Faraday’s law of induction said that the motion of the magnet through the ether created an electric field. In the second case, Lorentz’s force law said a current was created by the motion of the conducting coil through the magnetic field. “The idea that these two cases should essentially be different was unbearable to me,” Einstein said. 16
Einstein had been wrestling for years with the concept of the ether, which theoretically determined the definition of “at rest” in these electrical induction theories. As a student at the Zurich Polytechnic in 1899, he had written to Mileva Marithat “the introduction of the term ‘ether’ into theories of electricity has led to the conception of a medium whose motion can be described without, I believe, being able to ascribe physical meaning to it.” 17 Yet that very month he was on vacation in Aarau working with a teacher at his old school on ways to detect the ether. “I had a good idea for investigating the way in which a body’s relative motion with respect to the ether affects the velocity of the propagation of light,” he told Mari.
Professor Weber told Einstein that his approach was impractical. Probably at Weber’s suggestion, Einstein then read a paper by Wilhelm Wien that described the null results of thirteen ether-detection experiments, including those by Michelson and Morley and byFizeau. 18 He also learned about the Michelson-Morley experiment by reading, sometime before 1905, Lorentz’s 1895 book,
Attempt at a Theory of Electrical and Optical Phenomena in Moving Bodies.
In this book, Lorentz goes through various failed attempts to detect the ether as a prelude to developing his theory of contractions. 19
“Induction and Deduction in Physics”
So what effect did the Michelson-Morley results—which showed no evidence of the ether and no difference in the observed speed of light no matter in what direction the observer was moving—have on Einstein as he was incubating his ideas on relativity? To hear him tell it, almost none at all. In fact, at times he would even recollect (incorrectly) that he had not even known of the experiment before 1905. Einstein’s inconsistent statements over the next fifty years about the influence of Michelson-Morley are useful in that they remind us of the caution needed when writing history based on dimming recollections. 20
Einstein’s trail of contradictory statements begins with an address he gave in Kyoto, Japan, in 1922, when he noted that Michelson’s failure to detect an ether was “the first path that led me to what we call the principle of special relativity.” In a toast at a 1931 dinner in Pasadena honoring Michelson, Einstein was gracious to the eminent experimenter, yet subtly circumspect: “You uncovered an insidious defect in the ether theory of light, as it then existed, and stimulated the ideas of Lorentz and Fitzgerald, out of which the Special Theory of Relativity developed.” 21
Einstein described his thought process in a series of talks with the Gestalt psychology pioneer Max Wertheimer, who later called the Michelson-Morley results “crucial” to Einstein’s thinking. But as Arthur I. Miller has shown, this assertion was probably motivated by Wertheimer’s goal of using Einstein’s tale as a way to illustrate the tenets of Gestalt psychology. 22
Einstein further confused the issue in the last few years of his life by giving a series of statements on the subject to a physicist named Robert Shankland. At first he said he had read of Michelson-Morley only
after
1905, then he said he had read about it in Lorentz’s book
before
1905,and finally he added, “I guess I just took it for granted that it was true.” 23
That final point is the most significant one because Einstein made it often. He simply took for granted, by the time he started working seriously on relativity, that there was no need to review all the ether-drift experiments because, based on his starting assumptions, all
Einstein had been wrestling for years with the concept of the ether, which theoretically determined the definition of “at rest” in these electrical induction theories. As a student at the Zurich Polytechnic in 1899, he had written to Mileva Marithat “the introduction of the term ‘ether’ into theories of electricity has led to the conception of a medium whose motion can be described without, I believe, being able to ascribe physical meaning to it.” 17 Yet that very month he was on vacation in Aarau working with a teacher at his old school on ways to detect the ether. “I had a good idea for investigating the way in which a body’s relative motion with respect to the ether affects the velocity of the propagation of light,” he told Mari.
Professor Weber told Einstein that his approach was impractical. Probably at Weber’s suggestion, Einstein then read a paper by Wilhelm Wien that described the null results of thirteen ether-detection experiments, including those by Michelson and Morley and byFizeau. 18 He also learned about the Michelson-Morley experiment by reading, sometime before 1905, Lorentz’s 1895 book,
Attempt at a Theory of Electrical and Optical Phenomena in Moving Bodies.
In this book, Lorentz goes through various failed attempts to detect the ether as a prelude to developing his theory of contractions. 19
“Induction and Deduction in Physics”
So what effect did the Michelson-Morley results—which showed no evidence of the ether and no difference in the observed speed of light no matter in what direction the observer was moving—have on Einstein as he was incubating his ideas on relativity? To hear him tell it, almost none at all. In fact, at times he would even recollect (incorrectly) that he had not even known of the experiment before 1905. Einstein’s inconsistent statements over the next fifty years about the influence of Michelson-Morley are useful in that they remind us of the caution needed when writing history based on dimming recollections. 20
Einstein’s trail of contradictory statements begins with an address he gave in Kyoto, Japan, in 1922, when he noted that Michelson’s failure to detect an ether was “the first path that led me to what we call the principle of special relativity.” In a toast at a 1931 dinner in Pasadena honoring Michelson, Einstein was gracious to the eminent experimenter, yet subtly circumspect: “You uncovered an insidious defect in the ether theory of light, as it then existed, and stimulated the ideas of Lorentz and Fitzgerald, out of which the Special Theory of Relativity developed.” 21
Einstein described his thought process in a series of talks with the Gestalt psychology pioneer Max Wertheimer, who later called the Michelson-Morley results “crucial” to Einstein’s thinking. But as Arthur I. Miller has shown, this assertion was probably motivated by Wertheimer’s goal of using Einstein’s tale as a way to illustrate the tenets of Gestalt psychology. 22
Einstein further confused the issue in the last few years of his life by giving a series of statements on the subject to a physicist named Robert Shankland. At first he said he had read of Michelson-Morley only
after
1905, then he said he had read about it in Lorentz’s book
before
1905,and finally he added, “I guess I just took it for granted that it was true.” 23
That final point is the most significant one because Einstein made it often. He simply took for granted, by the time he started working seriously on relativity, that there was no need to review all the ether-drift experiments because, based on his starting assumptions, all
Similar Books
