Say hooray to the Big K.
Leaders of the international measurement community will come together tomorrow (Nov 16) in France for an historic vote on changes to the metric system, which would lead to a landmark redefinition of the kilogram.
The proposed redefinition of the International System of Units (SI) – more commonly known as the metric system – will go before the 26th General Conference on Weights and Measures, organised by the International Bureau of Weights and Measures (BIPM).
If endorsed, it will mean all SI units will be defined in terms of fundamental constants of nature (from May next year).
This will spell the end of the reign of the International Prototype of the Kilogram (also known as “Le Grand K” or “Big K”), a cylinder of platinum-iridium stored in a vault at the BIPM in France.
Vacuum-sealed under three bell jars, the metal cylinder goes untouched for years, but is brought out as a benchmark to be weighed against 80 official replicas from laboratories around the world.
Big K has served science and technology well, however, over time, there have been small changes which have left it lighter than its replicas.
“We find ourselves at a landmark moment in our journey,” International Committee for Weights and Measures (CIPM) president Dr Barry Inglis said.
“After years of research, it’s now possible to justify a major revision of the SI. This decision, if taken, will represent a significant scientific achievement.
“This will be a tribute to the commitment of resources within the national metrology institutes throughout the world and BIPM, the scientific expertise and dedication within these institutes, and the great spirit of international cooperation, without which such an accomplishment would not have been possible.”
The National Measurement Institute (NMI) Australia – which Dr Inglis heads as CEO – will be working to ensure there will be no disruption to industry.
However, it said the revised SI would be an essential support to facilitate technological innovation and that the changes would have wide-reaching impact in science, technology, trade, health and the environment, among many other sectors.
IMAGE: Le Grand K – courtesy of the National Institute of Standards and Technology.
