Einstein's Clocks and Poincare's Maps

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Einstein's Clocks and Poincare's Maps Page 9

by Peter Galison


  This was a remarkable moment. M, the most precisely forged and measured object in history, the most individually specified humanmade thing, had become, by its burial, the most universal. Here was an object manifestly in France and yet not in France, religiously redolent and yet stridently rational, absolutely material and yet completely abstract. In an age when “family, country, church” had become “family, country, science,” K and M were perfect emblems of the Third Republic: buried in specificity, risen in universality. The symbolic resonance of the meter was lost on no one. Back in 1876, the Republic had even memorialized the new meter by striking a richly iconographic medal in honor of the standard, the scientists who were constructing it, and the glory of the original meter chosen during Germinal of Year III.5 On the occasion of the sanctioning in 1889, French newspapers recalled with “patriotic satisfaction” how shortly after the “disaster of 1870” foreign scientists, even those who had previously impugned French precision, now acknowledged its triumph.6

  Before the ink was dry on the Convention of the Meter, delegates were planning new standards that would be built on the model of M. Scientific-technical conventions not only garnered symbolic capital for the country or countries that spearheaded them, but they also engendered real benefits for trade exports and smoothed zones of national confrontation. Conventions were also responses to the sudden confrontation of industrial products at the international expositions, the commercial “chaos” to which Dumas had referred. But conventions also mediated the crossing of train lines and schedules, and blame rapidly fell on their absence when trains smashed into one another. For much of the early nineteenth century, regional (even national) systems of communication, production, and exchange had been free to grow in relative isolation. In the last third of the nineteenth century, systems collided at myriad boundaries in the colonies, markets, and fairs. It was this friction that the conventions were designed to ease. They were patches at the ragged fronts at which telegraphic, electric, and railroad networks met.

  Figure 3.2 Burial of the Meter. In the ceremonial 1889 “sanctioning” of the standard meter and kilogram at Breteuil (near Paris) the most painstakingly created physical objects were buried, so they could function externally as universal measures. Here M lies in its protective metal case on the upper shelf of its triply locked underground vault, while K presides over its six “witnesses,” three standing to each side. SOURCE: LE BUREAU INTERNATIONAL DES POIDS ET MESURES: 1875–1975, P. 39.

  Governments drew up conventions to calm the frantic rustling of incompatible maps as navigators tried to plot routes at the boundary of colonial dominions. They introduced conventions to facilitate the movement of dynamos, gear trains, and steam engines. Regulating these confrontations required hard-fought instruments of accommodation, and their number multiplied: conventions of war; conventions of peace; conventions of electrical power; conventions of temperature, length, and weight. Conventions, as we will see, of time.

  The years after Poincaré’s January 1887 elevation into the Academy of Sciences came at the height of debate over these new standards. Academicians took an interest down to the detailed metallurgy of the meter bars, and their fascination with the meter led to further conventions, as when one of France’s eminent astronomers submitted a paper to the Academy in which the meter served as a model for the decimalization of money. When, just after the sanctioning of the meter, one challenger wrote the Academy to dispute the fidelity of the new bars to the old Archives standard, Berlin astronomer Förster laid down the law: “The international committee of weights and measures [finds it] unacceptable to allow the base of the metric system to depend on uncertain and incessant corrections, now that that base has been materially defined by the international prototype.”7 M now ruled alone.

  Pushed by the French at every turn (in part out of principle, in part as a countermeasure to the force of imperial Britain), the concept of convention widened, condensing into a single word a triple resonance. Convention invoked the revolutionary Convention of Year II that introduced the decimal system of space and time; convention designated the international treaty, the diplomatic instrument that the French, more than any other country, pushed to the fore in the second half of the nineteenth century. More generally, convention is a quantity or relation fixed by broad agreement. A convention, fixed by convention, in the tradition of the Convention. When gloved hands lowered the polished standard meter M into the vaults of Paris, the French, literally, held the keys to a universal system of weights and measures. Diplomacy and science, nationalism and internationalism, specificity and universality converged in the secular sanctity of that vault.

  But if France could lock space and mass in the protected lower basement of Breteuil, time proved more elusive. At the beginning of the 1880s, one French review lamented that clocks were extraordinarily recalcitrant, each one’s own “personality” repelling any attempt to regularize it by making corrections based on temperature. Not that French astronomers and physicists had not tried. All over Europe, neighborhoods, cities, regions, and countries were struggling to standardize and unify their clocks. In Paris and Vienna during the late 1870s, industrial steam plants injected subterranean pipes with compressed air, then modulated that pressure to set clocks pneumatically around the city. Customers could wander through pneumatic shops to select their preferred display of Victorian exactitude.

