Number of words – 293

The metric unit of energy is the joule. It’s named after James Joule, with the symbol J. Although the names of all units are written in lower case letters, their symbols are capitalized when they’re derived from the name of a person: so the newton of force is symbolized N.

This principle caused some interesting confusion a few years ago over the litre. The metric commission prefers to use a lower case script L for the symbol; but since that would cause some typographical difficulties, they allowed L also to be used. (they couldn’t use l, because it’s too hard to distinguish from 1.) But that makes it looks as if the litre is named for a person. So a physicist at the University of Waterloo invented a Sieur de Liter, an obscure French chemist of the eighteenth century, and published his brief biography in the April issue of a newsletter for chemistry teachers. Though he’s had some fun with it, he sometimes wishes he hadn’t.

I think the physicist may have been encouraged by how the Celsius scale got its name. For many years it had been the centigrade scale, but using C for its symbol. At some stage in metric deliberations, someone said, we could keep the capital C and follow our new rules for symbols if we could find someone to name this scale after. Searching into the history of thermometry, they found a name beginning with C, Anders Celsius, a Swedish astronomer. He’d even suggested dividing the range between the freezing and boiling temperatures of water into 100 parts. But, for some obscure reason he put zero for the boiling point and 100 for freezing.           

Excerpted from ‘Children of Promotheus: A history of Science and Technology’ by James McLachlan