It’s an uncertain world when even the constants aren’t constant…
After more than a century, the international prototype kilogram – a cylindrical chunk of metal stored in a French vault – doesn’t weigh the same as its 40 replicas, distributed worldwide and used to standardize mass measurements. Suspecting that gunk accumulating on the metallic surfaces is to blame, scientists at Newcastle University have developed a high-tech way to clean the standards.
… in the late 1980s, scientists noticed that the original kilogram was about 50 micrograms lighter than its brethren. Because mass measurements are relative, it’s tough to determine whether the replicas are getting heavier or the original is getting lighter.
Read the full story at Wired
