Published: Sun, November 18, 2018
Global Media | By Garry Long

Scientists vote to redefine the kilogram in France

Scientists vote to redefine the kilogram in France

Now, after a week-long meeting at the Palace of Versailles representatives of 60 nations agreed to redefine the kilogram based on the unchanging value of the 'Planck constant'. This will assure the future stability of the SI and open the opportunity for the use of new technologies, including quantum technologies, to implement the definitions.

"This is the most important decision that the BIPM has made in maybe 100 years, which may be a slight exaggeration, but at least since 1960 when they adopted the International System of Units", Terry Quinn, emeritus director of the BIPM, told Engadget last year. Save for a few archaic holdouts who still measure things by sheep intestines and cow brains, the entire world has standardized on this system, so that regardless of where you are, things innately make sense. It is now being retired and replaced by a new definition based on a scientific formula.

The ampere is now being defined from the elementary electrical charge, (e), the Kelvin is defined from the Boltzmann constant (k).

But the master copy, known as "Le Grand K", has been picking up microparticles of dust, or losing mass in cleaning, causing consternation for scientists using it to measure ever more accurate weights. In fact, what the science community has done is define Planck's constant as a specific value: h = 6.62607015 × 10 J∙s.

For nearly 130 years, the fundamental unit of weight has been set by a cylindrical chunk of metal housed under a glass dome at the International Bureau of Weights and Measures (BIPM) near Paris, France.

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A kilogramme since 1889 has been defined as the mass of a cylinder of platinum-iridium alloy known as the International Prototype of the Kilogram and nicknamed "Le Grand K".

Barry Inglis, Director of the International Committee for Weights and Measures said, "Today marks the culmination of decades of work by measurement scientists around the world, the significance of which is huge". The new definitions will be effective on May 20, 2019, World Metrology Day, which celebrates the establishment of the SI, or metric system, in 1875.

It is expected to be more accurate when measuring very, very small or very, very large masses and help usher in new innovations in science, industry, climate study and other fields. He said, "We will now no longer be bound by the limitations of objects in our measurement if the world but have universally accessible units that can pave the way to even greater accuracy and even accelerate scientific advancement", he said. "We can now measure everything more accurately using knowledge of how the universe operates at the atomic level than we can using objects we can can see and feel".

Quantum phenomena that are identical everywhere are already used to define the second, which is the SI unit for time, and the meter, the SI unit for distance. It is also created to facilitate today's constant technical innovations.

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