Philanthropic pedantry

Perhaps this title is a little unfair, but it’s a pretty accurate way of describing the work of the International Committee for Weights and Measures (BIPM*). They put it like this however:

The intergovernmental organization through which Member States act together on matters related to measurement science and measurement standards.

I first heard of the organisation while watching a BBC programme about the kilo, based on the news that the original kilo is losing weight. That led me to discover the awesomely accurate BIPM definitions of weights and measures, such as this one I came across today for ‘the second’. Before the official definition, here’s their preamble to the history of the second, and their process of deciding how best to define it:

The unit of time, the second, was at one time considered to be the fraction 1/86 400 of the mean solar day. The exact definition of “mean solar day” was left to the astronomers. However measurements showed that irregularities in the rotation of the Earth made this an unsatisfactory definition. In order to define the unit of time more precisely, the 11th CGPM (1960, Resolution 9; CR, 86) adopted a definition given by the International Astronomical Union based on the tropical year 1900. Experimental work, however, had already shown that an atomic standard of time, based on a transition between two energy levels of an atom or a molecule, could be realized and The symbol, c0 (or sometimes simply c), is the conventional symbol for the speed of light in vacuum. The symbol, m (K ), is used to denote the mass of the international prototype of the kilogram, K.. reproduced much more accurately. Considering that a very precise definition of the unit of time is indispensable for science and technology, the 13th CGPM (1967/68, Resolution 1; CR, 103 and Metrologia, 1968, 4, 43) replaced the definition of the second by the following… (via The International System of Units (SI brochure (EN)): 8th edition, 2006)

So, if you still thought that a second was a fraction of a day, you are sorely out of touch! I just love the language and clarity here, and how much detail and consideration is communicated in just this one (albeit large) paragraph. Anyway, to the official definition of the second:

The second is the duration of 9192631770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom.

Be honest, how much of that definition do you properly understand, beyond the idea that it means ‘the time it takes something to happen to an atom’? More straight forward, though equally precise, obviously, is the definition of the meter”

The metre is the length of the path travelled by light in vacuum during a time interval of 1/299 792 458 of a second.

Which is interestingly reliant on the definition of the second. Anyway, great stuff. imagine if we could be as precise in other areas of life, like language, law, or etiquette.

* BIPM stands for Bureau International des Poids et Mesures, which reminds me how odd it is for an English speaker to come across acronyms that aren’t based on originally English names. The UCI (International Cycling Union) is another that always gets me. I wonder if such dyslexic seeming acronyms based on English are as disjointing for other languages, given the international use of English.