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A Newly Defined Kilogram Will Bring More Accurate Measurements To Kansas

Kansas Division of Weights and Measures
Stainless steel weights at the Kansas Metrology lab in Topeka, Kansass

The international definition of a kilogram has changed, and that could have implications for your next trip to the grocery store.

Until recently, the kilogram was an actual object: a hunk of metal sitting in a vault outside of Paris.

"There is only one kilogram in the world, and that's the one in France," said David Musick, director of the Kansas Division of Weights and Measurements.

All other kilograms, including a copy in Topeka, are just approximations that trace their mass back to the original. Copies of that copy are then used to calibrate scales across the state, from the one at your grocery store checkout stand, to those that weigh trucks on the highway.

But, like a game of telephone, the further away a copy gets from the original, the more likely it doesn't match.

Rather than rely on a more than 100-year-old piece of metal that's changing, the new definitionof a kilogram is based on how much energy it takes to balance a weight, a number that is measured using a universal constant.

"So now we'll be able to make a kilogram and say it is a kilogram," Musick said, "instead of it is a kilogram plus or minus 20 micrograms."

While that will help shorten the distance between copies and originals, the increase in accuracy will be so small that most consumers won’t notice a difference.

“In the future, when you buy a pound of bananas, it should be a little closer to an exact pound than maybe what it is today,” he said.

Even if only by a few micrograms. 

Brian Grimmett, based at KMUW in Wichita, is a reporter for the Kansas News Service, a statewide collaboration between KMUW, Kansas Public Radio, KCUR and High Plains Public Radio covering health, education and politics. Follow him on Twitter @briangrimmett.

Kansas News Service stories and photos may be republished at no cost with proper attribution and a link back to the original post.


Brian Grimmett is a two-time Regional Edward R. Murrow award-winning journalist covering energy and environment stories across the state of Kansas.