Until now, it has been defined as the mass of a platinum-iridium lump, the so-called Grand K, that is kept in a secured vault on the outskirts of Paris. It has been the world's one true kilo, against which all others were measured, since 1889.
from Top World News- News18.com https://ift.tt/2FpYsNE
from Top World News- News18.com https://ift.tt/2FpYsNE