by Ken Alder
These questions all came to the fore at the first international geodetic conference, held that very year in Berlin. The geodesers in attendance knew better than anyone the shortcomings of the original determination of the meter. Since Delambre had published the final volume of the Base in 1810, his scientific successors had further refined their knowledge of the earth’s shape. Each passing decade had widened the gap between the Archive Meter and the known size of the earth.
During the past half-century, moreover, each European nation had triangulated its own territory, mapping its terrain with reference to the regular ellipsoid that best represented the earth’s curvature through its own particular lands. It was as if each European nation inhabited its own eccentric planet. Some of these nations, Prussia first and foremost, were now eager to fit their maps snugly together with those of their immediate neighbors. For this they needed a common standard and uniform procedures. The Germans suggested a technique for doing this: Gauss’ method of least squares, by which the triangles of every nation could be brought into optimal alignment. In 1861 General Johann Jakob Baeyer of the Prussian army, longtime director of its cartography department, had secured permission to establish a Central European Geodetic Association in Berlin. As he noted, “By its very nature, such an enterprise cannot be the work of a single state; but what one [nation] cannot realize alone, many may achieve together. And if in the process Central Europe should unite for this purpose, devoting all its might and resources, a great and important work will be called into being.”
It was an alarming and exhilarating call, reminiscent of nothing so much as the calls for European unity that had come out of Revolutionary France seven decades earlier. The geodesers were determined to bring their numbers into alignment: to live, as it were, on the same planet. Their association became the nucleus of the world’s first international scientific association.
But when the Germans sent out invitations to expand the association from Central Europe to the entire continent, the French response was divided. Some scientists saw it as a chance to revitalize French geodesy, which was still using the seventy-year-old techniques of Delambre and Méchain. Others saw it as an attempt to subordinate France’s triangles to a pan-European grid and to subvert the one true Archive Meter as determined by Delambre and Méchain, whose results ought only to be revised “with caution and intelligence.” The French government refused to send delegates to the Berlin convention. Relations between the two continental powers were deteriorating rapidly and the French did not want their meter publicly impugned. When one French scientist rashly suggested that the Academy launch its own preemptive expedition to remeasure the earth—and get it right this time—his colleagues quickly shut him up. A standard was fixed, or it was not a standard.
The international geodesers understood this. At the meeting in Berlin, General Baeyer and the rest of Europe’s geodesers agreed that the meter should remain the standard of length—not because it was based on nature, but because it was widely accepted. If the natural origin of the meter was a fiction, it was a useful fiction. “In truth, the meter draws a good deal of its prestige from the notion, flattering to human pride, that our daily measures are drawn from the dimensions of the globe we inhabit.” They insisted, however, that the Archive Meter was defective, and that a new meter bar be made to replace it.
For the previous seventy years, nations adopting the metric system had been obliged to beg France to calibrate their weights and measures for them. This gave France an unseemly custodial power, and the bar itself had been worn down by the continual comparisons. In 1837 a Bavarian scientist found that the ends of the bar were scratched. In 1864 a microscopic inspection revealed that the surface there was pitted. Moreover, chemists had discovered that the platinum, once considered “pure,” was actually adulterated with allied metals (such as iridium), complicating the bar’s rate of expansion with temperature. In sum, there was reason to fear that the bar’s length had altered since 1799, could not be accurately described now, and would change in the future. Nothing, it turned out, was more ephemeral than yesterday’s cutting-edge science. The geodesers of 1867 agreed that the new bar should differ “as little as possible” from the Archive Meter. But they also wanted a permanent international agency to take charge of this new standard so that no one nation could claim the standard for itself.
This sent the French into a paroxysm of self-doubt. Would Germanic precision supplant French precision, as Germany was supplanting France? It was as if the entire nation had taken its cue from Méchain, making his error collective, and his paranoia general. Some French scientists, notably at the Bureau of Longitudes, welcomed the chance to put the metric standard on a secure footing, but the Minister of Commerce rejected any move to replace the meter. And scientists at the Observatory and the Academy concurred. The Archive Meter was in excellent shape, they reported, and remained the only possible standard. Indeed, they went so far as to deny that their Revolutionary forebears had ever claimed that the meter should be based on nature at all, or that all meridians were the same length, or that the length of the Paris meridian might be measured definitively. Thus they thrice denied the founding premises of the metric system. Yet they concluded that they would rather invite their foreign colleagues to Paris than see them establish a rival system.
So seventy years after Napoleon I promoted the first international scientific conference, Emperor Napoleon III, his nephew, sent out invitations for a second metric conference to be held in Paris. This time, scientists from all the world’s nations—including the Americans, the British, and the Germans—were invited. “Today, as in the distant days of the great International Commission of Weights and Measures, it is by inviting French and foreign savants to work together in complete equality that we may best preserve the metric system’s universality and obtain truly international models, perfectly identical with those in the French Archives and capable of serving the scientific needs of each nation, while preparing the world for the general adoption of the metric system.”
