Wednesday, October 03, 2007

About the size of it

I've just read "About the size of it" by Warwick Cairns.

I found it in the science section of a bookshop, so I imagined it was going to be a bit cleverer than it was.

It was interesting to hear about all the units in different countries that are more or less a foot long or a pound in weight and how such measurements as shoe sizes, pints and train gauges evolved. I was previously unaware of the fact that the traditional US and UK measures were the same until 1824 when the UK gallon was resized to correspond to 10 pounds of pure water (supposedly to make shipping cargoes easier to calculate) as opposed to 8 pounds of wine. This is why the (so-called) traditional British pint is bigger than its American counterpart.

His arguments for why such sizes make sense in everyday life are very compelling. However, the underlying anti-metric tone gets a bit silly.

Yes, the fundamental unit of time in SI units is the second - but that doesn't mean that you can't use minutes and hours, they are defined in terms of the second. Yes, the base unit for length is the metre and there is no separate base unit for volume (because you can express volume as cubic metres) but no, that doesn't mean that you have to buys drinks at the bar in cubic metres any more than someone ordering a regular cola in McDonald's has to specify the volume.

He completely ignores one of the key features of the metric system (especially in its modern SI units form), which is the simplicity with which measurements can be manipulated and expressed.

1) A lorry has a cargo of 5120 boxes each weighing 198.5g - how much does the cargo weigh? 5120 x 198.5 = 1,016,320g; now, simply by shifting the decimal point, I can easily convert it to kg or tonnes.

2) A lorry has a cargo of 5120 boxes each weighing 7 ounces - how much does the cargo weigh? 5120 x 7 = 35,840 ounces; erm, best divide that by 16 to get pounds: 2240 pounds; what's that in more convenient units? well, it's a British (long) ton or 1.12 American (short) tons. So even when the numbers are nice round figures and add up to a standard unit: it's still a big faff!

The argument that different sorts of human things lend themselves to different sizes is well made and valid: the weights or volumes of food we want to buy pretty much conform to traditional measures such as a pound or a pint - and are meaningful in a handy, human, everyday sense; but saying that this undermines the metric system doesn't make sense to me.

If you reject his assertion that using metric means that everything has to be in multiples of ten, then there isn't a problem e.g. wine in the EU is sold in 750 ml bottles, a perfectly appropriate size for a wine bottle and completely metric.

In an industrialised world, things are transported, manufactured or processed in bulk and, in a digital age, they are tracked, measured and accounted for using computers; these things are best handled using the metric system. This should not, in my opinion, preclude people from asking for a pound of bananas and being sold a pound of bananas, but the idea that people should continue to insist that they will only measure the things they sell in pounds is just silly. If a chemist insisted on measuring out medicines in grains, you'd go elsewhere.

...and while we're at it Metric Myths.

No comments: