The Unfulfilled Potential of the Metric System

Australians are fond of dunking on Americans for not using the metric system, but the conversion to metric happened in 1970 and obviously hasn't been complete. Speech here is filled with Imperial units -- inches, gallons, miles -- even among younger people who were born after the adoption of the metric system. People routinely give their heights in feet and inches and the weights of their new infants in pounds and ounces. Temperature is the only thing I would say is truly always measured in the metric system.

I'm gaining an intuitive grasp of the temperature in Celsius degrees, and getting better at expressing speeds and distances using kilometers. But I miss having a unit to describe a length of about a foot. It seems like a good length to have shorthand for.

My biggest problem with metric, though, is that its biggest claim to usefulness is the easy conversion among units. It turns out this is not all that easy for people practicing it. Publications are riddled with conversion mistakes. For example, I recently read an article about a person whose height was mistakenly given as 1.25 cm instead of 1.25 m.

Even more than little errors of conversion or expression of units, though, is that users of the metric system don't take full advantage (in speech, at least) of the idea that you can express quantities in any power-of-ten of the base units. People describe long distances in thousands of kilometers, and never convert to megameters. An Olympic swimming pool's volume might be expressed as 2.5 million liters, not 2.5 megaliters. An astronomical unit, defined as the distance between the Earth and our sun, is about 1.5 x 10^11 meters. You could also say it's 0.15 terameters or 150 gigameters, but no one ever does.

The reason is probably that it's not intuitive. Metric users never complain about the idea of a minute, though our common measures of time are not remotely based on powers of ten. This is because whatever units you grow up using become intuitive to you before you even have any concept for how and why things are measured. And that's the interesting thing. People who grew up using metric units frequently ask me how the hell kids learn how warm a Fahrenheit temperature is or how far a mile is. These measures are exactly as intuitive as understanding a Celsius degree or a kilometer for the first 15 or so years of life, until you have to start doing math about it. The metric system makes math easier, but it doesn't have that much bearing on how most people live day-to-day.

This isn't an argument against the metric system. Let's relegate yards to the game of football where they belong.