Weigh to go Canada! The National Research Council of Canada plays key role in redefined kilogram, which comes into effect today
May 20, 2019 – Ottawa, Ontario – National Research Council of Canada
Today marks the moment in time when all units within the International System of Units are based on fundamental constants, rather than artifacts and physical items. This leap in science is due in no small part to the National Research Council’s (NRC) contribution of a measurement of Planck's constant.
The scientific community had been pursuing a better, more accurate definition of a kilogram — with NRC scientists providing a key value in its calculation. The new definition, which was adopted at the General Conference on Weights and Measures in Versailles in November 2018, is part of an ongoing worldwide effort to have all measurements in the International System of Units based on fundamental laws of nature instead of imprecise physical artifacts.
The change in how a kilogram is now defined won’t affect most day-to-day applications such as shoppers weighing produce at the store or buying a kilogram of sugar, but it will have significant implications for the measurements that researchers and technology manufacturers rely upon.
“Being able to define the Planck constant, and in so doing accurately calculate the actual value of a kilogram, has been a goal of scientists around the world for over 30 years. The NRC did not achieve this milestone on its own. We were part of a collaborative community of global scientists and government partners in Canada who supported and encouraged this discovery.”
Dr. Alan Steele, Canada’s Chief Metrologist, Director General,Metrology Research Centre, National Research Council of Canada
Specialists from the NRC's Metrology team contributed a value of Planck's constant — a measure of action in quantum mechanics that determines mass — with the lowest uncertainty ever achieved: 9.1 parts per billion.
To achieve such precision, the team had to account for seemingly imperceptibly small effects that could influence its Kibble Balance results, including gravitational changes caused by the moon and volume of groundwater from melting snow.
A Kibble Balance is an instrument which measures weight using electromagnetic force. Named for its inventor Dr. Bryan Kibble, it is also known as a watt balance.
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