Warped Passages - Lisa Randall [44]
In fact, Einstein himself initially thought of special relativity merely as an improvement on Newtonian physics—not as a radical paradigm shift. This, of course, grossly underplays the ultimate significance of his work.
Special Relativity
A very reasonable thing to expect from physical laws is that they should be the same for everyone. No one could blame us for questioning their validity and utility if people in different countries or sitting on moving trains or flying on an airplane experienced different physical laws. Physical laws should be fundamental and hold true for any observer. Any differences in calculations should be due to differences in environment, not the physical laws. It would be very strange indeed to have universal physical laws that required a particular vantage point. The particular quantities you might measure could depend on your reference frame, but the laws that govern these quantities should not. Einstein’s formulation of special relativity ensures that this is the case.
In fact, it’s somewhat ironic that Einstein’s work on gravity is referred to as “the theory of relativity.” The essential point that drove both special and general relativity was that physical laws should apply for everyone, independent of their reference frame. In fact, Einstein would have preferred the term Invariantentheorie.* In a letter Einstein wrote in 1921 in reply to a correspondent who had suggested he reconsider the name, he admitted that the term “relativity” was unfortunate.† But by that time, the term was too well entrenched for him to attempt to change it.
Einstein’s first insight about reference frames and relativity came from thinking about electromagnetism. The well-known theory of electromagnetism from the nineteenth century was based on Maxwell’s laws, which describe the behavior of electromagnetism and electromagnetic waves. The laws gave correct results, but everyone initially falsely interpreted the predictions in terms of the motion of an aether, a hypothesized invisible substance whose vibrations were supposed to be electromagnetic waves. Einstein realized that if there were an aether, there would also be a preferred observational vantage point, or frame of reference: the one in which the aether is at rest. He reasoned that the same physical laws should apply to people who are moving at constant velocity* with respect to each other and with respect to someone at rest—that is, in frames of reference that physicists refer to as inertial frames. By requiring that all physical laws, including those of electromagnetism, should hold for observers in all inertial reference frames, Einstein was led to abandon the idea of the aether and, ultimately, to formulate special relativity.
Einstein’s theory of special relativity, with its radical revision of the concepts of space and time, was a major leap. Peter Galison,† a physicist and historian of science, suggests that it was not only the aether theory that put Einstein on the right track, but Einstein’s job at the time. Galison reasoned that Einstein, who grew up in Germany and worked at the patent office in Bern, Switzerland, must have had time and time coordination on his mind. Anyone who has traveled in Europe knows that precision is valued highly in countries such as Switzerland and Germany, which has the happy consequence that passengers can count on the trains to run on time. Einstein worked in the patent office between 1902 and 1905, during an era when train travel was becoming increasingly important, and coordinating time was at the forefront of new technology. In the early 1900s, Einstein was very likely thinking about real-world problems, such as how to coordinate the time at one train station with that at another.
Of course, Einstein