Scientists say goodbye to physical definition of the kilogram

In between coffee breaks and presentations on quantum physics, scientists today voted to redefine the kilogram, the unit that underpins the world’s system of weights. Instead of basing the kilogram’s value on a physical artifact, as has been the case for more than 100 years, it will now be defined using a constant of nature.Its weight, handily, will not change.The vote has been centuries in the making, with scientists describing it as the biggest revolution in measurement since the