Categories: world

Tell Au Revoir to the metal hunter in France who has defined kilograms

Posted 11-13-2018 by Nell Greenfieldboyce BIPM Wrought in 1879 and sanctioned by the General Conference on Weights and Measures at…

Posted by Nell Greenfieldboyce


Wrought in 1879 and sanctioned by the General Conference on Weights and Measures at its first meeting, Le Grand K, the international prototype of kilot, has been held under locks and keys in a vault outside of Paris.

The world is about to say au revoir to Le Grand K, a cylinder of platinum and iridium long ruled over the world’s weight measurement system.

Le Grand K was erected in 1879 and held in a locked vault outside Paris – revered and held under lock and key because its mass, just over 2 pounds, is the official definition of the kilogram.

But this will soon change. On Friday, the International General Conference on Weights and Actions will meet in Versailles, France, to vote on whether the code should be redefined.

The voice is expected to be the only one, only formalism after many years of work. In the future, the world’s mass measurement system will not be based on any particular metal demand but rather on unchanging properties in the universe, such as the constant speed of light, time and planck.

“It’s amazing! It’s great! It’s history at work,” enthusiasts Zeina Kubarych at the National Institute of Standards and Technology in Maryland, specializing in measurement science.

“We are replacing a mass realization system we have had for 129 years,” she says. “It’s a big event.”

Kubarych works in a safe, climate-controlled lab on NIST that holds a pair of folded metal cylinders, each underneath – not one but old fashioned glass clock. The United States received these official duplicates of Le Grand K after signing the 1875 Meter.

“These are our national standard sources,” explains Kubarych. “That’s what we use as a basis for our mass media system in the United States.”

These ancient artifacts are very important for anyone who needs to make comparisons to make sure their exact measurements are not worrying. It includes state-of-the-art testing laboratories that test and certify the waves used in stores and pharmaceutical companies, for example, as well as scales used by aircraft manufacturers and manufacturers of scientific instruments.

“It broadly spans most of the US industry sectors,” said Kubarych.

The official kilograms of the nation are so valuable that “we are not touching them,” says Kubarych.

“We do not even try to touch them with hand screws.”

Instead, carefully pick up the metal items with a special tool wrapped in filter paper – to avoid leaving small scratches or fingerprints that can turn off the weight.

And it’s the big problem of basing a measurement system on the comparison of metal pieces. If Le Grand K becomes heavier or lighter – or absorbs atoms of something from the air – the definition of the kilogram changes literally.

Researchers think that something like this has happened, because Le Grand K seems to weigh slightly less than its Official Copies.

Perhaps any teeny fluctuation would not do anything for the average person who buys, says, coffee in weight at the supermarket. But scientists despair the idea of ​​trying to understand reality by means of constantly changing measurements.

Refining the kilometer means that researchers will “finish something that was probably begun before the French Revolution,” notes Stephan Schlamminger of NIST.

Behind Revolutionary Times, Enlightenment Hugs Hated the World’s Hodgepodge of Measurement Systems – each based on a random object, such as the length of a local deer’s foot. Their radical vision was to create something rational and general, says Schlamminger, and noted that the metric system would be “for all times, for all people.”

These metric-based authors based it on the globe, with the meter described as a 10 million distance from the north pole to the equator.

But for a long time, the meter was literally a metal bar in France.

As physics advanced, Schlamminger says, researchers could remove the metal rod and define the meter with respect to the distance that the light can travel through a vacuum for about 300 million seconds.

“And this,” says Schlamminger, “is the idea of ​​moving from an artifact to a fundamental constant. “

Now, after researchers used years to create a new type of weighing machine called a Kibble balance, it’s finally kilograms trip.

In the future, to see if a metal fool really weighs 1 kilo, needs It does not fly to France and is compared to Le Grand K. It can be evaluated in this type of instrument, using Planck’s constant.

Sch lammings and two of his colleagues are so devoted to redefining the kilogram as they recently received tattoos that show

NIST Jon Pratt, one of the tattooed scientists, says it was difficult to measure Planck’s constant, convinced that the world would switch to a new kilo based on it.

“There were plenty of committees and finesse and inhibition and cancellation on this, “says Pratt.” So we knew what we were for. We knew it would be painful. And we all agreed that we would get wet with the number when we made it. “

If the vote goes as expected, the new definition of the kilogram will come into force in May.

Meanwhile, Le Grand K will remain in its single vault.

” It is a historical artifact that has been studied for 140 years and will retain some metrological interest, “says his guardian, Bureau International des Poids et Mesures,” although its mass will no longer define the kilogram. “

Copyright 2018 NPR. To see more, visit
Published by