Earthlings have abandoned the weight standard.
May 20, 2019 - on World Metrology Day, a holiday that has been celebrated for 20 years since 1999 - humanity has abandoned the last remaining material standard. Namely, from a kilogram - a cylinder known to everyone from a school bench made of an alloy of iridium and platinum. From now on, he is a museum exhibit, and not an object with which everything significant must be compared. Will sink into oblivion and seemingly unshakable definition, which we learned by heart in physics lessons: " A kilogram is a unit of mass equal to the mass of the international prototype of a kilogram. " Forget it. Now the kilogram will be determined through the universal constant - Planck's constant. And with electricity.
The historic decision to "decouple" the kilogram from the material benchmark was made in 2018 at the General Conference on Weights and Measures in Paris. It was preceded by long thoughts and hard work. And it took another year for the decision to take effect. As it is written in it, "the kilogram will be such that Planck's constant is exactly 6.626069 x 10 to minus 34 degrees of the joule per second." Why is that? Because it was precisely with such accuracy that the Planck constant was measured. Several years ago, American physicists from the National Institute of Standards and Technology (NIST) did this by installing the NIST-4 watt balance - the so-called Kibble balance or watt balance, on which gravitational forces are balanced by electromagnetic ones. Now these and similar devices will "measure" the kilogram. Scientists assure that the accuracy of the scales is amazing - one that meets the requirements of the time, namely the need to sometimes weigh objects the size of a molecule or an atom, without depending on something material.
The most modern Kibble scales, with which they will now * measure * kilograms.
The basic diagram of the Kibble balance operation: the magnetic field generated by the current in the coil creates a force that balances the load.
Rejection of the standard will not affect everyday life.
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Promotional video:
The material standard for the kilogram is kept at the Bureau International des Poids et Mesures in Sevres, France, in a deep bunker. It is a cylinder made of an alloy containing 90 percent platinum and 10 percent iridium. The cylinder has the same height and diameter - 39.17 millimeters. It was made in 1889.
This is how the material standard of the kilogram looks like. Next to it is an inch ruler.
Many countries, including Russia, have copies of the standard. They are periodically compared - standard and copies. And they are surprised to notice that the copies get a little heavier - they add about 20 micrograms relative to the original in 20 years. The reason for the phenomenon is unclear. He was embarrassing. Such instability and resulting errors largely predetermined the fate of the precious rarity. Having “written off” the cylinder, specialists will continue to monitor it in order to record the changes taking place.
VLADIMIR LAGOVSKY