Einstein's Clocks and Poincare's Maps

by Peter Galison

  French railroaders, telegraphers, and astronomers looked with a mixture of admiration and anxiety at Britain and the United States when it came to time reform. America stood out for its industrial distribution of time, Britain for its world-dominating network of undersea cables. When Henri Poincaré joined the Bureau of Longitude in 1893, he entered a world quite different from the vast commercial and scientific enterprise administered by the British and the Americans. Clocks ran with stunning precision in the Observatory and appalling inaccuracy in the streets of Paris. The French, especially the Polytechnicians, rued this urban failure, but they were proud of their principled, mathematical, philosophical approach to standardization. They had brought the Enlightenment meter to a triumphant victory and begun extending the universal rationality it announced into the chaotic dominion of time.

  On the other side of the Atlantic, North American time reform could boast no leader with the scientific stature of Le Verrier. It simply is not possible to reduce the American time coordination story to the work of an individual, an industry, or a scientist, despite many attempts. Instead, the movement toward synchronization was always critically opalescent, with dozens of town councils, railroad supervisors, telegraphers, scientific-technical societies, diplomats, scientists, and observatories all vying to coordinate clocks in different ways. That effort was so hybrid, so fluctuating in its allegiances and coordinated grids, that astronomers sold time like businessmen and railroaders spoke to the universal order of nature.

  French savants found America’s most impressive science not mathematical physics, mathematics, or pure astronomy, but rather the work of the ambitious Coast and Geodetic Survey. Teams of cartographers and surveyors were busy laying out the boundaries, rivers, mountains, and natural resources of the rapidly expanding country. Like all their fellow map makers, the Americans struggled with time, because time was inseparable from longitude.

  Finding local time on the spot was a matter of watching the sky, then setting a clock by the moment when the sun passed its highest point. Or, more precisely, it meant determining the moment a certain star crossed an imaginary line running vertically up from the northern horizon. If the surveyors also knew what time it was back at a fixed reference point—Washington, D.C., for example—they could then simply reckon the time difference between local and Washington time. If the two times were the same, the surveyors were somewhere on the same longitude line as the Capitol. If the surveyors found their time to be three hours earlier than Washington, then they were an eighth of the way around the globe, to the west.

  The map maker’s problem was therefore always this same question of distant simultaneity: What time is it right now back in Washington or Paris or Greenwich? So explorers, surveyors, and navigators carried clocks (chronometers) set to the time of their port of departure. All the longitude finder had to do was to compare local time to the chronometer. But getting a precision clock to guard proper time in the unsteady motion of a ship’s cabin or on a mule’s back was never easy. Add the vagaries of temperature, moisture, and mechanical failings, and the provision of a stable, precise chronometer became one of the most difficult machine problems ever attacked. For John Harrison, the extraordinary eighteenth-century clockmaker, efforts to build an accurate seagoing longitude clock consumed the whole of his life.19 Gifted though he was, Harrison did not end the search for movable time. The hunt for reliable, transportable clocks continued throughout the nineteenth and twentieth centuries. Astronomers fought long and hard to devise a precise way to use the moon’s movement against the fixed stars as a giant clock readable from anywhere. But the moon’s position was hard to fix mathematically, and in the field or on a ship it was difficult to measure just where the moon was, except for those rare moments when it actually passed in front of a star or planet.

  The single measurement American surveyors most wanted was the longitude difference between the New World and the Old. But the map makers simply could not come to a consensus. One desperate series of attempts—only one among many—began in August 1849, with seven transatlantic voyages in each direction, each bearing twelve accurate chronometers. The hope was that their time cargo would finally show the true difference in time, and therefore longitude, across the Atlantic. In 1851 they stashed on board thirty-seven chronometers, taking advantage of five sailings from Liverpool and two from Cambridge, Massachusetts. After hauling ninety-three chronometers across the seas, the astronomers optimistically claimed a shore-to-shore time difference to within one-twentieth of a second.20

  Such vaunted precision soon rang hollow. Despite the presence of ever-more-vigilant clock tenders on the ships to protect the ticking freight, the measured time difference from the United States to England was, impossibly, different from that from England to the United States. Something on the high seas was confounding the clocks. Astronomers suspected that temperature was probably the culprit, with the lower temperatures far offshore slowing the clockworks. This meant that if a lethargic clock set sail at 1:00 P.M. from Cambridge, Massachusetts, it would arrive in Europe showing that Cambridge time was earlier than it really was and induce British map makers, relying on the clocks arriving in England, to put Cambridge, Massachusetts, to the west of its actual location. Conversely, a slow-running seagoing clock set initially in Liverpool would suggest to the Americans that Liverpool time was earlier than it was, so the New World map makers would draw their maps with Liverpool to the west and therefore closer to the shores of North America. Testing, calculating, and interpolating did little to help. Crowding the ship with more supervisors, better temperature compensators, and superior clocks just spewed out additional conflicting data. Unable to measure the number that mattered most, the longitude difference between North America and Europe, map makers despaired.

