Today it is possible to pull out your telephone and know immediately where you are and what time it is, so the prospect of, say, setting one’s watch by Immanuel Kant’s daily walk seems intrinsically absurd. Yet, before the turn of the century, it was not unusual for the time in one town to be very different from the time in the next town down the road, and the only unification of clocks came from the local rail line. Lacking a global idea of time, our knowledge of longitude was uncertain, so much so that cartographers could not pin down even the distance between London and Paris, much less that between the Americas and Europe. Our transit from “here there be dragons” to your iPhone’s GPS function owes much to French mechanist Henri Poincaré and physicist Albert Einstein, contributions Peter Galison examines in his book Einstein’s Clocks, Poincaré’s Maps [Amazon].
Einstein comes first in the title, but it is clear from early on that Galison’s real interest is in Poincaré. Most Americans have an opposite preference, and it’s easy to understand why. Einstein’s peregrinations and iconoclasm speak to certain American sensibilities. Poincaré, by contrast, was French, and fiercely so, a student of the École Polytechnique, a member of many Academies and Societies, and an important member of the Bureau of Longitude.
That last may seem faintly hilarious, now, but at that time the determination of longitude was no small task. One of the first tasks of the mighty transatlantic telegraph cables was to fix the time of events at two distant spots, thus determining the longitudinal difference between them. Following on the international adoption of the metric system, the French hoped to have the Prime Meridian fixed to Paris, where the meter, kilogram, and associated measures lay. Poincaré even became involved in an effort to create a metric system of time. Rather than bothering much with Relativity, Galison devotes most of the book to examining the multiple levels where one if its key insights (the synchronization of clocks) played a role. As he puts it:
In to the precision swing of master clock pendulums, out to the undersea telegraph cables crisscrossing the oceans. In to follow the minutiae of individual train schedulers, jewelers, and astronomers; then back out to the legal recalibration of national and world-covering time zones. In this process of scrutiny, historical light necessarily plays off the very different scales utilized by technological, scientific, and philosophical activity. Between 1870 and 1910, conventions of space and time scintillated with a critical opalescence.
One can see that Galison is not afraid to engage flights of fancy, and also that he is unusually fond of the word “opalescent”, which I saw more times in this book than in the preceding 30-odd years of my life. Niggling about style aside, the passage does give a feel for the many lenses needed to capture the drama. In Europe, intellectual titans like Poincaré were involved in the struggle to map the world and unify time, while in America, time became the province of businessmen and rail magnates, eventually resulting in the creation of the time zone system we find familiar (albeit not without digressing into some curious permutations along the way).
If you’re wondering how time itself could be so confusing, Poincaré did not. One of the central beliefs of his life was that systems, like time, were just conventions, only to be used until another, more convenient tool came along. If he had been able to follow this belief to its logical end, perhaps it would be he who was remembered as the discoverer of Special Relativity. Certainly his modifications of the Lorentz transformations were essential. Yet he ultimately became too attached to the familiar ether, insisting that there was one “true” time, while Einstein managed to punch through that barrier and recognize that time itself was variable. Galison seems to like Poincaré just a bit too much to judge this failure harshly, but that’s a forgivable flaw in a work that shines a much-needed light on a somewhat-forgotten genius.