Degree of Frost

We usually think of a temperature scale as proceeding from a zero point with higher numbers corresponding to hotter temperatures, and indeed that is probably the most intuitive way to think about it, but that’s not necessarily the case; “degrees of frost” are, or at least were, used in contexts where temperatures were normally below the freezing point. According to Wikipedia they attained their greatest currency during the Heroic Age of Antarctic Exploration around the turn of the 20th century. Either Celsius or Fahrenheit degrees could be used. For Fahrenheit degrees they’re counted up with every degree below +32 degrees, e.g. +20 degrees Fahrenheit is 12 degrees of frost, -10 degrees Fahrenheit is 42 degrees of frost, etc.

Retvrn to OG Celsius!

In the case of Celsius degrees “degrees of frost” are simply the negative degrees that characterize temperatures below the freezing point, only with their signs flipped to be positive instead of negative. Weirdly enough, this inverted scale, with higher numbers corresponding to colder temperatures, was actually the original version of the Celsius scale! Anders Celsius’s original temperature scale in 1742 fixed 0 degrees at the boiling point of water, and +100 degrees at the freezing point. It was Jean-Pierre Christin who first inverted the centigrade scale to its present version in 1743, more or less independently of Anders Celsius’s work.

Degrees of Frost: particularly Compelling on Argon-Snow Worlds?

“Degrees of frost”, or more generally a system where you count up as it gets colder instead of down, might seem weird, but it may well make sense in a more cryogenic environment where temperatures are normally below freezing, perhaps well below freezing, as is the case in Antarctica. Even then, if you’re, say, a methane-drinking life-form on Titan, a scale with just a lower zero point, perhaps the freezing point of methane instead of water, would make more sense, but what if you’re in an environment with extreme seasons, like some worlds I’ve speculated about in a science-fictional context, where summers are still temperate, permitting life as we know it to thrive, but winters are extremely cold?

In particular, I wonder if it would make sense to use a degree of frost scale on a world that experiences distinct kinds of snow, let’s say a first snow season (in autumn) consisting of water ice and a second snow season (in winter) consisting of argon ice, like I’ve speculated about recently. The denizens of such a world might find it intuitive to set the zero point at the freezing point of water, as in our centigrade scale, but set the other positive pole of the scale at the freezing point of argon, quite a bit colder.

This system on such a world would have unique advantages. Let’s say the freezing point of argon is defined as +100 degrees. Then negative temperatures correspond to the liquid water range, single- and double-digit positive temperatures correspond to the water-ice range, and triple-digit positive temperatures correspond to the argon-ice range. If you have three distinct phases of precipitation in your world’s climate such a system may well catch on.

If you set the degree interval to be one-hundredth the interval between argon’s and water’s freezing points, then each degree on this scale would correspond to 1.892 Celsius degrees, or 3.4056 Fahrenheit degrees. Those are big degrees by our standards, but in a world where temperatures can vary by 400 degrees Fahrenheit in an average year the small-scale temperature changes we’re sensitive to might pass people by.

If such a world has summers similar to Siberia’s, then the hottest day in an average year might be on the order of 80 or 90 degrees Fahrenheit. That’s -30 Fahrenheit degrees of frost, or roughly -10 degrees in the argon-water-reverse-centigrade system. Hmm…that’s a mouthful, that phrase; if the world I speculated about recently indeed has ice dragons, maybe they could call them ice degrees or dragon degrees or some such. I don’t know.

Anyway, an interesting feature of this system is that “absolute zero” puts a ceiling on how high the positive degree numbers can go. In degrees Fahrenheit of frost it’s 491.67 degrees, in degrees Celsius of frost it’s 273.15 degrees. In degrees dragon of frost (heh) it would be 144.37 degrees.

Milligrade instead of Centigrade?

Big degrees might make sense in a world with big seasonal swings, but argon-water-ice degrees are big enough to potentially make a milligrade scale catch on instead of a centigrade scale. Already for most precise applications, even everyday meteorological reports of temperature, it’s customary to quote the Celsius temperature to a tenth of a degree, with is de facto milligrade rather than centigrade bar the placing of the decimal point. If we moved from centigrade to milligrade, as has actually been proposed by one blogger, the boiling point of water would be 1000 degrees rather than 100 degrees, and weather reports would use whole numbers.

In the milligrade version of the argon-water-ice system, one degree would be equal to 0.1892 Celsius degrees, or 0.34056 Fahrenheit degrees. Absolute zero would lie at +1443.7 degrees. The hottest days in midsummer would lie at around -100 degrees, the coldest days in midwinter modestly above +1000 degrees. Now that’s an interesting possibility.

The Metric Principle with different Number Systems

Of course if you’re talking about an alien culture or even a human one far from our modern Western sphere of influence it’s entirely possible they’re not using a base-10 number system, and so their form of metric would be based around different powers other than 10. For instance, a duodecimal system would be based on powers of 12. A duodecimal centigrade scale would be sliced into 144 increments (12*12) rather than 100 (which is 10*10). A sexagesimal (base-60) metric system would divide its centigrade scale into 3600 degrees (60*60). And of course it’s possible they don’t use the metric principle at all. I touch on different number systems in another post.


All this is a bit specific of a topic, I’ll admit, but I came across the “degrees of frost” thing today and found it interesting. I think especially if you’re worldbuilding or writing a story for a cryogenic medieval fantasy style environment using degrees of frost, especially degree intervals wildly divergent from our own, can really help to lend your world some character. And of course as the Heroic Age of Antarctic exploration proves there are quite a few other applications for the principle as well.

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