The Marginalian
The Marginalian

The Measure of All Things: How Two French Astronomers Nearly Lost Their Lives Revolutionizing the World with the Invention of the Meter

The Measure of All Things: How Two French Astronomers Nearly Lost Their Lives Revolutionizing the World with the Invention of the Meter

In her memoir, the trailblazing astronomer Caroline Herschel recounted frequently having to “measure the ground with poles” when she first began making astronomical observations in the 1780s. It seems odd that something as grand and lofty as studying the heavens would necessitate something this humble and earthbound, but this seemingly mundane task is important for two reasons — it reminds us that astronomers were the original measurers of everything we know, but it also raises the question of what the ground was measured in. For it wasn’t until a generation later that the measures of the world were standardized, thanks to the French astronomers Pierre Méchain and Jean Baptiste Joseph Delambre, who set out to unite humanity by creating a single measure: the meter, arguably the most impactful mathematical concept since the invention of zero, central to everything from the speed of light and our basic understanding of the universe to the daily practicalities of shoe sizes, doorframe dimensions, and driving speed limits. Over and over during their seven-year quest for peace through mathematical perfection, they stumbled and fell and got back up, nearly losing their heads to the guillotine on multiple occasions as they toiled to create an equalizing measurement that would “encompass nothing that was arbitrary, nor to the particular advantage of any people on the planet.”

Jean Baptiste Joseph Delambre and Pierre Méchain

Historian Ken Alder tells the story of Delambre and Méchain’s ambitious, improbable, and heroic feat in The Measure of All Things: The Seven-Year Odyssey and Hidden Error That Transformed the World (public library). He casts the stakes:

In June 1792 — in the dying days of the French monarchy, as the world began to revolve around a new promise of Revolutionary equality — two astronomers set out in opposite directions on an extraordinary quest. The erudite and cosmopolitan Jean-Baptiste-Joseph Delambre made his way north from Paris, while the cautious and scrupulous Pierre-François-André Méchain made his way south. Each man left the capital in a customized carriage stocked with the most advanced scientific instruments of the day and accompanied by a skilled assistant. Their mission was to measure the world, or at least that piece of the meridian arc which ran from Dunkerque through Paris to Barcelona. Their hope was that all the world’s peoples would henceforth use the globe as their common standard of measure. Their task was to establish this new measure — “the meter” — as one ten-millionth of the distance from the North Pole to the equator.

The meter would be eternal because it had been taken from the earth, which was itself eternal. And the meter would belong equally to all the people of the world, just as the earth belonged equally to them all. In the words of their Revolutionary colleague Condorcet — the founder of mathematical social science and history’s great optimist — the metric system was to be “for all people, for all time.”

Indeed, there was a larger kind of idealism beneath the quest for mathematically precise measurement:

To do their job, standards must operate as a set of shared assumptions, the unexamined background against which we strike agreements and make distinctions… Our methods of measurement define who we are and what we value.

When Einstein spoke of “the common language of science,” he was animated by a similar humanistic vision of shared values. But in the eighteenth century, measures differed so widely from nation to nation that they produced practically the same stumbling block for cooperation, communication, and commerce as different languages. Worse yet, the discrepancies made it impossible for scientists — or “savants,” as scholars of nature were known in that era — to compare notes and build upon one another’s work.

Alder considers the monumental legacy of Delambre and Méchain’s troubled triumph:

For seven years Delambre and Méchain traveled the meridian to extract this single number from the curved surface of our planet. They began their journey in opposite directions, and then, when they had reached the extremities of their arc, measured their way back toward one another through a country quickened with revolution. Their mission took them to the tops of filigree cathedral spires, to the summits of domed volcanoes, and very nearly to the guillotine. It was an operation of exquisite precision for such violent times. At every turn they encountered suspicion and obstruction. How do you measure the earth while the world is turning beneath your feet? How do you establish a new order when the countryside is in chaos? How do you set standards at a time when everything is up for grabs? Or is there, in fact, no better time to do so?


The results of their labors were then enshrined in a meter bar of pure platinum. It was a moment of triumph: proof that in the midst of social and political upheaval, science could produce something of permanence. Accepting the fruit of their labor, France’s new supreme ruler made a prophesy. “Conquests will come and go,” Napoleon Bonaparte declared, “but this work will endure.”

And yet no idyll is ever complete — although, two centuries later, more than 95% of humanity uses the metric system, the world’s alleged greatest superpower does not. Thomas Jefferson was the first to attempt persuading Congress to adopt the meter, which would’ve made the United States the second country after France to pioneer the universal measurement. He failed, as did every reformer since. The costs of that failure are many, but none more tragicomically obvious than the 1999 loss of the Mars Climate Orbiter — the $125-million space probe that went missing, literally lost in translation, after one team of engineers used the metric system and another American units.

Perhaps the central paradox of all progress is that we are a species bedeviled by inescapable ambivalence. Science, after all, is “a truly human endeavor,” susceptible the same human folly of ambivalence even in its quest for objective truth. Alder reflects:

Behind the public triumph of the metric system lies a long and bitter history. The fundamental fallacy of utopianism is to assume that everyone wants to live in the same utopia.

In the remainder of the thoroughly fascinating The Measure of All Things, Alder goes on to chronicle the inadvertent errors, deliberate deceit, and other fragments of fallible humanity that marked this monumental quest for scientific perfection. What emerges is less a story about pure science than one about a central foible of being human — about why we make mistakes, about our moral vacillation between covering them up and amending them, and about how we reconcile our idealism with our imperfection.

HT It’s Okay To Be Smart

Published March 22, 2017




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