The best stories in the history of physics are those in which someone comes from humble origins and, seemingly out of nowhere, makes a brilliant discovery that changes everything. Such stories, however, can give a very misleading impression of the nature of scientific progress: science is a continuous process, and a closer inspection of any incredible breakthrough always reveals that there were numerous earlier discoveries that anticipated it.He gives a nice explanation of how FitzGerald deduced the contraction from Michelson-Morley, and then how Einstein used essentially the same argument to get the same formula 16 years later. But he concludes:
A great case study of this is Einstein’s special theory of relativity, introduced in 1905. Einstein’s groundbreaking work transformed mankind’s perceptions of space and time, provided answers to puzzling problems and led directly to other major discoveries, including the harnessing of nuclear energy. However, Einstein’s revelations were preceded by some twenty years of gradual progress, during which time researchers put forth tantalizing hypotheses that came closer and closer to the truth.
One such discovery was made in 1889 by George FitzGerald. To explain a seemingly incomprehensible experimental result, he suggested that objects in motion shrink along their direction of travel. In this post, we will discuss what is now known as the FitzGerald-Lorentz length contraction and explain how FitzGerald fell short of the astonishing ideas that would be conceived by Einstein.
Herein lies the difference between the FitzGerald form of length contraction and the Einstein form. In the FitzGerald version, both the first and second observer can agree that the experiment is moving. The observer moving with the experiment would in principle be able to measure a change in the electrical forces between molecules, demonstrating a motion in the aether. In the Einstein version, the two observers agree that the speed of light is c, but disagree on the distances that the light has to travel.No, that is not a difference. Dr. SkySkull quotes the FitzGerald 1889 paper. The paper does not say that any such change in electrical forces could be measured. The Michelson-Morley experiment failed to detect any motion thru the aether, and FitzGerald did not say that any such motion was detectable.
Dr. SkySkull goes on:
Einstein’s theory represented a huge change in mankind’s perception of nature and the universe. Space and time were relegated from absolute quantities to relative ones depending on an observer’s state of relative motion. Nevertheless, others were already anticipating Einstein’s discovery before him. Lorentz, who was a proponent of the FitzGerald contraction hypothesis, also derived a mathematical transformation between observers — the Lorentz transformation — that left the speed of light constant for all observers. This transformation is now a part of Einstein’s relativity. Other scientists such as Ernst Mach and Henri Poincaré had already in the late 1800s begun to dismiss the notion of absolute space and time, and the aether along with it, and propose a new theory of relativity. In fact, one distinguished scientist stubbornly refused to accept any real significance in Einstein’s relativity work.No, Einstein had no new principle. His principles are present in that 1889 FitzGerald paper, as you can see in SkySkull's explanation. FitzGerald, Lorentz, and Poincare were much bolder than Einstein. By the time that Einstein published his explanation in 1905, it was the more conventional of the competing explanations.
Einstein, however, was the one to bring all the scattered musings of the different scientists together into a new principle of physics. Where the others were inching towards a new theory of relativity, Einstein leapt towards it wholeheartedly. It was a great discovery, but the earlier efforts of others such as FitzGerald show that Einstein’s work was part of a greater effort to understand the nature of space and time.
In a 2008 post, SkySkull calls Edmund Whittaker an anti-relativist. Obviously he hasn't read Whittaker's book, but it is very enthusiastic about special and general relativity, and is very generous in over-crediting Einstein for general relativity.
SkySkull quotes a Max Born letter to Einstein:
Whittaker, the old mathematician, who lives here as Professor Emeritus and is a good friend of mine, has written a new edition of his old book History of the Theory of the Ether, of which the second volume has already been published. Among other things it contains a history of the theory of relativity which is peculiar in that Lorentz and Poincaré are credited with its discovery while your papers are treated as less important. Although the book originated in Edinburgh, I am not really afraid you will think that I could be behind it. As a matter of fact I have done everything I could during the last three years to dissuade Whittaker from carrying out his plan, which he had already cherished for a long time and loved to talk about. I re-read the originals of some of the old papers, particularly some rather off-beat ones by Poincaré, and have given Whittaker translations of German papers (for example, I translated many pages of Pauli’s Encyclopaedia article into English with the help of my lecturer, Dr. Schlapp, in order to make it easier for Whittaker to form an opinion). But all in vain. He insisted that everything of importance had already been said by Poincaré, and that Lorentz quite plainly had the physical interpretation. As it happens, I know quite well how sceptical Lorentz was and how long it took him to become a relativist. I have told Whittaker all this, but without success. I am annoyed about this, for he is considered a great authority in the English speaking countries and many people are going to believe him.Born probably helped convince Whittaker that Einstein's special relativity papers were less important. Everyone who reads and understands those old papers comes to conclusion that Lorentz and Poincare had the whole theory before Einstein.