Why the metric system is wrong
Author takes 'The Measure of All Things'
By Todd Leopold
(CNN) -- The meter is a crock.
Originally, you see, the metric unit of distance was supposed to be one ten-millionth of the span from the north pole to the equator.
But the Earth isn't a perfect sphere -- it's an oblate spheroid, flattened at the poles -- and every meridian isn't equal because the Earth isn't perfectly smooth, either. So the meter is an average, a compromise -- a figure agreed upon by men, not handed down by nature.
It's arbitrary, in other words.
Which makes the metric system, extrapolated largely from the meter, arbitrary as well. Not as arbitrary as the yard or the cubit or the rod or the mile, but arbitrary nevertheless.
And then there was the error made by one of the surveyors assigned with coming up with a precise measurement for the new unit. That story, and the story of the metric system's creation, is told by Northwestern University history professor Ken Alder in "The Measure of All Things" (The Free Press).
The idea for writing the book goes back to his grade-school days, he recalls in an e-mail interview.
"I remember my fifth-grade teacher instructing us in the metric system and telling us we would need to learn this material because we would all be using it in the future," he says. "I believed her, of course. And when that future failed to arrive I began to wonder why.
"This made me curious about the metric system's past," he continues. "Why had it been created in the first place, [and] why did its creators believe it represented our inevitable future?"
Man vs. nature
As Alder chronicles, the metric system was promulgated by the French Academy of Sciences in the years just after the French Revolution. It was a creature of the 18th-century Enlightenment, when ideas based on science, logic and mathematics were overtaking the world.
In France, the revolutionary governments were determined to take these ideas to their logical conclusions. The country changed to a decimal currency -- an idea that caught on -- and even a decimal calendar, with 10-day weeks, 10-hour days and 100-minute hours -- an idea that did not.
At the time, measures varied from town to town, and were often drawn from human scale.
"This meant that not only were some measures based on the human body ... but that many other measures were based on human labor or on some human evaluation of their worth," Alder says. "Land was measured in days (how many days of labor did it take to reap the harvest?) or in bushels (how many bushels of grain did it take to sow the land?)."
The new French leaders were determined to create a single standard based on the Earth, and assigned two astronomers, Jean-Baptiste-Joseph Delambre and Pierre-Francois-Andre Mechain, to travel the French countryside along the Paris meridian to determine its exact length from the English Channel to the Mediterranean. From that length, the meter would be extracted.
Delambre and Mechain's job wasn't easy. The country was still roiled by politics, transportation could be awkward, and their instruments, though the best of the time, can't compare to today's satellite- and laser-based systems.
Add to the mix the fact that Mechain was a high-strung man who made a mistake in his calculations at one point, then tried to suppress the evidence so as to make the meter conform with expected data.
The two men toiled for seven years. Alder was fascinated by their resolve.
"I consider their mental and moral focus to be a kind of heroism, even if, in the end, the value they finally brought back was less accurate than the estimate they made before they set out," he says. But, he adds, "their powers of concentration ... came at a high human cost. ... The same passion that made Mechain such a remarkable astronomer also drove him to the brink of suicide and madness."
Importance of uniformity
Mechain neglected his family and agonized over his error in letters to others. The irony of the situation was that his mistake didn't matter. The scientists who created the meter wanted it to be close to the commonly used yard (or aune, in France), so Delambre and Mechain's mission was, in many ways, a fait accompli.
"That fiction, however, would have enormous consequences," Alder says. "If the metric system is today used by 95 percent of the people of the world, it is in no small measure due to the 'grand fiction' that the meter was based on nature. ...
"It would hardly have been adopted everywhere if the French had simply 'made it up.' In that sense the expedition proved to be essential to the 'selling' of the metric system, as well as for all the scientific discoveries it unexpectedly produced."
Interestingly, though Alder's book might reveal Mechain's error to a wide audience, it's been commonly known in the scientific community since the mid-19th century. By then, however, the legal definition of a meter had been established, and those who adopted the metric system acquiesced rather than remeasure the earth ad infinitum.
Alder researched the book for seven years, bicycling through the French countryside to get a feel for the surveyors' journey. In many cases, the country roads were still exactly where they were 200 years ago.
His book stresses the importance of a uniform system and how one is developed. In the United States, the reluctance to adopt the metric system caused trouble as recently as 1999, when NASA's Mars Climate Orbiter failed because of a conflict in measurement systems: some engineers used English measurements, others used metric, and determinations were thrown off because of the lack of agreement.
But the growth of a world economy has made Americans "bilingual" in the language of measurement, Alder says.
Eventually, he says, Americans will fully adjust. The metric system was meant to be global, and the meter created by the surveyors has become the worldwide standard.
Yes, the actual length of the meter -- compared with what was intended -- is a mistake. But it's a mistake that has "transformed the world," as the book's subtitle has it.
"That is why," Alder says, "Delambre and Mechain's meter -- created 'for all people, for all time' -- was in fact an error for all people, for all time."