Walfredo Cirne


The fact the world uses two temperature scales has always bothered me.

Why not use the brilliant °C system? 0°C = water freezing. 100°C = water boiling. Clean, simple, elegant! And even practical! 0°C is a temperature that many humans live with, making it ease for people to have a sense of it.

°F in contrast, has freezing as 32°F. Water boiling is 212°F. 100°F is the temperature of someone slightly ill. Completely arbitrary, isn’t it?

But there must have been a reason for °F. Someone, I imagine a smart early scientist, thought of it. There must be an explanation.

Decided I to find out, I searched the Internet. :-)

Fahrenheit: Thermometer scale in which the freezing point of water is 32°F and the boiling point of water 212°F.

The Fahrenheit scale is still obstinately in use in the US. This anachronism requires conversion from Centigrade (°C) to Fahrenheit (°F), and vice versa.

One degree °C = (5/9)(°F - 32).
One degree °F = (9/5)(°C) + 32.

Named for Gabriel Fahrenheit, a German-Dutch physicist, who devised the scale in 1724. 0°F was the lowest temperature that Fahrenheit could obtain using a mixture of ice and salt.

It doesn't make sense, does it? Why someone presumably smart would pick "the freezing point of water is 32°F and the boiling point of water 212°F"?

After much thought, I believe the key for this mystery is that 100°F is the temperature of someone slightly ill. I think the idea was for 100°F to be the average temperature of a human being, which of course is not the best, reproducible reference for you to anchor your temperature scale. But the idea behind it was good: 100°F being body temperature. Today, we know this is 37°C = 98.6°F.

So… we could think of a temperature scale that combines the best of °C and °F.

Natural Degrees = °N!!!

0°N = freezing water. 100°N = average human body. 0°N = 0°C = 32°F. 100°N = 37°C = 98.6°F. This way both 0 and 100 have practical meaning, temperatures that we can relate to in daily life. 0 After all, boiling water may be a nice place for you to anchor your temperature scale, but is not a temperature we experience at all. By the way, boiling water = 270°N.

And °N are quite intuitive. As the name suggest, they fell natural. Around 70°N is great weather, over 100°N is hot, near 0°N is cool. In general, near 0, °N behaves like °C. Near 100, °N is like °F. All in all, a perfectly reasonable and intuitive temperature scale.

(If you wanna give it a try, the formulas are °C =  37/100°N, °N = 100/37°C  , °N = 500/33(°F - 32), and °F =  333/500°N + 32. And the temperature scales °F and °N intersect each other at 95.8°F = 95.8°N. Of course, by definition, 0°N = 0°C. And, as everybody knows, -40°C = -40°F ... Sorry! Got carried over! :-)

Anyhow, where were we?

Ah, right! When °N become the dominant temperature scale, we can introduce °NK, the Natural-Kelvin. You know, K = Kelvin, the scientific scale. (How come K is not °K?? the ° is gone?!? haven’t people heard of orthogonality?!?)

Anyhow, 0K is absolute zero. The lower possible theoretical temperature, where there is no movement of atoms... or something like that. :-) But, of course, you need two places to anchor a temperature scale. Kelvin people did (x+1)K - xK = 1°C or, equivalently, xK - yK = x°C - y°C. In English: that K increase at the same speed as °C. This means that 0K = -273.15 °C. Therefore, 0°C = 273.15K and 100°C = 373.15K.

So... you guessed!  x°N - y°N =  x°NK - y°NK, or °NK increases at the same pace as °N. (We are, of course, keeping things orthogonal… :-) Therefore, 0°N = 738.24°NC, and 100°N = 838.24°NC, and the formulas and interesting values ...

Well, never mind!! Two common use temperature scales are already too many. :-) Better leave things as they are... Moreover, it could give someone the idea that Rankine Degrees = °R are actually a reasonable idea. :-)