2004 November 7
Bruce Alan Martin gives his story of "why SI has not quite caught on
everywhere" in 31414 of 2004 November 7.
For his number 5 there is another measure to use. Speed for cars is most
useful if shown in kilometres per minute. Airplanes use ETA, found from
minutes
to arrival. So minutes is the time number to use. For car travel, when you
know it is 50 km to Denver, and you drive 1.7 km/min, it is easy to see it will
take between 25 and 50 minutes to get there. You can divide and get 29
minutes. Now most of us do not divide distance by speed when we drive. We say
30
miles to Denver at 60 mph will take half an hour. The same accuracy is equally
easy with km/min. We should post speed limits in km/min.
In number 2, he is wrong. I just had to figure flight from New York to
Johannesburg. Well, on the globe it is 127 degrees. At 10,000 km per 90
degrees,
that is 14,100 km. Airplanes fly 1000 km/h so it takes 14 hours to get there.
Easy.
In number 3, the "fundamental unit of grams per meter cubed" is not the unit.
We use kilogram per cubic metre. This is an easy size. For millilitre
volumes we use grams, likewise easy.
He says bad choices will "prevent universal adoption". Wrong. Only the US is
left to adopt SI. The world has only 5% to go. And the US is already half
way there.
Robert Bushnell PhD PE
