The Origin of Relativity

For more than half a century, textbooks have hailed an 1887 experiment performed by the American scientists Albert A. Michelson and Edward W. Morley as the inspiration for Einstein's 1905 Special Theory of Relativity. The two Americans showed that the speed of light is constant despite the motion of its source, a puzzling result that defied the Newtonian physics of the time, but was later explained by Einstein's equations. Yet was Einstein actually guided toward his epochal achievement by the Michelson-Morley experiment? After combing the Einstein archives at Princeton, Physicist-Historian Gerald Holton concludes that the answer is no.

When Einstein died in 1955, he left 25 cabinets filled with personal memorabilia. These documents, Holton writes in the American Journal of Physics, include a number of letters in which Einstein speaks of the influence of the experiment on the formulation of his theory: this influence is always described in such words as "negligible," "rather indirect" or "not decisive." Furthermore, toward the end of his life, Einstein appears to have become increasingly determined to demolish the myth. In an unpublished letter written only a year before his death, Einstein said: "I even do not remember if I knew of [the experiment] at all when I wrote my first paper on the subject."

Then how did the misconception arise? In part, says Holton, because of Einstein's own generous tributes to Michelson and Morley, whose work--in retrospect--provided the only experimental confirmation of relativity for many years. But most of the blame rests with the scientific community itself. By trying to fit the evolution of one of the most important scientific concepts of the 20th century into a neat logical sequence, Holton says, textbook writers (himself included) have nurtured what he calls the "experimenticist fallacy": the false notion that theory always flows directly from experiment. In the process, he says, they do not fully recognize the extraordinary intellectual daring of Einstein's equations, and also ignore the great scientist's own explanation of their origin: "There is no logical way to the discovery of these elementary laws. There is only the way of intuition."

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