I just looked at the front page of Wikipedia: today is the anniversary of the loss in 1999 of NASA’s Mars Polar Lander. I thought that was the one that crashed through a mix-up of metric and non-metric units, but on checking it out I found I was mistaken. It was that spacecraft’s partner, the Mars Climate Orbiter, which had the metrication problem a couple of months previously. (MPL actually suffered a different problem caused by its human designers: when the landing legs clicked into place it created a vibration that the onboard software interpreted as touchdown and shut off the rocket motor. It was still high in the Martian skies.)
But hey, I’m not going to let exact anniversaries (or lack thereof) put me off my blog. I’m all for metrification. NASA and all other Federal agencies, plus the US Military, have been using metric units for over thirty years. Lockheed-Martin makes rockets in feet and inches though. Westinghouse designs nuclear reactors in feet and inches, causing extra work for the UK’s Health and Safety Executive when they evaluated proposals to build some in Britain. But it’s OK. HSE says the designs aren’t safe in any system of units.
When I was in Italy this year, I decided I needed to buy some new trousers, and went to an “outlet” warehouse selling discounted brands. I’m not proud. I was surprised to find that a lot of the garments were marked in inches, so I bought the same size as I would at home. That’s a 30-inch waist and 34-inch legs. Since I’ve really only used metric units when I measure things, I don’t really have a feel for what “30 inches” means, but you’re not really buying a measurement so much as an arbitrary size, so it doesn’t matter. In the same way, I’d know not to bother trying a jacket labelled “XXL”, (or a size 8 dress) even though there’s no exact definition of what it means.
But that kind of sloppiness isn’t good enough for the EU’s civil servants. Hence: EN 13402, a European standard for clothing measurements. In metric units, naturally. Apparently, it’s based on modern measurements of typical body shapes, whereas previous systems date from the 1950s and people were different then. (I think what that means is that the Western world is full of fat bastards now.) In EN 13402, each class of garment is assigned a “primary dimension” which must be labelled in centimetres. For example, a man’s jacket must show the chest measurement. One or two “secondary dimensions” can be added — for a jacket, they can be waist and height.
Naturally, like a typical schoolboy, I was drawn to the rude parts of the standard. And for bra sizes, they’ve kind of messed it up. Sticking to the system, there would have been one primary dimension and one secondary dimension, in their terminology “bust girth” and “underbust girth”, although which you defined as “primary” would not really matter. But, rather than requiring, say, a label to read something like 70 85, the standard goes back to the old idea of a letter code for cup size, by subtracting one from the other. A difference of 15 means “B” so that’s a 70B.
That ought to confuse the Americans.