  At first the fifteen-second delay caused by the time it took the pressure pulse to race under the streets of Paris seemed like nothing. Yet time sensitivity had sufficiently mounted by 1881 that even this tiny delay (causing the clocks at different points in the pipework to differ from one another and from the Observatory) became visible. Astronomers caught the problem, so did the engineers of bridges and roads. Soon the public did as well. At first the engineers tried to shrug off the discrepancy: “this small discordance, indisputable in theory, has little practical importance since we are only dealing with clocks that display minutes, and where the minute hands jump in steps and do not permit further divisions, even approximately between that division of time.” The clock minders hastened to add that they would offset the Observatory’s clock by the fifteen seconds the pulse took to reach the outermost reaches of the network. To be exact, they then mounted retarding counterweights on each pneumatic clock based on its distance from the center. In this way, they reassured their readers, “practically the whole of the discrepancy will be corrected.”8

  Figure 3.3 Pneumatic Unification of Time: The Control Room (circa 1880). From the control room at the Rue du Télégraphe in Paris, the pipelines pumped time under the city streets to synchronize clocks in every quarter of the metropolis. SOURCE: COMPAGNIE GÉNÉRALE DES HORLOGES PNEUMATIQUES, ARCHIVES DE LA VILLE DE PARIS, VONC 20.

  Figure 3.4 Pneumatic Unification of Time: The Display Room (circa 1880). Here customers—both commercial and private—could purchase clocks that would register the carefully timed bursts of air that they would receive through the pneumatic pipes of Paris. SOURCE: COMPAGNIE GÉNÉRALE DES HORLOGES PNEUMATIQUES, ARCHIVES DE LA VILLE DE PARIS, VONC 20.

  Two striking features of time coordination emerge from this little vignette. First, time awareness had become acute. Before the nineteenth century, clocks normally did not even have minute hands.9 Now a fifteen-second discrepancy could drive engineers to modify public clocks. Second, the transmission time—even of a pressure wave traveling at the speed of sound—looked to professionals and the public like a problem demanding correction. But if the late-nineteenth-century public wanted their seconds adjusted, astronomers had long grown used to far greater precision. Urbain Le Verrier, director of the Paris Observatory and co-discoverer of the planet Neptune, had long since wanted electrical time unification. Synchronizing clocks by pneumatic means would have been absurdly inaccurate in the context of late-nineteenth-century astronomical work. In 1875, no doubt prompted by the Observatory’s role in the unification of the system of weights and lengths, Le Verrier proposed standardizing and unifying Pa
risian time by electricity, as the astronomers had already unified the various rooms of their own observatory. Physicists Cornu and Fizeau, along with the Observatory’s astronomers, all endorsed the idea. It was a perfect Polytechnique project. Le Verrier lost no time in pressing the Department of the Seine for support. Le Verrier and his astronomers insisted that their goal was to extend the interior order of the observatory to the whole of the city: “I propose to the City of Paris to give the public clocks a synchronized action and a precision superior to that which we have habitually satisfied ourselves. . . . If the City of Paris agrees . . . it will find here the opportunity to give a new and fertile boost to the art of clockmaking which has made famous the names of French artisans.”10

  Paris agreed, promptly establishing an illustrious commission to guide its clocks. Gustave Tresca would join the time standardization drive; it was he who was supervising the production of the standard meter sticks and weights that would grace the basement at Breteuil. Edmond Becquerel would be there, too, as a major French physicist (he was the father of Henri Becquerel of radioactivity fame). Renowned architect Eugène Viollet-le-Duc served on the commission, no doubt because of his famed restorations (coordinating grand church clocks presented huge architectural and structural issues). Charles Wolf, astronomer at the Paris Observatory, was a commissioner; he had invented much of the observatory’s electric time-coordination system. The astronomers and their allies ran a clock-building competition and soon had a working trial system.

  By the time the commission reported back to the City in January 1879, Le Verrier had died. But his plan lived. A dozen synchronized clocks would dot Paris, joined by telegraphic cable to the mother clock in the Observatory. Built precisely on the model of coordinated precision they had erected in their own Observatory, each of these secondary clocks had its mechanism set to run fifteen seconds fast each twenty-four hours. A controlling pulse from the Observatory drove an electromagnet in each public clock and that magnet slowed the pendulum, pulling the remote clock into synchrony with the mother clock. Each secondary clock radiated time electrically, resetting other public clocks in city halls, important squares, and churches. From now on, the report proclaimed, the public would have forty public clocks announcing the time correct to the nearest minute—indeed, to the nearest second just after it received the reset signal. Still, there were spatial and legal limits past which the Observatory time wires would not go:

  We have not included in the list of clocks to be regulated any belonging to the railroad. It is not that we have misunderstood the enormous interest that the public would have in knowing that these clocks are in agreement among themselves and with those of the City. But . . . it seemed to the Commission that it would be imprudent to engage the City . . . itself in such a complex service, where big interests are in play, and where its responsibility in case of accident arising from the regulation of the clocks could be engaged in an unfortunate way. One can not doubt, however, that the [railroad] Companies, when they see at their doorstep all the clocks of the City regularly indicating the time, and all the same time, will spontaneously put themselves in accord with the time of the Observatory. That day, the unification of time in Paris will be the unification of time in all of France.11

  Here was an admirable vision: the Observatory would stretch its walls until Le Verrier’s system embraced the entirety of Paris. A clock at the country’s center of precision would multiply itself until every jeweler, every citizen, would have astronomer’s time within a stone’s throw. By example, trains and finally all France would follow. Through this series of symbolic reflections—a temporal hall of mirrors—Le Verrier’s astronomically set pendulum would set the time of every clock in the country.

