* The linkage of length and mass standards, and the concept of using water to come up with a standard of mass, was first put forward by the same John Wilkins who suggested using a pendulum for length determination.
* One fewer after an accident in mid-May 2010 when the original Foucault’s pendulum of 1851, housed in the Conservatoire for decades, crashed to the floor, irreparably damaging its bob. The cable had snapped; some said that attendees at private parties held in the museum were known to have played with the solemnly swinging pendulum, weakening its stays.
* After serving as the U.S. standard for the meter for seventy-one years—and being taken to Paris four times during that period, for comparison with Le Grand K—No. 27 was retired in 1960 and sits in a glass case in a museum at the National Institute of Standards and Technology in Gaithersburg, Maryland, outside Washington, DC.
† China would not be a party to the treaty until 1977—by which time, as we shall see, the entire system of measurement had changed.
* The unstable isotope krypton-85, which has a half-life of eleven years, is a byproduct of nuclear explosions and fuel reprocessing—and the presence of plumes of the gas in the upper atmosphere has been detected by satellites orbiting over North Korea.
* Quite reasonably there is little that passes for poetry in any of the definitions, though maybe some will spy a hint of romance in the kelvin, which is defined as 1/273.16th of the temperature of the triple point—when liquid, solid, and vapor all coexist—of water. But not just any old water: the definition requires the use of what is known as Vienna Standard Mean Ocean Water, a cocktail of various distilled waters drawn from all the oceans—and yet perversely named for the capital city of a landlocked country about as far from the sea as it is possible for any part of Europe to be.
* As mentioned before, the seven fundamental units are the kilogram (of mass); the meter (of length); the second (of time); the ampere (of electrical current); the kelvin (of temperature); the candela (of luminous intensity); and the mole (of molecular amount). There are a range of what are called “derived units” to supplement these—such as the coulomb (electrical charge); the newton (force); the pascal (pressure); the farad (electrical capacitance); and some fifteen more, including the popular tesla, which, though defining an obscure property called the “magnetic flux density,” memorializes one of science’s most popular recent scientists, Nikola Tesla. He won this honor in 1960, seventeen years after his death.
* The sixty-second minute, the sixty-minute hour, and the twenty-four-hour day may now be near-universally accepted, but France has a long tradition of preferring decimal time, which supporters insist is logically connected to the decimal divisions of length and mass. For many centuries China divided its days in decimal fashion, but did so somewhat capriciously—there were extended periods of Chinese history when the basic unit, the ke, differed markedly in its duration from other periods. In the seventeenth century, the Jesuits brought harmony to Chinese timekeeping, declared the ke to be a quarter of an hour, and thence gently shepherded China into diurnal conformity with the rest of the world.
* The USNO was built on a low hill near the British embassy on Massachusetts Avenue, the site chosen to avoid light pollution from the then-small city to its south. Now it is surrounded by suburbs and a consequent vast amount of emitted light—and also as it happens by regiments of Secret Service guards, there to protect the onetime Superintendent’s Mansion, now the official residence (with a nuclear-hardened bunker beneath) of the American vice president.
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