Wednesday, July 21, 2010

In defense of Fahrenheit

We have weird measurements in the United States. 1760 yards to a mile, 3 feet to a yard, 12 inches to a foot; 16 ounces to a pound; 4 quarts to a gallon, 2 pints to a quart, 16 fluid ounces to a pint. They're ludicrously hard to convert, and I know nothing about a "pint" except that it's a measurement of beer.

Amid all this mess, people often criticize Fahrenheit. Granted, Fahrenheit seems less "natural" to people accustomed to powers of ten; why set freezing at 32 and boiling at 212 when you can use 0 and 100 instead? But there's really no practical disadvantage, because we never need to do arithmetic with temperature. Miles, yards, feet, and inches are annoying because they're a pain to convert, and they don't cleanly match up with our volume units in the way that a cubic meter translates to 1000 liters. None of these concerns are relevant for temperatures—we don't convert them, and we don't add them together.

In the end, judging whether Fahrenheit or Celsius is superior is really just a matter of convention and taste. While Celsius is slightly easier to remember, I don't think that recalling two short numbers poses too much of a challenge. Indeed, Fahrenheit has the advantage of matching up better with the temperatures we encounter outside: the range from 0 to 100 degrees Fahrenheit roughly corresponds to the most common temperatures on Earth, while temperatures above 50 degrees Celsius almost never happen.

So... absolutely, abolish the mile and retire the gallon. I welcome our metric overlords. But don't touch Fahrenheit—it's just as good as any other scale.


Shane said...

Fahrenheit is the worst of the offenders among standard-in-the-US-but-not-anywhere-else units.

Let's look at the history. Instead of just mixing ice and water to test the frigorific mixture's equilibrium temperature, Fahrenheit arbitrarily decided to add a bunch of salt (ammonium chloride, not even the most common salt available) to establish the zero point.

In terms of precision in describing comfortable ambient temperatures, no scale is really better than another - but that is no reason to not abandon Fahrenheit. It's simply better for applications where calories are a convenient unit, which should alone be sufficient to be the tiebreaker between two systems. Throw in the network effects and advantages of standardization that come with everyone else in the world using Celsius, and it's an easy choice.

Matt Rognlie said...

Granted, Fahrenheit is the most visibly arbitrary scale we have -- Fahrenheit seems to have been a bit of a bozo in setting the two endpoints. I just don't see why there is any compelling need to have freezing and boiling correspond to nice round numbers

The much more natural definition of the calorie under the metric system is a good point, but I can't imagine this being too important in practical terms. I find myself using most metric conversions at least once in a while -- I'll visualize a milliliter as a cubic centimeter, or a kilogram as roughly the mass of a liter of water. I can't see any day-to-day situation where I would need to think of a calorie as the amount of heat necessary to make a gram of water 1 degree warmer. Would anyone other than engineers or scientists ever need to do this conversion? (And it seems that they should be doing more exact computations on a computer anyway, since this conversion is only approximate and the true ratio varies nonlinearly depending on the starting temperature...)

Robbie Clarken said...

Celcius does have the advantage that converting to and from Kelvin just requires adding/subtracting ~237 which is a lot easier to do in your head than multiplying by some fraction. But your right... for nonscientists there is not much difference between C and F.

Robbie Clarken said...

Whoops... Obviously I meant 273 there!

John Blanchard said...

As a scientist, comparing ambient temperatures with cryogenic temperatures tends to get confusing because we use different scales with different regimes. Sure, not everyone's a scientist, but when measurements go from scientist to engineer to business to consumer, things have a way of getting mixed up (insert high school science teacher story about comically expensive NASA arithmetic mistakes).

Kevin Lee said...

When looking at it in the perspective of average human beings, the Fahrenheit scale makes much more sense. Water freezes at 32 degrees, and anything below that is unbearably cold. Water boils at 212 degrees, so a person must assume that because it is such a high number that living in those conditions would be void, but what does that matter to the average person? People only care when temperature are preferable and comfortable, so it is understandable that most temperatures around boiling point are irrelevant. A change in 1 degree Fahrenheit can be felt and can cause a minor disturbance, but a change of 1 degree in Celsius could prove deadly.
When compared to the Celsius scale, 0-100 becomes asinine to the average populace who are living normal lives. 0 degrees freezes and anything lower than that is cold, water boils at 100, but the range of that scale is extremely skewed. From temperatures above 45 degrees life seems to be challenged. While the same can be said about Fahrenheit with temperatures above 100+, the scale between 32 and 212, and 0 and 100 makes much more sense in the perspective of the human race.
In respect of the scientific community, it is understandable that because of studies relating not only to life terrestrial on Earth, but of chemicals and life from alien habitats, it makes sense to compare those things to the ranges of water as water is widely accepted to contain life.

Anonymous said...

Does 52 or 54 degrees Fahrenheit matter? I mean it's an unnoticeable difference. 32 or 34 degrees Celsius is a bigger difference and it matters. It's like saying 32,6 degrees Celsius. That ,6 doesn't matter, right? Who needs such a detailed scale?

The same goes for pounds. Why do you need such a detailed scale? Let's say you weigh 173 pounds. That's about 78,47 kg, So, you weigh 78 kg. You don't really need that ,47 again. That's really what bothers me about the imperial system.

Anonymous said...

How about calling football a game that is mainly played by hands?