  The clocks never worked. Ice in the sewer systems promptly cut the wires at numerous points: the current ended up driving the clocks without the intervention of the mother clock. Soon public clocks all over Paris were hawking their own peculiar times. In embarrassment and anger, the commission attacked the chief engineer, precipitating a cascade of mutual recriminations over patents and the patent failure of the public clocks to register anything like the right time. Pleading that the commissioners use his latest inventions, the chief engineer lambasted clocks that were accurate only on receiving their reset signal: “In regarding the clockface at any moment, the observer must have the absolute certainty that the clock is correct to within a few seconds at the most, not to within five minutes.”12

  During 1882 and 1883, reports streamed back to the authorities that the clocks of one arrondissement after another were not getting proper electrical guidance from the Observatory. By the spring of 1883 not a single public clock tied to the secondary regulators was receiving any current at all.13 French authors conceded that their country had failed to dominate the time unification of cities. Adding insult to injury, it was London, home of the twelve-inch foot, that led the way toward standardizing time.14

  After establishing the glorious, rational meter, it was galling to the French scientific establishment that synchronized time had slipped out of their hands. In 1889, the Observatory director pleaded with city authorities that this temporal chaos had to stop: “The Counsel of the Observatory, has been disturbed many times by the manner in which the distribution of time has functioned in Paris. The results obtained up till now are in effect far from being satisfactory, so much so that given the numerous protests, the director of the Observatory had in effect to request the erasure of any mention of ‘observatory time’.”15 At the 1900 Universal Exposition, foreigners would see this sorry state of affairs. Couldn’t the municipality and the Observatory build a system “more worthy of a city like Paris”? Under these circumstances, it became ever clearer that railroads were far from likely to mimic “spontaneously” the Observatory-City system, as Le Verrier had dreamed.

  Times, Trains, and Telegraphs

  It was not that the French railroaders did not want coordinated time. They, like the rest of Paris, were transfixed by the coming triumph of the Parisian standard meter as its 1889 sanctification drew near. The industrial General Review of Railroads opened its 1888 discussion of time by referring directly to the extraordinary success of metrical reform:

  The metric system, one of the most glorious creations of French genius, has already conquered half of the world, and its complete triumph is no longer doubted by anyone. Its authors have added a new calendar, but they have not concerned themselves with fixing the beginning or middle of the day . . . questions which seem resolved by the advance of the sun. It required the rapidity of communication by rail and telegraph to seed the idea of choosing, more or less arbitrarily, the time of one locality to be imposed on others, and to create in this way normal or national hours. This has given birth to a confusion of a new kind but of the same type as that due to the multiplicity of ancient national weights and measures.16

  In France, as in many other countries, each train system used the time of the main city served. Bit by bit, as lines from Paris wound deeper into the hinterland, they had chased away local times until, by 1888, Paris fixed the whole country’s railroad time. Clock faces in the courtyards and departure lounges indicated the exact mean time of Paris, while platform clocks ran behind the outside clocks by three or sometimes five minutes to give the traveling public a margin of error. So as passengers waited in train stations outside of Paris—in Brest or Nice, for example—they experienced three times: their city’s own local time, Paris time (in the waiting room), and an offset time in the track area. (Train time ran in advance of Brest by twenty-seven minutes and behind Nice by twenty.) The Revue analyzed other countries’ time schemes, examining each one’s solution to the time problem. Russia had unified time in January 1888. Sweden had set its clocks one hour later than Greenwich. Germany staggered under multiple Land-based times.

  “Nowhere else has the question of time been posed in a more pressing manner than in the vast network of railroads of the United States and in the English possessions of North Amer
ica.” Grounded in the North American railroads’ April 1883 decision to synchronize all their clocks by zones, the Americans and Canadians had chosen Greenwich as time zero, blocking out huge longitudinal swaths from “Intercolonial time” in the East to “Pacific time” in the West. “Let us add, before leaving America,” the French railway journal concluded, “that the [American] charts and color maps offered to the public seem to us, by their clarity and beauty of their printing, noticeably superior to that which we usually see in our countries of ancient civilization.” According to the Revue, when international scientific delegates gathered in Washington, D.C., in October 1884, it was the railroaders who had been able to remind them that “any change would be useless and inopportune.” Now the stakes were clear: could the French—could the world—adopt a “generalized American system”? For the French railroad Revue, this was a question that should not be left exclusively in the hands of geographers, geodesists, and astronomers.17 No doubt with Paris standoffish astronomers in mind, the author wrote: “It is only when the railroads and telegraphs have realized [time] reform that one can hope to see their example followed by other administrations and municipalities. And it is only then, as in North America, that the reform could be complete and could make felt its benefits.”18

 

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