Monday, January 21, 2013

A partial defence of the Fahrenheit System

Like anybody raised outside the US, the metric system of measurements seems self-evidently better than the ludicrous imperial system. The advantages were best summed up by a French friend of mine, who said ‘Tell you what, I’ll convert to the imperial system when you can tell me without a calculator or pen and paper how many ounces there are in 4.256894 imperial tons.’ The point being, of course, that it’s trivially easy to work out how many grams there are in 4.256894 metric tonnes, because everything divides through by 10.

So you don’t have to sell me on the general principle here. But true to a slight contrarian streak (The Couch: “Slight”? Are you kidding me?) I feel compelled to advance some of the better but more overlooked arguments. A company may be good in fundamentals but still overpriced, and the same logic applies to arguments.

For the Fahrenheit/Celsius distinction, the difference is less material. We find it pleasing for round numbers like 0 and 100 to be associated with important physical phenomena like water boiling and freezing. But this really is just an aesthetic point, because you could just as easily subdivide 1F into sub-units as 1C. It’s not clear that anyone has ever proposed converting all the other units of weights and measures to metric while retaining the Fahrenheit scale of temperatures, but as far as I can tell it wouldn’t make scientific calculations obviously any harder (besides needing to re-learn the physical constants in different units, which is a one-off cost for any proposed change).

One benefit of the Fahrenheit system is that the unit of measurement is smaller – 4/9 smaller, to be precise. This isn’t inherently useful, but it does mean that more information is conveyed over the range of temperatures that you typically observe.

For instance, take the example of a car thermostat (which first got me thinking about this problem). The air conditioner in my house back in Australia lists the temperature in degrees Celsius. While the range of temperatures out in the real world is pretty large, the range of temperatures that cover 95% of my air conditioner use is essentially 19C to 25C. What this means is that I’m given 7 useful temperature settings. Which, most of the time, is fine.

But if I’ve got a Fahrenheit thermostat (which I do in my US car), this gives me 12 useful settings from 66F to 77F.

Now, I know the likely objection- “Come on, can you really tell a difference of 1 degree Fahrenheit?”
To which I respond, “Truthfully, if you gave me a blind temperature test, I don’t know - maybe some of the time, maybe not. But here’s the flip side – 1 degree Celsius is calculated as 1/100th the difference between the freezing temperature of water at sea level and the boiling temperature of water at sea level. What on earth makes you think that this amount is also magically equal to the smallest temperature difference that humans can discern? Is there any evidence for this proposition at all?”

I found myself thinking about this when I realized that after several years of driving, I tended to automatically adjust the thermostat in units of 2 Fahrenheit. Subconsciously, I was thinking of temperature changes of roughly 1C, and just ignoring the odd numbers. And then it occurred to me that this made absolutely no sense at all. While I’m not some sensitive ninny, there were times when you really did feel marginally more comfortable at 73F than 72F or 74F.

This may just have more to do with the nature of air conditioners, where they are more likely to have a logic of ‘always turn on when temperature is above X and go at full bore until temperature drops below Y’, where X and Y are some tolerances around whatever you set the dial at. If you really could keep the temperature truly constant, it perhaps wouldn’t matter as much.

Of course, this difference was nowhere near large enough to complain if someone else set thermostat off by 1F, but if it’s just you, why are you avoiding the odd numbers in the first place?

All things considered, I’ll score this as a mild win. One cheer for Fahrenheit, I say.

1 comment:

  1. A friend of mine defended Fahrenheit by pointing out it is scaled for human perception in the Earth environment--0 is very cold, 100 is very hot.