  For hundreds of years, cartographers could only dream of being able to send a signal of simultaneity to fix longitude. The telegraph cracked the problem. Over vast distances, an electric current would race a signal through the wires so fast that the reception and transmission seemed practically instantaneous. During the summer of 1848, observatory astronomers from the Harvard Observatory and the Coast Survey tested this new function for the telegraph. One person would tap on the key and the other would listen for a beat at the distant end. Each distant tap would leave a mark on a paper that wound through the receiver’s printing device. One evening, one of the mappers, Sears Walker, wondered aloud if they couldn’t directly observe and transmit their observation of a star passing through the north. Bond replied: Why not make the escapement of a clock act like a telegraph key so the ticks would be heard anywhere and everywhere along the telegraph line? Then, Why not let that clock-driven signal mark on a smoothly turning cylinder located far from the clock?21 By comparing the position of marks made by a locally set clock with the position of marks made by signals sent at known times from a distant clock, surveyors could accurately compare distant and local time.

  distant 12:00:00→| distant 12:00:01→ | distant 12:00:02→| local 12:00:00→|

  For instance, here the local noon occurs about a half-second after the distant noon. Instead of trying to register time by stopping a clock when a star crossed a spider-thread reticle in their telescope, the astronomers could simply measure the distance between lines on their paper. From that simple measurement, the surveyors had longitude.

  By the end of 1851, telegraph cables stretched from Cambridge, Massachusetts, to Bangor, Maine; from there the time signal jumped, in a second transmission, from Bangor all the way to Halifax, Nova Scotia. As American scientists began advertizing their electric time transmitters, they found a ready audience in Europe. Bond noted: “It is a gratifying circumstance that this invention is known and spoken of in England only as the ‘American method,’ and the Astronomer Royal has laid the wires at Greenwich preparatory to introducing it there.”22

  It was not just the astronomers and map makers who cared about the rapid dispersal of simultaneity. Trains had schedules to maintain, and by 1848�
�49 railroads began forming voluntary associations to fix, by convention, the time on which they ran. For much of New England that meant that all trains on or after 5 November 1849 were to adopt the “true time at Boston as given by William Bond & Son, No. 26 Congress Street.”23 Any railroad not already in this common time system soon was motivated to be so. On 12 August 1853, two trains of the Providence and Worcester line slammed into each other at a blind curve. Fourteen people died, and newspapers blamed the tragedy on a conductor with an itchy finger on the throttle and a slow watch at his side. With another bad-watch disaster just a few days earlier, train lines found themselves under immense pressure to coordinate their clocks. Telegraphically transmitted time became a standard railroad technology.24

  Figure 3.5 The American Method. By recording the arrival of telegraph signals on a precisely rotating drum, the transmission of time could be made vastly more accurate than by earlier, acoustic means. For longer stretches (under the Atlantic, for example) the simultaneity men used the more-sensitive method invented by Lord Kelvin: the incoming electric time signal caused a mirror-mounted magnet to twist ever so slightly, which caused a reflected light beam to shift on a sheet of paper. SOURCE: GREEN, REPORT ON TELEGRAPHIC DETERMINATION (1877), OPPOSITE P. 23.

  Figure 3.6 Traces of Time. Telegraph keys and the traces of distantly sent time signals recorded by the “American Method” (1883). SOURCE: CH. HENRY DAVIS ET AL., TELEGRAPHIC LONGITUDE IN MEXICO AND CENTRAL AMERICA (1885), PLATE 1.

  Partly pushing the observatories, partly pushed by them, train supervisors, telegraph operators, and watchmakers accelerated the electrical coordination of clocks both in England and in the United States. By 1852, directed by the Astronomer Royal, British clocks were sending electrical signals over telegraph lines both to public clocks and to railways.25 Soon the Americans were, too. Summing up the status of their time effort, the director of the Harvard College Observatory boasted in late 1853 that the “beats of our clock can, in effect, be instantly made audible at any telegraph station within several hundred miles of this Observatory.”26 During the 1860s and 1870s, coordinated time reached deeper into the cities and train system. Hailed in the press, visible in the streets, studied in observatories and laboratories, the synchronized clock was anything but rarified science. Its capillary extension into train stations, neighborhoods, and churches meant that synchronized time intervened in peoples’ lives the way electric power, sewage, or gas did: as a circulating fluid of modern urban life. Unlike other public services, time synchronization depended directly on scientists. By the end of the 1870s, the Harvard College Observatory was but one site sending time, though for a few years its service was one of the largest. Idiosyncratic developments in Pittsburgh, Cincinnati, Greenwich, Paris, or Berlin set each apart.27

