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From May 2019, we will consult a natural constant to determine the kilos instead of the physical kilo in Paris
The Big K: the real physical kilo that serves as a criterion for all other kilograms on the globe. Or, because after nearly 130 years of service, the primitive kilogram will soon be exhausted. This was decided today, on the last day of the 26th e Congress of Metrologists of Versailles.
The decision was postponed four years ago, but everyone is now in agreement. The kilogram was the last major unit of measurement physically defined. From May, kilograms will also be based on a natural constant; The Planck constant. The blur should make it easier to reproduce the measurements.
Read also: Why and how our kilo is shoveled
Arrived
The kilo, officially international prototype of the kilogram is a platinum-iridium alloy block stored under three glass plates in a vault located in the cellar of the Office of Weights and Measures (BIPM) in Sèvres, near Paris. Since 1889, this kilogram of kilograms exists and, although controlled conditions and regular cleaning can prevent anything that could affect weight, the block has just arrived.
Constants of Nature
The last unit of measure that was still defined on the basis of a physical artifact, it was time to change. Just as, for example, the counter is determined according to the speed of light, the "new" kilogram will also be calculated using a constant natural. Specifically Planck's constant;
Instead of taking a trip to Paris and comparing physical pounds, the Kibble balance can soon be used. The expensive scale determines the weight on the basis of electricity, which can be translated into energy and thus returns to the Planck constant. But precisely by using the energy and Planck's constant – 6,62607015 x 10 -34 Joule – there are more ways to calculate the new "electric" kilos.
A historic change that will have consequences for measurements everywhere in the world. However, we will not notice much in everyday life, the difference is too small for that.
Sources: BIPM, phys.org, NRC
Image: BIMP
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