In most accounts of the history of physics during 1880 to 1920, Einstein's genius casts such a long shadow that the achievements of his contemporaries are hidden and, as a result, the history is oversimplified. For example, the undergraduate curriculum's introduction to Einstein's special theory of relativity typically selects the Albert Michelson-Edward Morley experiment of 1887 as the crucial pathfinder that led Einstein to his 1905 paper on special relativity. That experiment produced a null result in the quest to detect Earth's motion through the ether, the medium thought to be responsible for the propagation of light. Pedagogically, it makes sense for instructors to use this elegant experiment as the guiding light for Einstein, but he never saw it that way. He had other routes to the conclusion that the electrodynamics of his time was deeply flawed.
In Einstein's Generation, Richard Staley carefully constructs a true history of classical physics in these critical four decades. He begins with a new examination of the careers of Michelson and Einstein, the depth and breadth of which corrects numerous asymmetries that have arisen in the standard treatments of two great physicists. Michelson, America's first Nobel laureate in physics, invented interferometry, in which two monochromatic beams of light produce interference patterns. The basic phenomenon was well known, but Michelson showed how it could be developed to produce all manner of instruments.
Michelson's 1907 Nobel prize was for the invention and development of interferometry, not for the eponymous experiment. Staley attributes Michelson's early success to his engagement with the astronomical community and its instrument makers. When he began his work on interferometry, the established astronomical observatories in the US were more experienced at technical work than the physics labs that were springing up in universities. The first ether-drift experiment, which was never fully completed, was a mere sideshow to Michelson's fundamental work on measuring the speed of light.
In an age when metrology involved a medieval relic, the use of a standard metal bar, Michelson pursued an ambitious research programme to find a reproducible standard of the highest precision based on the speed of light. By the end of the 19th century, he had transformed metrology into a precision science. All of which meant that physicists in their labs came to question exactly how length and time are to be defined and then measured precisely. Einstein would show them, within five years, that such measurements are relative.
Staley makes impressive use of the 1900 World's Fair in Paris as a source of information on the standing of applied physics and technology at the time. At this event, great attention was placed on displaying the technological revolution made possible by electromotive power, the harnessing of the electron and the application of Maxwell's laws. The US firm Warner and Swasey exhibited many astronomical telescopes with finely graduated setting circles, accurate to one second of arc, a clear indication that the American astronomical community was about to pull ahead of the European observatories. The electrical technology firm owned by Einstein's family did not display in Paris because it had collapsed a few years earlier after its failure to win a bid to provide Munich with electrical lighting.
Concurrently with the World's Fair, the first International Congress of Physics convened. The French Physical Society decided that the congress would have reports and discussions on a limited number of topics decided in advance. These would include the determination and definition of units, a standard feature of international gatherings. The committee took great care with the scientific programme, announcing well in advance which papers would be read. The registration fees of 20 gold francs per attendee poured in, and nearly a thousand people attended - almost two thirds of the worldwide physics community.
The French polymath Henri Poincare, charged with producing a keynote address on the state of physics and the problems the discipline faced, warned of the need to root out dangerous hypotheses. In an extended discussion of electrodynamics, and of Hendrik Lorentz's hypothesis of length contraction by bodies in relative motion, Poincare raised the prospect that the ether must be abandoned as an unsupported hypothesis. He discussed the principle of relative motion in his 1900 papers, and named it the principle of relativity in 1904, according to which no mechanical or electromagnetic experiment can discriminate between a state of uniform motion and a state of rest. You'll not find that information in many undergraduate textbooks. Einstein, then aged just 21, was not in Paris (he was finishing his finals), but Poincare's paper was published in the leading German physics journal.
After the Paris congress, Staley turns to progress on understanding the physics of the electron. Radioactive decay gave physicists access to electrons travelling at nearly the speed of light. Although the experimentalists lacked the means to control the electrons, they were able to observe the mass of electrons and provide the first tests of Einstein's relativity. In a survey of the early Nobel prizes in physics, Staley reveals how again and again the electron featured in a wide range of fields. The electron, discovered in the Cavendish Laboratory in 1897, defined the modernity of physics at the turn of the century.
Soon after 1900, physicists focused on what Staley refers to as the sharp end of experimental research on the mass and dynamics of the electron. This gave an impetus to the importance of experiments as relativity began to be taken seriously in Germany. Einstein's reputation, and the acceptance of relativity, was driven initially by his contemporaries in Germany, such as Max Born, who could see the fundamental connections between the electron and relativity. From this observation, Staley tells us how the development of electrodynamics immediately after 1905 is, in fact, a history of relativity. The two were intertwined. And the dialogue of physics spoke of the overthrow of the classical physics - mechanics and thermodynamics, electricity and magnetism - by modernity.
Staley concludes this masterly survey with a study of the first Solvay Council, held in Brussels in 1911. Belgian-born Ernst Solvay had made his fortune manufacturing sodium carbonate, which allowed him to provide generous endowments for institutes of physiology and social science. He had a strong interest in physics and had developed a speculative approach to matter and gravitation. But in 1911 a new area took his fancy - what we now call quantum theory.
Solvay was on good terms with Walther Nernst, the low-temperature physicist who proposed the organisation of a new style of scientific conference to discuss quantum theory. The invitations went to a hand-picked group, including Einstein, Poincare, Ernest Rutherford, Max Planck and Marie Curie. There were just 21 participants at the meeting, which convened under rules of strict confidentiality, and their group photograph is the most well-known image of physicists at the turn of the century. The conference had a decisive effect in stimulating interest in the new quantum theory, the second great revolution in physics in the past century.
Einstein's Generation is a magnificent achievement and a work of great scholarship. Staley succeeds brilliantly in providing new ground for understanding how Einstein gradually emerged as the central figure within the German physics community.
Richard Staley, currently associate professor in the history of science at the University of Wisconsin-Madison, specialises in the history of physics in Europe and America during the 19th and 20th centuries, with a particular research focus on the physics community circa 1900, the development of special relativity, and the interrelations between instruments and experiments.
While studying at Cambridge, he developed an interest in meteorology, stemming from a research project on the development of experimental physics. Although Einstein's Generation is Staley's first book, he has contributed to several others.
Einstein's Generation: The Origins of the Relativity Revolution
By Richard Staley
University of Chicago Press
504pp, £57.50 and £22.50
ISBN 9780226770567 and 770574
Published 8 January 2009