The weights and measures system has a problem. The kilo is not what it used to be
Since 1889 the kilogram has been defined as the weight of a cylinder of metal kept under guard at the International Bureau of Weights and Measures in Paris. To the bafflement of scientists they have discovered it's weight is changing. Measurements confirm it's mass has changed by about 50 microgrammes - the equivalent of a tiny grain of sand - over the last 100 years. "Actually, we're not sure whether it has lost mass or gained it," said Alain Picard, director of the Bureau. "The change may be to due to surface effects, loss of gas from the metal or a build-up of contaminant".
This is particularly irritating to the French authorities as the 99% platinum/10% iridium cylinder was made in Britain and is the 'base constant' of the metric weights and measures system. The International System of Units (SI) depends upon it remaining constant to provide a precise measurement standard for engineers, scientists and merchants. If a kilo of spuds is no longer the same as a kilo of spuds a hundred years ago that is an oddity, but if a kilo of diamonds in Paris is now different to a kilo of diamonds in Africa then that is a problem.
This opens up the possibilities for some good arguments with your local Trading Standards department: "Don't blame me - my scales are calibrated against the French" etc. but it's also a reminder to have your scales recalibrated and PAT-tested from time to time. Your supplier will do this for you at modest cost.
Unlike its six 'base unit' standards in the SI system - the metre, second, ampere, kelvin, mole and candela - from which all other measurements are derived the kilo is the last unit still defined by a physical object. It will now go the same way as the platinum ruler which used to represent the world's standard metre. That was replaced by a 'fundamental constant' - the time light takes to travel 100 centimetres. The kilo will now become a fixed value of the 'Planck Constant' which in turn corresponds to the smallest packet of energy two particles can exchange.
What a shame - I like to see something for my money, not some weird mathematics devised by scientists. The platinum ruler and standard kilo will be placed on display in Paris, but only as historical curiosities. They have gone the same way as the purpose-built weigh house which often remains the most impressive building on a market square. Grainger Market, Newcastle contains a fine weigh house which used to house the weights and measures officers and measuring equipment.
Surveyors quickly learn that measurement is not an exact science - it depends on the accuracy of your technique and the precision of your tape measure. Ask a Surveyor, a Stallholder and the District Valuer to measure the floor area of a stall and you'll be lucky if their figures agree to within 5%. This causes all sorts of fun when calculating rents, rates and service charges by floor area and I can think of one case when I realised the District Valuer had forgotten to include the entire basement in his business rates calculations. Needless to say his proposal was accepted very quickly and he either never realised his mistake or was too embarrassed to admit it. A good result.
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