How Temperature Scales Came To Be

Published: June 17, 2010 - by Dan Holohan

Categories: History Lesson, Darn-Good Stories


Most of the scientific concepts we take for granted nowadays started as an idea that some guy in a room came up with one day. Take temperature, for instance. Before we had thermometers no one knew how hot or cold it was outside. You'd go outside in July and say, "Boy, it's hot today! It must be, what . . . " And there you'd get stuck because the guy in the room hadn't yet given you the concept of temperature. You couldn't say that it was 98 in the shade. All you could do was mop your brow. Think about it; we base so much of what we do on the temperature inside and outside of our buildings. It's it strange to imagine a time before Fahrenheit.

Speaking of whom, I get very confused when I'm in Canada and Europe and someone on the TV tells me it's going to be a lovely 25 degrees on that day. I'm reaching for my overcoat until I realize he's talking Celsius, not Fahrenheit.

And actually, he's not even talking Celsius (even though we often call it that) because we don't use the Celsius scale nowadays. Anders Celsius was the guy that dreamt up that one. It was a long time ago (1742) and he decided to make the boiling point of water zero degrees and the freezing point of water 100 degrees. Hey why not? He was Anders Celsius and he could do what he pleased. His scale, right?

No one uses Celsius. We use the Centigrade scale but Celsius often gets credit, even though he had nothing to do with turning the scale upside-down to get to Centigrade. Doesn't seem fair, does it?

In the U.S., most of us are still swearing by Gabriel Fahrenheit. Gabe was a German merchant and the first guy to make a mercury thermometer. This was also a long time ago, 1721 to be exact. He had to come up with a scale to go along with his new thermometer, of course, and he needed to have fixed points on that scale, so this is what he did. He used as zero degrees the temperature of the coldest stuff he could imagine, a mixture of salt and sal-ammoniac. The other fixed point was the normal temperature of the human body, which he called 24 degrees Fahrenheit. He could do this because he was Gabe Fahrenheit. Who's going to argue the Fahrenheit scale with Gabe Fahrenheit?

Anyway, on this original Fahrenheit scale, water freezes at 8 degrees and boils at 54 degrees. Gabe took his thermometer around and showed it to people who had no concept of temperature measurement (now there's a sales job for you). Some of the people mentioned that the mercury moved very quickly past the numbers on the original Fahrenheit scale, so Gabe decided to give the scale more numbers. He multiplied everything by four and that's why water freezes at 32 and boils at 212. The normal temperature of the human body is actually 96 degrees Fahrenheit but we now call it 98.6 because Gabe is currently on the other side of lawn and not in a position to protest.

The fun part of this (at least for me) is that this guy just made it all up. He could have called it anything and we would have gone along because he was Gabriel Fahrenheit. You could do the same if you were willing to work as hard at it as he did. Go ahead, establish the Schwartz Scale or the Murphy Meter. Knock yourself out. History will remember you forever!

Think of it. What makes a foot a foot, a yard a yard, a meter a meter? Someone just made these up one day, worked really hard, and convinced us all to go along. Why is a troy pound different from an avoirdupois pound? And isn't it amazing that people in different countries can get things done when it comes to engineering?

You say poTAto. I say poTAHto. But how do we all say HVAC?

There was a guy named Delisle who was also into thermometers. He introduced the Delisle scale (ever hear of it?) in 1724. He was following dead on the heels of Gabe Fahrenheit and he, like Celsius, decided to call the boiling point of water zero degrees. He also figured that 100 degrees should be the temperature of a cellar in the Paris Observatory. But on what day? Hmmm.

In spite of that wacky decision, this became the scale that Russia chose to use for many years. They eventually switched to the Reaumur scale. René Antoine Ferchault de Reaumur sold alcohol (not vodka) thermometers and the boiling port of water was 80 degrees on his scale. Much of France still uses this scale. Did you know that?

Isn't it amazing that we all managed to get where we got?

So who invented the Centigrade scale, which most of the world agrees is the most sensible scale of all? Well, that feat goes to Carl Linnaeus, a Swedish botanist who also established the modern binomial system (genus plus species) for naming plants and animals. The Centigrade scale was just something he came up with in his spare time. Imagine that.