Category Archives: Science News

The death of Le Grand K

Last Friday, the 26th General Conference on Weights and Measures voted to replace “Le Grand K”, the 129 year old physical prototype of the kilogram, with a new measure based on physical constants. The new definition, which comes in to force next spring, is now fixed by defining the Plank constant as exactly 6.626 070 15 x 10-34 Joule seconds. 

The kilogram was the last SI unit based on a physical prototype (which means that until next year, Le Grand K is, by definition, exactly one kilogram). Other prototypes, such as the physical meter, have been long since retired. This redefinition is a triumph of high-precision experimental physics. The problem with physical prototypes for units is that they can change. Le Grand K, for example, has been losing mass, to the tune of about 50 micrograms (5 parts in 100 million), possibly because the identical cylinders it is compared to have gotten dirty from being handled more often.

Farewell Le Grand K! Thank you for your service!

Keeping up with science policy

If you have three minutes every month to devote to keeping up with science policy, I highly recommend subscribing to APS’s Signal Boost. Signal Boost is a monthly video update about key developments in science policy. Among other things, they provide critical information on the budgeting process for science funding in the House and Senate along with how to contact your elected officials about each issue. Scientists are a small group, so we need to speak up to be heard.

This month: appropriations and a bill to fight harassment in STEM: