GIGO

Metric Musings

Vicki Hyde

Give him 0.3048m and he'll take 1.60934km. OK, so there are some things which just don't translate well into metric, but one would have hoped that NASA, of all organisations, would have recognised the dangers of changing between units.

Keen Mars-watchers were dismayed to hear that the Climate Orbiter mission somehow splattered itself on the Red Planet, but it was much more dismaying to hear that the loss was due to one engineering team using metrics and another using Imperial units. When your tolerances are critical, even something as apparently harmless as rounding off conversion factors to two or three decimal places can be disastrous.

Unlike the United States, New Zealand has, for the most part, become fully metricated. We may still revert to Imperial measures for the odd specialist subject ("a 4 kilo baby, what's that in pounds?"), but we got there officially in under 10 years. And we're generally sensible enough to recognise when conversions aren't necessarily appropriate -- does anyone really measure a cupful down to the last gram, or worry if their cake tin is not precisely 254mm (10 inches) in diameter??

To add extra spice to the problem, metrics have always had a political component to them, starting with their revolutionary (in more ways than one) origin. And there certainly remains a good deal of politicking in the farcical on again-off again attempts by the US to metricate.

Interestingly, though a great deal of attention has focused on the calender system this year, complete with comments about how England and Russia came so late to the Gregorian calendar, virtually no attention has been paid to the comparable shambles of a shared measuring system. We think of science being international, and science accepting the SI units (Systme International d'Units) -- one would have hoped that engineers would be part of that confraternity.

It's not just spacecraft which have problems. A friend recently came back from wintering over in Antarctica. He landed in Christchurch to be told it was 38^o outside. Sadly the shorts he optimistically brought with him didn't do much for him in the teeth of a bitterly cold southerly...

Vicki Hyde is the editor of New Zealand Science Monthly.