Solon Economou

Just when is it "cold"?

Below zero isn't what you think it i

We New Englanders are so used to cold weather that many of us have fallen into the trap of not thinking it's "cold" till the temperature is "below zero."  We can thank German physicist Daniel Fahrenheit for that, who proposed his screwy Fahrenheit temperature scale back in 1724.

I call this a "screwy" scale--I won't even get into how he devised it, but if Rube Goldberg delved into chemistry, this was it.  In Fahrenheit's scale, the freezing point of water comes out to 32 degrees Fahrenheit, and the boiling point at 212 degrees, a total of 180 planned degrees between the two.   Therefore, zero degrees Fahrenheit is actually 32 degrees below freezing.  It is actually pretty damn cold at "below zero."

I have nothing against screwy scales as long as they make some kind of sense.  I love the English system of measurement, where we think in terms of inches and feet and yards and miles, while most of the world thinks in terms of the metric system of centimeters and meters and kilometers, etc. 

The metric system is based on actual measurements of the Earth and has a very rational basis.  The English system--well, I loved teaching that in physics class.  Traditionally, the foot was based on the length of the king's foot.  As my physics students used to say, "Of course.  They got it from a ruler."  The inch was purportedly based on the length of the king's thumb from the middle joint to the tip.  And so it went for the rest of English metrics.  For a little bit of fun, I would occasionally have my physics students calculate speed in "furlongs per fortnight."

In the temperature category, Fahrenheit got the jump on things in 1724, and his screwy system was in vogue before Andre Celsius, a Swedish astronomer, came up with the centigrade scale in 1742.  The centigrade scale, as the name implies, divides the temperature range into 100 degrees between the freezing and boiling points of water, zero being the freezing point and 100 being the boiling point, making a very rational temperature scale.  Degrees in this scale are called "degrees centigrade" or "degrees Celsius," in honor of old Andre.

A fact that very few people know (the number now includes you) is that Celsius developed the scale backward, from 100 degrees freezing to 0 degrees boiling.  In 1744, a Swedish botanist, Carolus Linnaeus, said "That's nuts, Andre," and reversed it so that freezing was at zero and boiling was at 100.

In Europe, when the temperature is zero, they know it's cold.  In America, we practically think it's warm at 32, which is the same temperature.

Let's see how the two scales compare:

Degrees F          Degrees C

212                       100              (boiling point of water)

72                         22

40                         4

32                         0                   (freezing point of water)

0                          -18

-10                       -23

I'd just as soon drop Herr Fahrenheit's misleading scale altogether and forever.  When the water turns to ice, I want that to be at zero, not 32.

Now did I mention there are also two more temperature scales, both used in science, the Kelvin and Rankine scales?  Can I expound on those?  Do you have time?  Let's get some coffee...