At the general conference on weights and measures in Versailles, representatives from 57 nations will vote for change. Scientists first use a supremely sensitive piece of equipment called a Kibble balance to calculate Planck’s constant from a 1kg reference mass. Planck’s constant is proportional to the energy needed to balance the mass. Then, armed with a precise value for Planck’s constant, researchers can do the reverse, and use the balance to measure unknown masses. Planck’s constant never changes, so it is the same for all time.

Source: The Guardian November 09, 2018 12:48 UTC