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The metric system: inspired by revolution

The Story

It's a tale worthy of the title "Indiana Jones and the metre," says science writer Stephen Strauss. After the 1789 French Revolution, the French wanted to create a new measurement system based on something scientific, rather than the whims of the ruling class. So two surveyors were sent out to measure "one-ten-millionth of a quadrant of the great circle of the earth" - the distance that would become the metre. In this clip, Strauss describes the adventures the surveyors encountered in completing this mammoth task. Strauss also tells Quirks & Quarks about early opposition to the metric system and France's failed attempt to institute a system of "metric time." Overall, he says, the prevalence of the metric system in the world today means that "science triumphed." 

Medium: Radio
Program: Quirks & Quarks
Broadcast Date: April 8, 1995
Guest(s): Stephen Strauss
Host: Bob McDonald
Duration: 7:54

Did You know?

• Systems of measurement have varied and evolved throughout history, and they were often quite imprecise in the past. The ancient Egyptians, Greeks, Jews and Romans each had their own systems of measurement but they were all primarily derived from body measurements. The ancient Egyptian zebo was based on the width of a finger, for example, while the ancient Hebrew tefach was the width of a palm.

• According to the Oxford Dictionary of Weights, Measures, and Units, the British imperial system was made the official system for Britain in 1824. The system itself had, however, been evolving for centuries. Legend has it that the modern yard - the standard on which all imperial lengths are based - was based on the distance between the nose and fingertips of the outstretched arm of King Henry I of England (who reigned from 1100-1135).

• Before the French Revolution, France's system of measurements was quite similar to the British system, according to Gerald Black's 1974 book Canada Goes Metric. But as Black explains, the post-Revolution government "wanted to create a new France devoid of all the shortcomings which were so typical of the previous government." Among the sweeping changes were a new flag, the abolishment of old royal titles, the reorganization of France into electoral provinces, and the establishment of a new measurement system.

• After establishing the length of the metre (derived from the surveyors' measurement of the earth), it was decided that all other units of the system would be based on multiplying or dividing by 10. The math would be very easy: 1/1000 of a metre = one millimetre, 10 millimetres = one centimetre, 10 centimetres = one decimetre, 10 decimetres = one metre, 10 metres = one decametre, 10 decametres = one hectometre, and 10 hectometres = one kilometre.

• Other types of measurements were also based on the metre. For measurements of mass, one gram is equal to the mass of one cubic centimetre of pure water. And for volume, a litre is equal to one cubic decimetre. As Black explains in Canada Goes Metric, "Here we have length, volume and mass interlinked as never before in the history of measurement."

• Interestingly, the original measurement that the metre was derived from was later found to be wrong. The surveyors measuring the distance of a quadrant of the earth were slightly incorrect, so the metre is actually two-tenths of a millimetre off. In 2002, historian Ken Alder wrote a book on the drama surrounding this inaccuracy, called The Measure of All Things: The Seven-Year Odyssey and Hidden Error that Transformed the World.

• According to Alder's book, the mistake and a subsequent attempt to cover it up nearly drove one of the surveyors responsible for the measurement to kill himself.
• Despite the inaccuracy, the length of the metre remains the same today as it was in the 18th century. The definition was subsequently changed by scientists, however, to preserve the integrity of the measurement. It's now defined as the distance travelled by light through a vacuum in one-299,792,458th of a second.

• In a 2002 National Post article about Alder's book, the author says it doesn't really matter that the measurement was wrong, since it was the idea of the metre that appealed to people. Alder says it seems absurd to go to such great lengths to get something that was almost the same as a yard, but politically, it was a smart move. "It turns out the brilliance of basing it on the size of the world worked. It was a fiction that succeeded."

• The Celsius temperature scale wasn't developed by the French at the same time as the rest of metric. It was actually created by Swedish astronomer Anders Celsius in 1742. But because it's based on the number 100 (with zero as the freezing point of water and 100 the boiling point), it was adopted by metric countries and is now considered a part of the metric system.


For Good Measure: Canada Converts to Metric more