I was recently traveling in Europe (including in Switzerland, where 87% of trains are less than 3 minutes late). While I was in Cambridge, England, my old friend and colleague David MacKay, who shares my antipathy to bad numbers, gave me a copy of a recent article in the UK journal Physics World (“Optoelectronics: a green explosion”, May 2011, p. 5 of the optics supplement). The article touted laser-based “green technologies,” including their use in reducing carbon-dioxide emissions:
Volvo’s Johnny Larson says it is possible to shave a few kilograms off the weight of a car’s metal frame by optimizing its design for a laser process. This has knocked up to 2 kg [4.4 lbs] off the XC60, and for every one of these models that clocks up 100,000 km [60,000 miles], 24 kg [53 lbs] of carbon-dioxide emissions will be saved.
So many numbers, so little meaning! Whenever I see so many numbers, I think of what Socrates might have said: “The uncompared number is not worth knowing.” Let’s start with the 2-kg weight reduction.