Weighty decision! Kilogram definition changed will be applicable since May 2019

NP NEWS 24 ONLINE – Humanity just made a weighty decision. On Friday, representatives of more than 60 nations, gathered in Versailles, France, approved a new definition for the kilogram.

Since the 19th century, scientists have based their definition of the fundamental unit of mass on a physical object — a shining platinum-iridium cylinder stored in a locked vault in the bowels of the International Bureau of Weights and Measures (BIPM) in Sevres, France.

For 130 years, the kilogram has been defined as the exact weight of a cylinder of platinum-iridium held in a triple-locked vault in Paris. Metrologists — experts in the science of measurement — refer to the metal lump as the International Prototype Kilogram or IPK. Others call it “Le Grand K.” It is the one true kilogram in the world, upon which all measures of mass on Earth depend.

A kilogram was equal to the heft of this aging hunk of metal, and this cylinder, by definition, weighed exactly a kilogram. If the cylinder changed, even a little bit, then the entire global system of measurement had to change, too.

The redefinition is the result of a decades-long, worldwide quest to measure Planck’s constant precisely enough that the number would stand up to scientific scrutiny.

Though the newly defined kilogram won’t affect your bathroom scale, it will have practical applications in research and industries that depend on meticulous measurement.

With Friday’s vote, scientists redefined the kilogram for the 21st century by tying it to a fundamental feature of the universe — a small, strange figure from quantum physics known as Planck’s constant, which describes the smallest possible unit of energy.

The change, which will come into force in May 2019, will draw the curtain on the use of human-scale physical objects to define measurement units and thus end an important era in the history of science.