PARIS, FRANCE — Scientists from more than 60 countries and regions gathering in France agreed on Friday to redefine the value of a kilogram in terms of “the Planck constant”, a “fundamental constant of quantum physics”, which they said would improve the accuracy of scientific measurements, according to the International Bureau of Weights and Measures (BIPM).
After a week-long meeting at the Palace of Versailles, outside Paris, BIPM members decided to “bring an end to the use of physical objects to define measurement units”, and update definition for the kilogram in terms of constants that “will open the opportunity for the use of new technologies, including quantum (ones)”.
Since 1889, a kilogram has been defined as a cylinder made out of a platinum-iridium alloy and known as the International Prototype of the Kilogram.
“But, its stability during this period could only be confirmed by comparisons with identical copies, which is a difficult process and potentially inaccurate,” the bureau argued.
Scientists also agreed to redefine ampere by the elementary electrical charge, the kelvin by the Boltzmann constant and the mole by the Avogadro constant.
“The SI (International System of Units) redefinition is a landmark moment in scientific progress,” said Martin Milton, BIPM’s director.
“Using the fundamental constants we observe in nature as a foundation for important concepts such as mass and time means that we have a stable foundation from which to advance our scientific understanding, develop new technologies and address some of society’s greatest challenges,” he added.
According to the BIPM, the new definition would have “wide-reaching impact in science, technology, trade, health and the environment, among many other sectors”.
The revised SI, which aims at facilitating technical innovations, will come into force on May 20, 2019.