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Dear Cecil:
Everybody knows 0 degrees on the Celsius scale is the freezing
point of water and 100 degrees is the boiling point. On the
Fahrenheit scale, however, freezing is 32 degrees and boiling 212.
How on earth were these numbers arrived at? Do 0 and 100 degrees
Fahrenheit mean anything? --Leslie, Montreal, Quebec
Cecil replies:
Researchers have gone to their graves trying to figure out what old
man Fahrenheit was up to, Leslie. Here's the story as well as I can
piece it together:
Daniel Gabriel Fahrenheit (1686-1736) was a German instrument maker
who invented the first practical mercury thermometer. Casting about
for a suitable scale for his device, he visited the Danish
astronomer Ole Romer, who had devised a system of his own.
As it
turned out, it was a case of the blind leading the blind.
Romer had decided that the boiling point of water should be 60
degrees. This at least had the strength of numerological tradition
behind it (60 minutes in an hour, right?).
But zero was totally
arbitrary, the main consideration apparently being that it should
be colder than it ever got in Denmark. (Romer didn't like using
negative numbers in his weather logbook.)
In addition to the
boiling point of water, the landmarks on Romer's scale were the
freezing point of water, 7-1/2 degrees, and body temperature,
22-1/2 degrees.
D.G., simple soul that he was, thought this cockeyed system was the
soul of elegance. He made one useful change: to get rid of the
fractions, he multiplied Romer's degrees by 4, giving him 30 for
the freezing point and 90 for body temperature.
Then, for reasons
nobody has ever been able to fathom, he multiplied all the numbers
by 16/15, making 32 freezing and 96 body temperature. Boiling point
for the time being he ignored altogether.
By and by Fahrenheit got ready to present his scale to London's
Royal Society, the scientific big leagues of the day.
It dawned on him that it was going to look a little strange having
the zero on his scale just sort of hanging off the end, so to
speak. So he cooked up the explanation that zero was the
temperature of a mix of ice, water, and ammonium chloride.
At some point Fahrenheit figured out that the boiling point of
water came in at 212 degrees. Over time this replaced body temp as
the upper landmark on his scale. Meanwhile, as more precise
measurements were made, body temperature had to be adjusted to 98.6
degrees.
In short, 100 means nothing at all on the Fahrenheit scale, 96 used
to mean something but doesn't anymore, and 0 is colder than it ever
gets in Denmark. Brilliant.
Lest we get too down on Fahrenheit,
though, consider Anders Celsius, who devised the centigrade scale
(0 to 100).
Everybody agrees Celsius's scale makes more sense than
Fahrenheit's. Trouble is, the original Celsius scale had 100 for
freezing, 0 for boiling. In other words, it was upside-down. (The
numbers were reversed after Celsius's death.)
These thermometer guys, what gets into them? Must be too much mercury exposure.
OK, you're saying, very interesting. But what I REALLY need is a temperature trivia question that will make me
the life of the party.
I have just the thing. At what temperature are the Fahrenheit and
Celsius readings the same? People will look at you with newfound
respect when you reveal the astonishing answer: minus 40.
--CECIL ADAMS
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