Jul 6, 2017 12:11 AM
https://www.washingtonpost.com/news/spea...s-massive/
EXCERPT: [...] Here's the problem with the current standard kilogram: It's losing weight. It now is ever-so-slightly lighter than the once-identical “witness” cylinders stored in labs around the world. Scientists don't know whether the BIPM prototype is losing mass, perhaps because of loss of impurities in the metals, or if the witnesses are gaining mass by accumulating contaminants.
Either way, the whole thing is a “huge inconvenience,” Pratt said. Several years ago, NIST had to reissue certificates for its kilograms because they were 45 micrograms off the French prototype — about the weight of an eyelash. This meant that companies that produce weights based on the NIST standards had to reissue their own weights, and they were not happy about it. Lawmakers were called. NIST was accused of being incompetent. In the end, it turned out that the problem stemmed from le grand K, not NIST.
If that seems like a lot of uproar over an infinitesimal change in the mass of an object, consider this: The effectiveness of filters on diesel engines is determined by measuring the mass of the soot they capture — in micrograms. “There’s a lot that rides on these sorts of things that people take for granted...."
MORE: https://www.washingtonpost.com/news/spea...s-massive/
EXCERPT: [...] Here's the problem with the current standard kilogram: It's losing weight. It now is ever-so-slightly lighter than the once-identical “witness” cylinders stored in labs around the world. Scientists don't know whether the BIPM prototype is losing mass, perhaps because of loss of impurities in the metals, or if the witnesses are gaining mass by accumulating contaminants.
Either way, the whole thing is a “huge inconvenience,” Pratt said. Several years ago, NIST had to reissue certificates for its kilograms because they were 45 micrograms off the French prototype — about the weight of an eyelash. This meant that companies that produce weights based on the NIST standards had to reissue their own weights, and they were not happy about it. Lawmakers were called. NIST was accused of being incompetent. In the end, it turned out that the problem stemmed from le grand K, not NIST.
If that seems like a lot of uproar over an infinitesimal change in the mass of an object, consider this: The effectiveness of filters on diesel engines is determined by measuring the mass of the soot they capture — in micrograms. “There’s a lot that rides on these sorts of things that people take for granted...."
MORE: https://www.washingtonpost.com/news/spea...s-massive/
