Scientists are about to redefine how much a kilogram weighs

CNET | 11/14/2018 | Jackson Ryan
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Weight is important. My burgeoning, post-holiday waistline gives me enough evidence of that, but that's not enough for science.

On Nov. 16, the General Conference on Weights and Measures -- which, look, I'm going to admit doesn't sound like the most riveting event -- begins in France. It's expected that at the conference, scientists will vote to change the definition of a kilogram, affixing it to one of the universe's immutable phenomena: The Planck constant.

Confusing - Let - Steps

That all sounds a little confusing, so let's take a few steps back.

The most widely used form of measurement in the world is based on the metric system, and is officially known as the International System of Units (SI). Seven "base units" make these up, including the ampere, the second and the mole. Some of those measurements were once defined by physical phenomena, such as the second, which was based on the Earth's rotation. Now, the second is defined by periods of radiation in a caesium 133 atom.

Kilogram - Base - Unit - Object

The kilogram is the last base unit linked to a physical object.

That physical object is a chunk of metal perpetually housed underground at the "Bureau international des poids et mesures", the International Bureau of Weights and Measures, in Sèvres, France. The platinum-iridium alloy, also known formally as the International Prototype Kilogram and informally as Le Grand K, is sort of like the ring in Lord of the Rings -- it's the one weight to rule them all. Every weight is calibrated against Le Grand K, standardising the measurement of a kilogram across the globe.

Le - Grand - K - Micrograms - Years

But Le Grand K, forged in 1889, has lost 50 micrograms in the last 129 years. The kilogram has become the "999.99995-gram." Except, even though it's lost that tiny fraction of its mass, the kilogram is still defined by Le Grand K, changing over time --...
(Excerpt) Read more at: CNET
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