In July 1870, two weeks before the conference was to start, Prussia and France went to war. The German delegates stayed home, but scientists from fifteen other nations, including the United States and Britain, held their first assembly in Paris on August 8. At the time, the French army was falling back on Metz. Under the circumstances everyone agreed that any final determinations would have to wait until all their colleagues were present. Then the French brought into the open the question that haunted their scientific nightmares: did their guests really expect to base the new meter on the size of the earth? It took several days for the German-born Swiss delegate Adolph Hirsch (a co-organizer of the Berlin geodesy conference) to reassure his French colleagues that “no serious scientist in our day and age” would contemplate a meter deduced from the size of the earth. The new meter bar would be built to match the old one.
The Prussian army won the war; the French emperor abdicated; the Prussian king became emperor of Germany; and France (after ghastly bloodshed) became a republic again. The French lost Alsace and Lorraine, but they regained democracy. In 1872 the new French Republic reissued invitations for an international metric conference. The German Empire sent several delegates. Wilhelm Foerster, their chief representative, was an affable enthusiast for world metrical harmony. For nearly a month, scientists from thirty European and American nations discussed the form, content, and distribution of the replacement measure. It was all very collegial. They agreed that the new bar should be made as similar to the old one as possible, right down to its impurities: a mix of 90 percent platinum and 10 percent iridium. They also resolved to make as many standard meters as there were nations, and only then to select one to serve as the definitive standard: a first among equals. Finally, they proposed a permanent International Bureau to superintend these activities.
The “Convention of the Meter” of 1875 remains the framework for all international metric standards, including those for electricity, temperature, and other phenomena.
Although the French delegates were not keen on a permanent International Bureau of Weights and Measures, they offered to house the institution in Paris rather than see it wrested away by Berlin. The Pavillon de Breteuil, which they donated for its headquarters, had been almost completely destroyed during the recent Prussian siege of Paris and was rebuilt at international expense.
FORGING THE NEW METER
In the 1870s scientists at the workshop of the Conservatoire National des Arts et Métiers in Paris experimented with the construction of a new standard meter. The new definitive meter was not completed until the late 1880s. (From Illustration [16 May 1874], 316; photograph by Roman Stansberry)
It would take fifteen years of scientific controversy—including a spat over the platinum-iridium alloy that nearly caused another Franco-German rift—to construct new meters to the Bureau’s specifications. By then virtually every European nation had mandated gradual introduction of the metric system. When the bars were shipped out in 1889, the old Archive Meter, built to match the meridian data collected by Delambre and Méchain, lost its universal status and fell, like the Châtelet toise before it, into the pit of history. It became just another stick of precious metal, worth the market price for platinum, plus whatever value human memory ascribed to it. But, needless to say, the French government did not melt it down. They preserved it, as before, in the National Archives, a historical artifact like any other, to be read as evidence of the past.
Delambre and Méchain, the myth now went, had heroically measured the earth so that the meter could be set at one ten-millionth of the quarter meridian. Their error was forgotten, even as the embodiment of their error was preserved. It was preserved in 1889 when the new platinum-iridium bar replaced the old Archive Meter. It was preserved again in 1960 when the International Bureau redefined the meter in terms of the wavelength of light emitted by a specific energy transition in the krypton-86 atom. And it was preserved again in 1983 when the Bureau redefined the meter as the distance traveled by light in a vacuum in 1/299,792,458 seconds (with time, the fundamental unit, now defined by an atomic clock). Thus, the new quantum mechanics, famous for its principle of measurement uncertainty, has again provided the Bureau with a standard based on nature that can be specified with exceeding (but never final) precision. Yet each redefinition, including the most recent, has been concocted so as to preserve the length of Delambre and Méchain’s original meter of 1799.
The truth belongs to everyone and no one. It is public property and ephemeral, or else it is not the kind of truth we call science. But error is forever because, having happened once, it exists, like an unhappy family, in its own particular way. Delambre and Méchain built their lives into the meter: they traveled the meridian, they selected its stations (including their own private sites: the country château at Bruyères, the observatory on the rue de Paradis), they peered through the scopes, and their inky fingers calculated the angles of the earth and the stars. The meter is their epitaph because only a person’s mistakes are truly his own. Yet in accepting their meter, we have made their error our own, which is to say public, singular, and true. Theirs was truly an error for all people, for all time.
By the middle of the twentieth century, the vast majority of the world’s nations—with the major exceptions of the British Commonwealth and the United States—had joined the metric system. Each time, the precipitating event was political upheaval. Shortly after it became a republic in 1912, China announced that it would switch to the metric system during the next decade; the law was enforced after the revolution of 1949. Tsarist Russia recognized the metric system in the late nineteenth century, but it was the Soviet Union that in 1922 made metric measures mandatory. Despite earlier legislation, Japan and Korea did not seriously convert to the metric system until after World War II. The system spread through Asia and Africa in the wake of colonization, and later in the wake of decolonization; either way, metric uniformity appealed to those who wished to legitimate their territorial rule and create a national administration, even as they opened up their territory to extranational market forces. Thus Jawaharlal Nehru took India metric soon after the British left in 1947. And the more the metric system spread, the more irresistible became the logic of joining the world’s preeminent international network.