  Marketing Time

  Shortly after those first experiments on electrical time, Harvard Observatory hired a telegraph line to distribute to Boston the time its astronomers had determined by the measurement of the stars. By 1871, the observatory director was charging for the service, hoping to install a prominent clock “so that the public can see and learn to appreciate the method of communicating time.”28 Returns were good: in 1875, the service netted $2,400, a yield sufficiently large that the observatory hired a proprietor for its time business.29 In 1877, Harvard’s Observatory director assigned graduate student Leonard Waldo to manage the time service. By then the Cantabrigians had invested over $8,000 in instruments, clocks, and telegraph lines. Now they needed customers. Using their telegraph to trigger its noon start, Waldo planned to drop a large copper time ball down a mast on top of one of Boston’s higher buildings. He hoped that this public display, visible both to landlubbers and navigators, would dramatically boost the observatory’s recognition. So would a major recruitment of railways. Jewelers and clockmakers too were needed as time clients, not to speak of private individuals who clamored (or ought to, according to Waldo) for precision time. Waldo hoped a widening clientele would persuade big manufacturers that time really was money, or at least was worth buying. Wires multiplied, snaking through the observatory that aspired to be the master clock for all New England.30

  Hard-driven Waldo pounded out his message wherever he could. Encouraged by Western Union, he printed a pamphlet that advertized the time service to a hundred New England cities and towns. His time, Harvard Observatory’s time, would be based on an impressive Frodsham clock, corrected once each day at 10:00 A.M. to within a fraction of a second. From this master clock, time would course through the region on two circuits in addition to the main one linking the observatory, the Boston Fire Department, and the city of Boston. In the unlikely event that the Observatory clock failed, Waldo promised his time-hungry customers that they would receive a back-up signal from clockmakers William Bond & Sons. All day long, at two-second intervals, pulses shot out from the Observatory, skipping, for identification purposes, every minute’s fifty-eighth second, while every fifth minute the service would omit the pulses that would normally go out on the thirty-fourth to sixtieth seconds.31

  Citizens like the proprietor of the Rhode Island Card Board Company wanted to know the time:

  Will you have the goodness to inform me whether the time furnished at the W[estern] U[nion] Telegraph office Boston from your observatory is actual Cambridge time, or Boston time.—That is, whether an allowance is made of the difference in time between the two places before transmitting the signals—[.] Does the little hand that beats seconds on the dial in Boston correspond precisely with the beating of the standard clock at Cambridge? Are correct signals furnished to Providence by telegraph direct from your observatory?—A number of Citizens of Providence and vicinity having fine watches are desirous of having this information.32

  Did cardboard manufacturing demand split-second timing? Rather, the cardboard mogul and others like him wanted exact time because their “fine watches” demanded it; they had come to view the exact coordination of their timepieces as a value not captured by the purely pragmatic. Fostering such a modern temporal enthusiasm was Waldo’s great hope. Not only his own circulars, talks, and correspondence but surely also the ever-increasing role of railroads had begun to create a sensibility that could only work to the advantage of Harvard’s time service. Five years of selling time had done much to foster this awareness. Waldo put it this way:

  In . . . time the community generally had been unconsciously educated to the desirability of a uniform standard of time. Accurate time-pieces, in many places, were daily compared with the Observatory signals, and their rates so determined were considered authoritative. So critical, indeed, had the subscribers become, that errors of a fraction of a second were detected and commented upon.

  Did the running of trains and the calibration of fire bells require an accuracy that would better an error of four-tenths with one of two-tenths of a second? Of course not. Yet Waldo both pushed the public and was pushed by them to ever greater precision. In his own way, he participated in the creation of a modernist time sensibility, one with bounds that far exceeded the practicalities of precision.33

  Back at his time factory, Waldo struggled to protect his regulator clocks from variation in climate, to systematize telegraphic connections, and to engage a dedicated observer to determine clock error each day. To guard the university clocks from variations of temperature, the astronomers sealed a basement room against the elements. This “clock room” stood in the west wing of the observatory and was completed 2 March 1877. Some 10' x 4'2" wide, 9'10" high, its double walls protected the all-important clocks. Only a safe door penetrated these thick barriers. When the door closed snugly it sealed against felt packing. Inside, each of the three treasured clocks stood on marble slabs on brick piers, their faces illuminated by tin reflectors so they could be viewed from behind small, thick glass windows (immediate human presence posed a threat to accuracy). In observatories around the world, from Berlin to Liverpool, from Moscow to Paris, similarly obsessed astronomers shaved errors from their mother
clocks.34

  Split-second timing was one thing; marketing it was another. At the limit of the Boston time-selling region stood Hartford, a city that had vacillated between its own local time and that of New York City. When a Hartford worthy, Charles Teske, wrote to Waldo in July 1878, indicating his interest in converting his town to Harvard Observatory time, Waldo took notice. Teske reported that he had corralled the Hartford Fire Department and its committee, fire departments typically being the agency whose noon bell signaled time to the public. Hartford’s mayor liked the idea of purchasing Cambridge time to set hammer against bell at noon and midnight. But rounding up diverse interests and divergent times was less simple, as Teske lamented to Waldo: “It is like awakening the dead out of their sleep, to get people interested in this matter, for we have here in Hartford all sorts of time and everybody claims that his time is correct.” Teske reckoned it would cost him a good deal of effort, and a reasonable price from the observatory, to nail down the board of aldermen and the common council. But more than just money, autonomy was at stake. “Will you give us Cambridge time? Can you give us Hartford Time? What is the exact difference between Cambridge & Hartford?” Several months later he was still hammering away at his various opponents.35