## More metric-imperial conversion hijinks

A while back I noted how an article on Ebola in the NY Times had apparently translated “one millilitre of blood” in a medical context into “one-fifth of a teaspoon of blood”. Hilarity ensued. Now I see that the fun doesn’t go in only one direction. I just got a letter from the NHS about an upcoming appointment, including these instructions:

Do not come to your appointment if you or anyone living with you has the symptoms of a new continuous cough (in the last week) or a temperature above 37.8 degrees or loss or change to your sense of smell or taste.

37.8 degrees? Why exactly this number? It sounds both arbitrary and absurdly precise. A bit of reflection revealed that 37.8 degrees Celsius is precisely 100 degrees Fahrenheit. They obviously copied some American guidelines, and instead of rounding appropriately — or reconsidering the chosen level — they just calculated the corresponding Celsius temperature. The funny thing is, Americans are used to having the very non-round guideline of 98.6 degrees as the supposed “normal” body temperature, because someone* in the 19th Century decided 37 degrees Celsius was roughly the right number, and that magic number got translated precisely into Fahrenheit.

* Carl Reinhold August Wunderlich, actually.

## In the still of the night

I just read a popular book on chemical elements, The Disappearing Spoon by Sam Kean. It was very entertaining, and seemed quite credible and clear, even if slightly fuzzy on the quantum mechanics. There was one claim that I took exception to, though:

The length of a day is slowly increasing because of the sloshing of ocean tides, which drag and slow earth’s rotation. To correct for this, metrologists slip in a “leap second” about every third year, usually when no one’s paying attention, at midnight on December 31.

Is there any time in the year when people are paying more attention to the time exact to a second than precisely at midnight on December 31? Does he think people would notice an extra second if it were interpolated at noon on July 7? I always assumed they did it at the one time of year when people would notice an extra second precisely because they want to be noticed. “Never fear, humble citizens. While you sleep, we are looking after your time.”

## Metric overlap

I was just reading this article about the failure of the US to convert to the metric system in the 1970s — a review of the book Whatever Happened to the Metric System? by John Bemelmans Marciano. (About whose title I wonder, whatever happened to the phrase “what ever”? Isn’t “whatever” a completely different word? Whatever.)

It reminded me of my school days, when the units unit — the unit on converting between English and SI units — was a regular feature of every year’s math lessons. We were told that this would be important for the future, since everything was going to be converted to metric. Something to justify a lifetime of skepticism toward those

At the time, I thought it strange that so much time was being spent on converting between the old and the new units. Once you start using new units, you rarely need to convert to the old ones; and most of the conversion can be done with double-marked measuring utensils, like the measuring tapes that were then and still are ubiquitous. (I was fascinated when I first saw the 18th century clock faces that have the hours subdivided simultaneously into fours and into fives, the latter to accommodate the new-fangled minute hands, the former for the old one-handed system, where a single hand showed the time on a 12-hour or 24-hour scale (or 10-hour, if it was late 18th century Paris), with each hour subdivided into quarter hours. An example, from a much later date (mid-19th century, pictured above) is the face of Big Ben in London.

Emphasising conversions made it seem like metric requires hard math, as well as remembering things like 3.28 feet in a metre, or 454 grams in a pound, whereas it actually means you can stop remembering things like 5280 feet in a mile, or 4840 square feet in an acre, or 4 pecks in a bushel. But I remember being particularly struck at the time (the time being about 1980) by an argument I read, claiming that metric conversion would impose untold costs on the US economy, requiring the replacement of everything from shot glasses to wrenches. I found this claim very odd. Surely, I thought, the fact that we measure the size of drinks in millilitres rather than ounces doesn’t forbid us from making a drink have an odd number of millilitres, at least until the old glasses break.

It reminds me of when Deutsche Telekom, in the pre-competition days, proposed changing the basic unit of charging for local calls from three minutes to half a minute, or maybe it was even less. I remember listening to a call-in show on the radio where this was being discussed, and an elderly woman called to express her outrage. “Who would make a half-minute call? What can you discuss in so little time?”

Anyway, metric didn’t happen in the US, except for the 2-litre pop bottles, and gram bags of cocaine. But even where it did happen there remains an overlap of older units. In Britain, which has been metricated by law since EEC accession in the 1970s, house sizes are in square metres, petrol sold by the litre, and fruits are priced in pence per kilo, but beer is sold by the pint and distances between cities are generally measured in miles. People’s weights seem to be given equally in pounds, kilos, or stones (14 pounds). Commonly imperial units are given as alternatives to officially required metric units, suggesting that at least some portion of the public has a better intuitive grasp of the imperial units. But even in Germany, which had the metric system imposed by Napoleon more than 2 centuries ago, people still talk of “Ein Pfund Butter”, even if this “pound” of butter is a metricated pound, rounded to 500 grams.