The new unit of (radio)activity, and a very inept one. The becquerel (Bq) equals 1 disintegration per second and equals 2.7 x 10^-11 curies. Unlike the gray (=100 rad) and the sievert (=100 rem), which are merely unfamiliar, but jibe with the other units of the metric system, the Bq violates a principle that well-bred units respect: the size of a unit should be appropriate for the field in which it is used. For example, the "household" units such as the foot, meter, pound, meter or gallon do not usually occur in thousands or millions around the home or at the supermarket. Where the meter is too small
¾in astronomy, for example¾it is replaced by bigger units, such as the AU or the light year; where it is too large¾in optics, for example -it is replaced by a smaller unit such as the angstrom (1/10,000,000 of a meter). It would be inept, though roughly true, to say that I am 18,100,000 angstroms tall.Yet that is exactly what the becquerel does. Not only is it too small for scientific fields such as health physics, but in the days after Chernobyl, people were needlessly frightened by the announcements of thousands and billions of becquerels
¾just like many might have imagined that a man 18,100,000 angstroms tall must be a giant reaching halfway to the moon.The old and familiar unit of activity, the curie, is defined as the activity of one gram of radium. A gram of radium knows nothing about the metric system and fires away with 3.7 x 10^10 disintegrations a second (and just as many becquerels, which determines the conversion). But a gram of radium is also in the ball park of what health and other physicists usually deal with.
There are other units that violate this rule of good breeding. Clearly the kilogram is a unit derived from the gram, which is 1,000 times too small to be of any use at the grocer's; and there are other scientific misfits (the decibel is 0.1 of a bel, and both the farad and the coulomb are way too large). But the reasons are historic, and it is impolite to point to the bad manners of venerable old men. The Bq, to the contrary, was made official but a few years ago; it is not yet a teenager and already an ill-behaved nuisance.
None of which, of course, reflects on Antoine Henri Becquerel (1852-1908), professor at the Ecole polytechnique in Paris, one of the world's great engineering schools. He discovered radioactivity in 1896, and in 1903 shared the Nobel Prize with Pierre and Marie Curie, discoverers of the element radium.
|
|
Vol. 14, No. 2
Newsletter: Access to Energy Newsletter Archive Volume: Issues Issue/No.: Vol. 14, No. 2 Date: November 29, 2004 04:54 PM Title: Justice and St. Karen
Copyright © 2004 - Access to Energy Newsletter Archive
|