New definition of Kilogram and other basic units came into effect on 20 May 2019. The change in definitions was scheduled to be effected on World Metrology Day as per the 26th General Conference on Weights and Measures (CGPM) held in November 2018.
The new definitions of basic units revolve around the idea of ‘standard units for all times and for all people.‘ New definitions of four of the seven base units i.e. the kilogram, ampere, kelvin, and mole came into existence, definitions of all of these are now based on physical constants.
International System of Units (SI) aka metric system of measurements has been in practice since 1889 and was formalised in 1960.
Why the change?
It is important to note that the value and amount of kilogram have not been changed in the new definition of kilogram. Only the definition has changed which is more democratic than the earlier one.
International Bureau of Weights and Measures (BIPM), a Paris based international organization is responsible for setting up the global standards for measurement. Since 1889 the mass of a cylinder made of platinum-iridium known as Le Grand K, or International Prototype Kilogram (IPK) has been taken into account as the standard mass. Although this cylinder has been kept inside a jar at BIPM, Paris, it does not hold true as soon as some dust particles settled on it.
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You might be wondering how the tiny dust particle can change the mass of a kilogram. Mass of a dust particle is negligible if we talk about the macroscopic measurements but in case of microscopic measurements which includes pharmaceutical measurements and measurements related to scientific research, this is going comparatively going to be a huge change.
What if kilogram is defined in terms of a natural constant!
To get rid of the aforementioned problem BIPM organized CGPM on November 16, 2018. 60 member countries of BIPM agreed that the kilogram should be defined in terms of the Planck constant, a quantity that relates a light particle’s energy to its frequency.
Plank constant is determined by using Kibble balance (watt balance) which was first developed at National Physical Laboratory by the late physicist Bryan Kibble.
Following the change, all the school and college textbooks are going to be updated and the new definition of kilogram along with other definitions of basic units, which are now based on physical constants will be included in the curriculum.
New Definition of Kilogram And Other SI Units
Physical constants used in the new definitions are listed below.
1 Comment
Brianjousy · March 30, 2020 at 2:37 am
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