This Kilogram Has A Weight-Loss Problem : NPR »

Posted By bruhaha 3 months, 3 weeks ago in Science & Technology

More than a century ago, a small metal cylinder was forged in London and sent to a leafy suburb of Paris. The cylinder was about the size of a salt shaker and made of an alloy of platinum and iridium, an advanced material at the time.

In Paris, scientists polished and weighed it carefully, until they determined that it was exactly one kilogram, around 2.2 pounds. Then, by international treaty, they declared it to be the international standard.

Since 1889, the year the Eiffel Tower opened, that cylinder has been the standard against which every other kilogram on the planet has been judged. But that's creating problems. According to scientists, the cylinder's mass appears to be changing.

The solution is a new kilogram, one that is based on a constant number instead of a physical object. To get that number, scientists have had to build a special kind of scale, one that measures the kilogram without balancing it against another mass. It has been a long, slow process, but today they are close to redefining the kilogram once and for all.

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Submitted By:
bruhaha

Geologist at an environmental consulting and engineering company here in the Chicago suburbs.

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