platinum-iridium

Standard, against which all others of the same category are measured. Usage: silly. The notion is that one of whatever it is has actually been cast in platinum-iridium alloy and placed in the vault beside the Standard Kilogram at the International Bureau of Weights and Measures near Paris. (From 1889 to 1960, the meter was defined to be the distance between two scratches in a platinum-iridium bar kept in that same vault -- this replaced an earlier definition as 10^-7 times the distance between the North Pole and the Equator along a meridian through Paris; unfortunately, this had been based on an inexact value of the circumference of the Earth. From 1960 to 1984 it was defined to be 1650763.73 wavelengths of the orange-red line of krypton-86 propagating in a vacuum. It is now defined as the length of the path traveled by light in a vacuum in the time interval of 1/299,792,458 of a second. The kilogram is now the only unit of measure officially defined in terms of a unique artifact. But this will have to change; in 2003 it was revealed that the reference kilogram has been shedding mass over time, and is down by 50 micrograms.) "This garbage-collection algorithm has been tested against the platinum-iridium cons cell in Paris." Compare {golden}.

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