to make sense of his theory, i.e., to find some rational access to it. But because there is no such thing, in their predicament people think of Einstein as a genius that can't be caught up with.
translation by Walter G. Hecker (Silicon Valley/California/USA)