The metric system is a bad idea. Jacob Levy notes in a post responding to Kevin Drum that it is emblematic of a bigger debate: The French Revolution vs. Classic Liberalism, Robespierre and Napoleon versus Montesquieu and De Tocqueville.
I've also become pretty enmeshed in the intra-French debates about measurement. In the
old regime hundreds of different systems of weights and measures existed in France,
often imposed by local law and often using the same names for units that had very
different sizes elsewhere. How one saw this mess, and what one thought was the
appropriate response to it, are very important markers of general intellectual position
on a set of issues I'm interested in, with the philosophes and Napoleon on one side,
Montesquieu and Constant on the other. It was that intra-French variety that made the
need for a new system seem so urgent, though its proponents always talked about bringing
reason to the whole world. Where there wasn't such intra-French confusion (i.e. with the
calendar), the Revolutionary attempt to remake things didn't stick.
Recall the second of Russell Kirk's Canons of
Conservatism
Traditional life is filled with variety and mystery while most radical systems are
characterized by a narrowing uniformity.
Professor Levy takes a sensible position on the metric system: Centigrade is clearly
worse than Farenheit from a practical point of view, but the others don't matter much.
Farenheit has two advantages: 1. It measures temperatures to be positive over the
ordinary range of weather, rather than having to go negative in wintertime, and 2. Its
units are a more sensible size going from 0 to 100 over the useful range rather than
wasting most of its 0-100 range on temperatures not used for weather. Farenheit's
advantage is contextual: for cooking, Centigrade might be better; for astronomy, Kelvin
(which starts at absolute zero) might be better.
It is actually no accident that the Farenheit scale has these advantages. Here's one rendition of the story I've heard:
On the other hand, he (first) defined 0� as the lowest temperature he could achieve in
the laboratory by using salt to melt ice. (Although it's, in fact, possible to go a few
degrees lower by doing the same experiment under ideal conditions.) This same
temperature was also then a record low for Danzig (in 1709).
These two points, however, were later judged to be far too imprecise a basis for a
temperature scale. Instead, it was decided that the ice point would be exactly 32�F and
the steam point 212�F.
Temperature scales should be based on two temperatures that are easily reproducible in
any lab. The fahrenheit scale is based on the lowest temperature that can be reached
with a mixture of snow, ammonium chloride, and alcohol (called 0 degrees), and average
human body temperature (called 100 degrees). According to legend, Mr. Fahrenheit did
not sample the temperature of many people (he used his wife!), so his 100 degree mark is
a little high. More likely, the 100 degree mark was adjusted to make the melting point
of ice an even 32 degrees F, and the boiling point of water was 212 degrees F.
Here is what may
be a more accurate telling:
Between 1700-30, Fahrenheit produced several accurate mercury thermometers. He called
the temperature of an ice/salt mixture "zero degrees", as this was the lowest
temperature he could conveniently attain in his lab and called his own body temperature
"96 degrees", and then divided the scale into single degrees between 0 and 96. On this
scale, the freezing point of pure water happens to occur at 32 (and the boiling point at
212). After Fahrenheit died in 1736, scientists calibrated his model of thermometer
using 212 degrees as the upper fixed point. When the Fahrenheit thermometer was
recalibrated, normal human body temperature registered at 98.6 rather than 96.
And here is a
third telling:
In 1714, when G.D. Fahrenheit devised the temperature scale now named after him, he
meant 100� to be the normal temperature of the human body.
It's funny how the web shapes us. If I had not had the web, I would have just told the
story of 0 and 100 being the lowest-lab and ordinary-human temperatures from memory, or
I would have gone to my bookshelf and found what Isaac Asimov had to say, since I'm sure
he has an essay on this somewhere. But I didn't, since I have Google.
Returning to political philosophy, note how different the origins and spreads of
Farenheit and Centigrade are. Farenheit was invented to be useful, and was; Centigrade
was invented to fit neatly with physical constants, and didn't (science was not
advanced enough and the match to physical constants wasn't quite right). Farenheit
spread, I guess (I don't know for sure) because people voluntarily adopted it in the
marketplace of ideas, with Farenheit beating out competitors such as Reamur's scale.
Centigrade spread by threat of violence-- government force-- under the mask of progress
and enlightenment.
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