The Wacky History of Temperature Scales


Many of the scientific concepts we take for granted started as an idea that some guy in a room came up with one day. In this episode, Dan Holohan shares the interesting and peculiar tale of how temperature scales were invented.


Episode Transcript

Many of the scientific concepts we take for granted 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 you'd get stuck because the guys who came up with the concept of measuring temperature hadn’t yet arrived. You couldn't say that it was 100 degrees in the shade. All you could do was mop your brow and shrug. Think about it. 

We base so much of what we do on the temperature inside and outside of our buildings. It's strange to imagine a time before Fahrenheit, and Celcius, and Centigrade.

But since I live in America, let’s talk about Fahrenheit. I’m used to that. I often get very confused when I'm traveling 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 that I left my overcoat at home and the guy on the TV is 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 Celsius, and the freezing point of water 100 degrees Celsius. And he could do that because he was Anders Celsius and it was his scale. So there.

No one uses Celsius these days. We use the Centigrade scale but Celsius often gets credit for it, 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 called zero degrees Fahrenheit the temperature of the coldest stuff he could imagine. That was a mixture of salt and sal-ammoniac. Mix those two things together and it turns into winter. The other fixed point was the normal temperature of the human body, which he called 24 degrees Fahrenheit. He could do that because he was Gabe Fahrenheit. And who's going to argue with Gabe Fahrenheit about the Fahrenheit scale? Feeling chilly? Anyway, on this original Fahrenheit scale, water freezes at 8 degrees Fahrenheit and boils at 53 degrees Fahrenheit.

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.

But here’s where it gets more interesting. Some of the people who were looking at that first mercury thermometer said that the mercury moved very quickly past the numbers and it was difficult to follow. So Gabe solved that problem by giving the scale more numbers. He wanted to keep things simple so he just multiplied everything on the scale by four. This is why water freezes at 32 degrees Fahrenheit and boils at 212 degrees Fahrenheit. 

See what I mean? Nothing scientific about that, right?

Nowadays, your doctor will tell you that the normal temperature of the human body is 98.6 degrees, but on Gabes scale, after he multiplied everything by four, the normal temperature of the human body was just 96 degrees.

So why is it now 98.6? Well, that’s because he’s dead. And once he was gone, all bets were off. He wasn’t around to argue about it anymore.

The fun part of this (at least for me) is that this guy just made all of this up. He wasn’t basing it on anything other than what he decided it should be. That’s all. One guy decided and then everyone else shrugged and went along with it. People are funny that way. You could do the same if you were willing to work as hard at it as Gabe did. Go ahead, establish the Sammy Scale or the Murphy Meter. Knock yourself out. History will remember you forever if you’re willing to work at it.

Think of it. What makes a foot a foot, a yard a yard, a meter a meter, a mile a mile, or pound a pound? Someone just decided and everyone else went along. And that brings up a good point. Is a pound really a pound? And if so, which is heavier, a pound of gold or a pound of feathers? What’s that you say? A pound is a pound? Well that’s not true. A pound is NOT a pound because when it comes to weighing stuff, there are troy pounds and avoirdupois pounds. 

And did you know that a troy pound is lighter than an avoirdupois pound? It is! And that’s pretty amazing because a Troy OUNCE is heavier than an avoirdupois OUNCE. How is that possible? Well, it’s possible because someone said so and everyone went along. So there. 

Do you see what I mean? There’s no science behind any of this. Someone just decided how it was going to be and that was that. The tough part was convincing the rest of us all to go along.

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

In spite of that wacky decision, this became the temperature scale that Russians chose to use for many years. They eventually switched to the Reaumur scale. Monsieur Reaumur sold alcohol thermometers and established the boiling point of water at 80 degrees on his scale. Much of France still uses that scale.

It’s a wonder we ever get anything done, isn’t it?

So who invented the Centigrade scale, which most of the world agrees is the most sensible scale of all? Well, that great accomplishment goes to Carl Linnaeus, a Swedish botanist who also established the modern binomial system of naming plants and animals.
He’s the reason why you and I are both homo sapiens. The Centigrade scale was just something he came up with in his spare time. Imagine that.

So as you’re going through your day, know that there are many things we consider scientific that are actually just the musings of some person sitting alone in a room. There’s nothing magical about any of these people. What’s magical is that so many of us went along with them. Those guys were very good at sales. 

I hope you liked that story. And if you did, share it with your friends, and please subscribe to this podcast. I have many more Dead Men Tales to share with you. And I’m really enjoying the time we’re spending together. You’re a lot of fun! Thanks for being here.

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