Historic Vote to Redefine the Kilogram Changes Forever the Way We Measure Mass

Society | November 17, 2018, Saturday // 14:05|  views

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Talk about massive change. After meeting the needs of science, industry and commerce for more than 130 years, the kilogram has just been fundamentally reinvented.

At a meeting Friday in Versailles, France, representatives from the U.S. and 59 other nations adopted a resolution to define the familiar unit of mass in terms of the Planck constant, an unvarying and infinitesimal number at the heart of quantum physics.

 
 "Celebrations and standing ovation as the vote is accepted," the Bureau of Weights and Standards, which hosted the event where the vote was taken, said in a tweet featuring a photo of packed auditorium. "This has been a measurement revolution!"

Previously, the kilogram was defined as the mass of a specific physical object: a shiny metal cylinder that since 1889 has been stored in a vault on the outskirts of Paris. Cast of a platinum-iridium alloy and roughly the size of a votive candle, the International Prototype of the Kilogram (sometimes called "Le Grand K"), represents the mass of one liter of pure water at its freezing point.

The resolution will take effect on May 20, 2019.

The kilogram — which was and still is roughly equivalent to 2.2 pounds — was redefined in order to streamline scientific research and development involving ultra-precise measurements of mass. It aims to do that by ending the reliance on Le Grand K and official copies of it held by the U.S. and other nations.

 These reference kilograms, which periodically are taken from their protective cocoons for measurement and recalibration, are vulnerable to damage, wear and theft despite the care taken to safeguard them — and their masses have shifted by tiny amounts over the years.

"The change brings our best scientific understanding of the natural world directly into our daily lives, and gives us access to a definition of the mass unit which is available to everyone with the will and the skill to perform the experiments," Canada's chief metrologist, Alan Steele, told NBC News MACH in an email in advance of the vote.

In everyday life, the redefinition is expected to have no immediate consequence.

Source: NBC News


Tags: science, industry, measure mass, kilogram, changes, historic

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