Contrary to popular belief in the United States, Einstein did not operate in a scientific vacuum, and his time as a patent “clerk” in Bern was not a dead-end that was a complete waste of his talents and abilities. At least that is the opinion of Peter Galison’s Einstein’s Clocks, Poincare’s Maps. Focusing on the time period between 1890 and 1910, Galison examines the role of developments in coordinated time theory, the impact of France’s Ecole Polytechnique on research methods, and the training Einstein received in the patent office in the development of his theory of special relativity. At the same time, Galison places both the adoption of standard measurements for time, space and geography in the context of late 19th century international politics and traditions of European scientific thought.
Although it is disguised in biographical studies of Henry Poincare and Albert Einstein, Galison’s real target seems to be the development of the theory of special relativity, which he ultimately attributes to Einstein. Although he credits Einstein with the discovery, Galison repeatedly states that the theory was the outgrowth of physics research involving electromagnetic fields and time coordination efforts of cities, railroads, and nations. In this respect, the biographical treatment of Einstein and Poincare is merely a tool that provides understanding of the main topic. This is not to imply that Einstein and Poincare are an afterthought, rather they are the main characters in a story that involves them, but is not about them.
The reason Galison takes this tack is that it provides the most accessible method for discussing the development of the theory of relativity in the greater context of scientific inquiry and the pressures of international competition over weights and measures, universal time standards, and the location of the prime meridian. However, at times, Galison focuses so much on these issues that it is easy to lose sight of Einstein, Poincare, and relativity. It can be argued that Galison provides so much background and historical context that it overwhelms the reader with excessive amounts of detail.
Galison chooses Einstein as one of his two speakers on the topic of coordinated time and relativity simply because it was Einstein’s 1905 paper “On the Electrodynamics of Moving Bodies” that signaled the change from an emphasis on classical mechanics in the study of physics to a new theoretical-practical model. Poincare, on the other hand, is chosen as the foremost practitioner of the practical mechanical philosophy, and a product of the foremost school of engineering in Europe. The contrast between the scientific philosophies of the two men allows Galison to illustrate the profound significance of the change represented by Einstein’s theory of special relativity, and is easiest to illustrate biographically.
Before leaping into the intricacies of international relations, the training of engineers, or the workings of Swiss patent offices, Galison takes the time to explain Einstein’s theory of special relativity and how it was different from prevailing thought on how electromagnetic fields work. In 1905, when Einstein introduced the theory of special relativity, most physicists believed that light waves moved through some unknown substance as waves in the ocean or sound waves through the air. Unable to quantify the unknown media light moved through, 19th century physicists dubbed it ether, and hoped that eventually they would be able to identify it empirically. The problem with using ether to explain physical phenomena went beyond merely being unable to quantify it or study its effects; it required that identical events require multiple explanations depending on minimal changes in the experiment. The example Einstein used to introduce his theory was that under the old classical mechanics methodology using ether, the electricity generated in a coil when near a magnet was explained differently depending on whether the coil moved toward the magnet, or the magnet moved closer to the coil. Einstein believed that there should be a single explanation for the electrical field generated regardless of whether the coil or magnet moved, and he blamed the requirement for separate explanations on physicist’s insistence that ether existed.
Einstein’s solution was to dispose of the ether entirely. He did this for two reasons. First, he believed that there should be a single explanation for what he saw as a single problem, and second, because the existence of ether could not be demonstrated empirically. Without any proof of ether’s existence, Einstein saw no reason to jump through scientifically questionable hoops to account for it. This led him to the postulate that there was “no way to tell which unaccelerated reference frame was at rest”, which meant that physical objects that were not accelerating behaved independently of the reference frame they occupied. This new principle of relativity is interesting not only in the impact it had on 20th century scientific understanding, but that Galileo had noted that when at sea in smooth waters, experiments, such as ball drops, behaved in the same manner they did on land. As Galison puts it, “There was simply was no way to use any part of mechanics to tell whether a room was ‘really’ at rest or ‘really’ moving.” The general idea behind the theory of relativity was understood for at least three hundred years before Einstein published his paper.
Relativity enters into Galison’s broader topic due to Einstein’s extension of it to the speed of light. Einstein contended that the speed of light was always exactly the same, regardless of the speed of the source relative to the observer. What this meant was that rather than light moving at 300,000 kilometers per second + the speed of the source, light always moved at exactly 300,000 kilometers per second. This impacted physicists’ conception of simultaneity, which in turn affected ideas of how the coordination of disparately located clocks should be done. Einstein insisted that the concept of simultaneity be defined procedurally, saying that just because he received to signals at the same moment did not mean they were sent at the same moment if the signals traveled different distances. Einstein demonstrated the solution using a clock coordination scenario, which was particularly apt given the importance of clock coordination for the running of trains and the prestige of governments. Einstein’s procedure for clock coordination said that users should have, “one observer at the origin A send a light signal when his clock says 12:00 to B at a distance d from A; the light signal reflects off B and returns to A. Einstein has B set her clock to noon plus half the round trip time.” If the speed of light remained the same in any direction, then it could be used to determine trip time so that clocks could be easily coordinated over large distances.
In isolation, Einstein’s theory, even with its deliberate inclusion of a procedure for time coordination, could have been significant only to scientists. However, Galison points out that it had an almost immediate impact on time coordination, which stretched along rail lines and across oceans, due to the research of James Clerk Maxwell. A Cambridge physicist, Maxwell developed a theory that “showed light to be nothing more than electric waves.” This allowed Einstein’s theory of relativity to have an immediate impact as railroads and telegraph stations used electricity to coordinate their clocks.
The immediate applicability of the theory of relativity to clock coordination highlights two issues of international concern at the turn of the 20th century, which Galison concentrates heavily on. The first issue was the development of standard units of measure for both weight and distance. After diplomatic maneuvering the honor of creating, distributing, and storing the standard meter and kilogram fell to France, which painstakingly created the copies to be held by other nations and kept the originals and “witnesses” in carefully protected vaults. The second issue was of standardized, universal time, and it was much more difficult to resolve.
Galison discusses in detail the task of laying undersea telegraph cables, which were used both for communication, but also for mapping and time coordination. While the use of the cables for time coordination is an immediately obvious use of the cables given Einstein and Maxwell’s work, their use for mapping is not so intuitive. Both mapping and time coordination were prerequisites for the adoption of universal time standards.
Mapping comes into the equation because of the difficulty of mapping accurate longitude lines. Longitudinal calculation requires extremely precise measurement of time, a task that was near impossible with the chronometers available for rail and shipboard use. Laying undersea telegraph cables, which could be used for time coordination, also allowed cartographers to determine extremely precise calculation of the longitude of the receiving stations. While this solved the problem of determining exactly where any geographic location was in relation to another, it did not solve the issue of where to start counting longitude from, which was a political issue.
For the public, the solution to the international political dispute over where the prime meridian should be located is what makes Einstein’s theory of special relativity relevant. This dispute, which focused on whether the prime meridian, or longitude of zero degrees, should be at Greenwich, England, or Paris, France, was ultimately decide by the United States’ adoption of standardized time zones based on Greenwich as the zero line and England’s dominant role in overseas shipping. Of course, Galison does not immediately leap to this conclusion, and continues to discuss the lives and training of both Poincare and Einstein after discussing it, but this is the essence of Einstein’s Clocks, Poincare’s Maps. As he says himself, his work is the story of the development time coordination, and the adoption of a universal time standard represents the ultimate in time coordination, which is ultimately the legacy of Henri Poincare and Albert Einstein.