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Synchrony and Simultaneity

Hasok Chang

Einstein's Clocks, Poincaré's Maps: Empires of Time. Peter Galison. 389 pp. W. W. Norton and Company, 2003. $23.95.

Time is one of those few subjects that hold a lasting fascination for specialists and nonspecialists alike. In Einstein's Clocks, Poincaré's Maps, the renowned historian of science Peter Galison provides a unique and enlightening view on the origin of time as we know it in the modern age. Deftly weaving together discussions of physics, technology, philosophy and politics, he constructs an account of the development of space-time physics in tight connection with the invention of the mechanisms of clock synchronization and time-zone division that we take so much for granted in everyday life today.

Galison's main characters are Henri Poincaré and Albert Einstein, surrounded by a large cast that includes everyone from the physicist Hendrik Antoon Lorentz to General Helmuth von Moltke. Poincaré and Einstein are also revealed to be activists in the material world of electrotechnology, not ivory-tower intellectuals wholly immersed in abstractions.

Much has been made of the fact that Einstein was an undistinguished patent officer when he published his astonishing set of papers in 1905, including the first paper on the special theory of relativity. The common image is that of an isolated and neglected young genius who made a living at an uninspiring routine job by day but in his spare time dreamed up the most revolutionary physical theory of all time. Not so, says Galison. Not only did Einstein actually enjoy his patent-office job, but the work there taught him about the technologies of electromagnetic clock-coordination, which was one of the chief preoccupations of the engineering world in the half-century following 1860. And in the streets of Einstein's Bern, as in many other major European cities at that time, there were coordinated clocks all around.

The Tower of the Island of GenevaClick to Enlarge Image

So it would not have been theoretical and philosophical inclinations alone that prompted Einstein to insist that simultaneity at distant locations was meaningless unless it was tied to a concrete physical procedure (specifically, an exchange of light signals). Clock coordination was a serious technological problem in the emerging modern world, and Galison documents how it seems that many of the attempted solutions literally passed through Einstein's hands as he processed the patent applications. Special relativity was born of a combination of this down-to-earth (or, down-to-the-wire) inspiration with Einstein's abstract thoughts concerning theoretical electrodynamics and the positivistic philosophy garnered from Ernst Mach and others. Galison's examination of these material-technological roots of relativity is a significant contribution to the historiography of modern physics. In trying to understand Einstein's motivations in crafting the special theory of relativity, historians and philosophers of science have traditionally focused on his positivistic critique of absolute space and time as empirically meaningless, or his fondness for general axioms such as the principle of relativity. Without denying the relevance of Einstein's philosophical and theoretical concerns, Galison stresses how those concerns arose in connection with the concrete realities of Einstein's quotidian world. The technological strand of the relativity story complements the other strands, and at the same time provides a better understanding of how all the strands came to be intertwined.

Galison's discussion of Poincaré is even more extensive and persuasive. Whereas Einstein's involvement with the world of time coordination tended to be local and hands-on, Poincaré's was global and overtly political. (The contrast between the two is summarized insightfully in the final chapter.) As a leading member of the French Bureau of Longitudes, Poincaré became a key figure directing the effort to synchronize clocks by telegraphic signals throughout the French colonial dominions, which was also an essential part of the mapmaking process, because accurate times were necessary for accurate measurements of longitude. In such efforts at standardization and precision, Poincaré and his collaborators were not only attempting to bring modernist rationality to the very fabric of space and time but were also battling the global dominance of the British Empire as it established Greenwich as the site of the prime meridian and foiled the French proposal to decimalize time.

Poincaré traveled freely between the worlds of technology, philosophy and physics, eyes always fixed on the goal of progressive rational order. Most striking is Galison's observation that Poincaré applied the telegrapher's standard convention of time-coordination by exchange of signals in reaching an ingenious and insightful reinterpretation of Lorentz's concept of "local time." A fresh and richer understanding of Poincaré's philosophy of conventionalism emerges; the abstruse passages from his philosophical tracts ring truer as Galison recites them, resounding with the weight of the concrete world. The last section of chapter 4, which summarizes Galison's account of Poincaré, is a tour de force.

After the French RevolutionClick to Enlarge Image

After all is said, the overall picture painted is quite like the one promised early on in the book: "Once in a great while a scientific-technological shift occurs that cannot be understood in the cleanly separated domains of technology, science, or philosophy." The turn-of-the-century revolution regarding time cannot be understood as something simply caused by material conditions or by abstract thought; rather, it resembles "the volatile phase changes of critical opalescence." How often such thoroughgoing changes have happened (or can or should happen) will be an interesting question for the historians and philosophers of science to ponder. What is certain is that we very rarely see Galison's sort of multilayered historical account of the momentous changes that do occur. There are only two other books that come to my mind as comparisons (both found in Galison's extensive bibliography), which the readers of this book may also appreciate. David S. Landes's Revolution in Time (Harvard University Press, 1983) treats "clocks and the making of the modern world" in earlier historical periods, with a good emphasis on economic history as well as horology and philosophy. Crosbie Smith and M. Norton Wise's Energy and Empire (Cambridge University Press, 1989) places the scientific work of William Thomson (Lord Kelvin) in the contexts of Victorian-era politics, industry and religion. When it comes to modern physics, I would venture that Galison is the only person who could have written a book quite like this.

Those who know his previous works will not be surprised by this new arrival. Here Galison continues brilliantly with his project of understanding the "material cultures" of modern physics, as seen in his inimitable Image and Logic (University of Chicago Press, 1997). Also unmistakably present is his signature blend of history and philosophy, combined with lucid and accurate explanations of difficult concepts and practical procedures of modern physics—to be expected, one might say, from a man who has been a professor of not only the history of science, but of philosophy and of physics at Stanford and Harvard. Galison is also known for his ability to connect seemingly esoteric scientific developments with both large- and small-scale currents of politics, and that aspect of his scholarship is exhibited as clearly here as ever. Also evident are his sharp eye for the telling detail, his evocative vignettes and turns of phrase, and his mastery of a formidable range of sources.

Einstein's Clocks, Poincaré's Maps is a treat. Though a short book by the author's own reckoning, it is packed with an abundance of challenging philosophical thoughts and delightful historical connections, which are worth pondering at length. Scientists, historians and philosophers of science, and many nonspecialists will all find this book enlightening and enjoyable. Over-busy or hesitant readers can get a good sense of the content and approach of the book by reading the first chapter, or even just that chapter's last section. But once that far in, I suspect they will want to go on.

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