The Real Heat Miser and Snow Miser

In The Year Without a Santa Claus, Mother Nature has two sons who cannot be in a room together. Snow Miser freezes what he touches. Heat Miser melts it. They each want the whole world, they settle for half, and the entire plot is two brothers refusing to compromise about the temperature.

The real ones were called Fahrenheit and Celsius. Their lives overlapped. And between them they did precisely what the cartoon describes: split the planet down the middle, and we have never got it back.

Celsius put one hundred at freezing

Start here, because everything follows from it and almost nobody knows it.

Anders Celsius published his scale in 1742. Zero was the boiling point of water. One hundred was freezing. Not a misprint and not a rumour — that is the scale he built, and the scale he used until he died in 1744. What the world calls Celsius today runs the opposite direction to the thing Celsius actually made.

Someone turned it over in 1745, the year after he was buried. Probably Carl Linnaeus, the botanist who spent his career putting things in the correct order, though the records are murky enough that it may have been Daniel Ekström, who manufactured the thermometers and presumably had views about which way up they ought to read.

Sit with the original for a second, though, because it tells you something the corrected version hides.

Nobody designing a thermometer for a person puts freezing at one hundred. Nobody hangs that on a porch. It only makes sense if you are not thinking about porches at all — if what you have in your hands is a flask, and the question you are asking is how far a substance is from its transitions. Celsius was an astronomer running an observatory in Sweden. He built an instrument for the work in front of him, and the work in front of him was not is it cold out.

Fahrenheit anchored his to a bucket and a body

Daniel Gabriel Fahrenheit published eighteen years earlier, in 1724, and made completely different choices — which is the interesting part, because you can reason backwards from a choice to the person it was for.

He needed a zero that anyone could reproduce, so he mixed water, ice and ammonium chloride into a brine and took the coldest thing he could reliably make in a workshop. That is zero. Not an absence of heat, not a natural floor. The bottom of a bucket of salty slush, because he could hit it again on Tuesday.

Then he needed an upper mark, and he used his own body. He called it ninety-six.

Ninety-six is the detail I cannot let go of. It is not ninety-six because anyone counted ninety-six of anything. It is ninety-six because ninety-six divides into twelve parts of eight, so the scale could be ruled onto glass by halving, and halving, and halving again. The most-quoted number in human health for two centuries was picked for its factors.

But look at what he reached for. A bucket he could mix and a body he was standing in. Both referents are in the room with him. Celsius reached for the two phase changes of water, which are the most reproducible pair on earth and are not in the room with anybody.

Which is why Fahrenheit is the more intuitive scale, and it is not close

This is the argument that never gets made properly, because it always turns into a fight about metric.

Zero to one hundred Fahrenheit is very nearly the whole band a human being experiences weather in. Zero is a brutal day. One hundred is a brutal day in the other direction. Ordinary life fills the middle, in whole numbers, without a minus sign in sight. The scale has a hundred usable gradations across exactly the range a person has opinions about.

Now do the same in Celsius. Human weather occupies roughly minus twenty to forty. Sixty degrees of usable range, half of it negative, inside a scale whose full hundred points are reserved for the interval between ice and steam — a span you will encounter in a kettle and essentially nowhere else.

That is not a defect. It is a scale doing its job. Water freezing and water boiling are exactly the marks you want if you are a chemist, and the reason the world runs on Celsius is that the world eventually decided science should set the units. Fair enough.

But it does mean most of humanity checks the morning temperature on an instrument built for a laboratory, and a minority checks it on one built for a man standing outside wondering how cold it is. Only one of those was designed for the question being asked.

And Fahrenheit won where he won for a reason that has nothing to do with any of this

Here is the fact that ought to end every version of this argument and never does.

Fahrenheit’s scale did not spread because it was better. It spread because his thermometers were better. He had worked out how to build a mercury-in-glass instrument that was accurate, repeatable and worked across a wide range, at a time when everybody else was fighting with alcohol. People bought the instrument. The scale came free in the box.

Three centuries of national identity, sitting in a drawer, because one man was a better glassblower.

Neither of them discovered anything

Every few months the internet runs the argument again, and both sides talk as though one of these scales is correct and the other is an error some country refuses to own up to.

There is nothing to be right about. One man anchored his numbers to a brine and a body and chose his top figure because it divided nicely. The other anchored his to water and ran it upside down, and had to be corrected after his death by a taxonomist or a salesman, nobody is sure which. Neither found a boundary sitting in nature waiting to be labelled. They decided, wrote it down, and stuck to it.

Which is the entire source of a scale’s value, and the part nobody sings about. Not truth — agreement. A convention earns its keep by being published, applied the same way every time, and open to anybody who wants to check the working. Fahrenheit’s zero is arbitrary and it is also exactly as cold on every occasion it is invoked, which is the whole of the point. Celsius is arbitrary and upside down from its author’s intention and it still lets a chemist in Osaka and a chemist in Lagos mean the same thing by the same number.

The arbitrariness is not the flaw. The arbitrariness is unavoidable. The discipline is what matters.

Mother Nature’s sons

The cartoon ends with the brothers agreeing to trade — one day each in the other’s territory, as a favour to their mother. It takes Santa’s near-retirement and a musical number to get them there.

Fahrenheit and Celsius never got that scene. One died in 1736 and the other in 1744, and neither lived to see what the argument would turn into, which is probably a mercy. We are still doing the bit. Mister Green Christmas and Mister White Christmas, three hundred years on, in the comments.

And both of them, it turns out, were making it up as they went — carefully, repeatably, and entirely on purpose.

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Sources: the 1742 scale with zero at boiling, and its reversal in 1745 —
Anders Celsius and
Celsius. Fahrenheit’s brine zero, the ninety-six-degree body mark and the mercury thermometer —
Daniel Gabriel Fahrenheit and
Fahrenheit. On Celsius’s legacy,
JSTOR Daily.
The Misers are Rankin/Bass, The Year Without a Santa Claus (1974) — the verses above are mine, to their tune, and not their words.