Britain was the first economic power to adopt the metric system without passing through radical political upheaval first. No doubt this explains why it was also the last. The Victorians had concentrated on unifying their imperial measures, itself a daunting task. By the mid-nineteenth century they had largely eradicated local variations and anthropometric measures, so they had little incentive to switch from their traditional physical standard in London to a different “natural” one in Paris. An antimetric lobby complained of the costs, confusion, and resentment that would accompany conversion. Above all, they scorned the metric reformers as elitists, and presented themselves as practical men—always good politics, especially when they could claim to be anti-French to boot. The scientific eminence John F. W. Herschel dragged Méchain’s secret error into the public eye and charged him with “disingenuous concealment” in the affair of the Barcelona latitudes. If Britain really insisted on a measure based upon nature, Herschel suggested, it should adopt the length of the earth’s axis from pole to pole. As this distance just so happened to equal 500,500,000 inches it would provide a natural basis for the British Imperial inch. Thus, with a little British ingenuity, everything could be brought thoroughly up to date—without changing anything at all. The engineer William Rankine attacked the metric reformers with this ditty.
A party of astronomers went measuring the earth,
And forty million metres they took to be its girth;
Five hundred million inches, though, go through from pole to pole;
So let’s stick to inches, feet and yards, and the good old three-foot rule.
Not until 1965, on the eve of its decision to join the European Common Market, did the British government announce a ten-year transition to the metric system. More than thirty years have elapsed, and the “harmonizing” process drags on—as do the protests. On January 1, 2000, a new era dawned in Britain: shopkeepers were obliged to sell in metric units. A few months later, Steve Thoburn, a Sunderland grocer who sold bananas by the pound, had his scales confiscated. The tabloids worked themselves into a frenzy of indignation. This is the sort of local resistance that has everywhere accompanied the introduction of the meter. The British conversion may involve a simple translation from one set of impersonal measures to another; yet even this degree of disorientation can feel like a loss of sovereignty. And in a sense, Britain’s long-delayed adoption of the metric system was precipitated by a loss of sovereignty: the decline of the Commonwealth, and Britain’s entry into the European Community.
Once Britain committed itself to conversion, the rest of the Commonwealth countries followed suit. In 1970 Canada announced that it would not wait upon its huge trading partner to the south. A voluntary transformation was envisaged, coaxed along by an educational campaign, with animated films such as Ten: The Magic Number. As consumer goods in metric units proliferated (toothpaste first), some Canadians protested. But generally Canadians have been puzzled by their own “sheepish” willingness to accept the meter—to the point where they have come to consider it a point of national pride that their country has gone metric while America has not.
Americans have been arguing about the metric system since shortly after the signing of the U.S. Constitution. Article 1, section 8 granted Congress authority “to fix the Standard of Weights and Measures.” Who would have thought so quantitative and banal a subject would elicit such passion? Industrialists and scientists, mystics and nativists, curmudgeons and enthusiasts, schoolteachers and politicians have all battled over the world’s measure. To date, America’s metric advocates have always failed.
Paradoxically, it is America’s modernity—its freedom from “feudal” institutions, its origin in colonial rule, and hence the relative un
iformity of its measures—that explains the country’s failure to switch to the ultramodern metric system. As a large and homogeneous economy, the United States already enjoys most of the coordination advantages that come from common standards, reducing its incentive to join the rest of the metric world. And even though doing so would undoubtedly bring long-term economic gains, the American government is notoriously beholden to business groups and populists, who insist on short-term payback. America is the only country in the world that still thinks it can afford to stay outside the metric system even as it participates in the world economy.
Not until the 1830s did the United States even define a national standard. A Swiss geodeser named Ferdinand Rudolph Hassler, who had arrived in the United States in 1805 bearing one of the definitive iron meters of the International Commission, became the first director of the National Bureau of Standards. He affirmed the decision to stick with the English weights and measures. In 1863, within a month of its founding, the National Academy of Sciences began pressing for the metric system. Yet Congress was content merely to legalize the metric system and allow Americans to adopt the new measures voluntarily—an approach that remains U.S. government policy to this day. America, in Jefferson’s terms, has preferred to mold the law to its citizens, rather than its citizens to the law—at least where commercial interests are at stake.
In America, as elsewhere, even the prospect of the metric system has provoked a nativist response. The humorist Josh Billings mocked the International Metric Convention as a harbinger of universal standardization. “Never,” he wrote, “did so many Kaisers, Kzars, Kings, kum kling knit together in so Klean a Kawse to work so Kommendable a kure.” Others considered the metric system an abomination. Charles Latimer was a devout Christian, a successful railway engineer, and an avid pyramidologist who believed that the “sacred inch” had been built into the Great Pyramid at Giza and had been transmitted across the millennia to the United States. He also had a visceral contempt for atheism, the French, and the metric system. He would even have preferred a Statue of Liberty “measured in good earth-commensurable Anglo-Saxon inches, not in French milli-meters.” No doubt, the antimetric arguments of U.S. industrialists and engineers did more to dissuade Congress in the long run. But Latimer could plausibly boast that he had stopped Congress from passing metric legislation in the 1870s and 1880s.