Why the metric system is wrong
Author takes 'The Measure of All Things'
By Todd Leopold
CNN
(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 engineers used English measurements instead of metric. 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."