How long is a foot? If you have a 12-inch ruler, how can you tell if it is actually and exactly 1 foot? What about a meter? And what about a cubit? And if you have 1 kilogram of something, where in the world is a standard by which your sample can be measured? And how long is an hour? (A lot shorter when making love than when sitting on a hot stove, as some wit once remarked.) Or the strength of a volt or an amp; or the brightness of a light? And so on.
“The Science of Measurement” tackles these questions in a three-part series from Athena Learning. Here Marcus du Sautoy very nicely explains the earliest attempts at answering these seemingly unanswerable questions, then he discusses more recent attempts, and finally he arrives at the attempts at establishing measuring standards by connecting them to unchanging forces of nature.
For example, a “span” used to be the distance from the tip of a person’s thumb to the tip of his little finger when the hand is spread out. Different size hand, different size span. Not good. Centuries later, a bar was created to be the standard meter and kept under the most controlled of all possible conditions. Very good but not perfect. Today, certain wave lengths of light are used. Since they never change—an assumption, come to think of it, but what can we do?—we have a perfect measure of the meter.
At times, the technology might be a bit too much for many viewers, but all in all this is a really outstanding educational DVD. (If only they would stop showing speeded up traffic flow to suggest—I guess—the progress of human thought. And, please, stop with “And things were never the same”!)
Each episode is just short of an hour and the subtitles are as always most helpful. So is the booklet that Athena always includes.
Addendum. I lent my copy to an engineer and he went nuts over it. Not only getting a copy for himself, he bought several for several of his colleagues. This is quite a recommendation.