Policy-makers along with the meteorologists from 60 countries all over the world have come to a unanimous decision. The decision is with regard to change the definition for the four units of measurement. A meeting was held today at the General Conference on Weights and Measures in Versailles, France. There, the delegates voted in favor of getting the SI units redefined whereby the world’s definition of the kilogram, the ampere, the Kelvin and the Mole will be changed. The changes will come into effect on 20th May 2019. There are a total of seven base units of the SI, which include the second, Kilogram, Meter, Kelvin, Ampere, Candela and Mole.
For quite a long time, some of these have been based on physical constants. For instance, the meter has got defined since 1983 as the length of the distance traveled by light in vacuum in a time interval of 1/299 792 458 seconds. Now, the four that the metrologists recently agreed to redefine, were previously based on either an object, phenomenon or on an experiment. This basically means that the value is not at all universal in nature. The decision that has been taken by the metrologists clearly means that all seven SI units will now get defined on the basis of physical constants. The biggest change will come forth on Kilogram. Now the kilogram will be defined in terms of h, the Planck constant. The ampere will get set by the elementary electrical charge e. The definition of Kelvin will be framed by taking the fixed numerical value of the Boltzmann constant k. The value will be 1.380 649 x 10ˉ²³. The mole will be measured by the Avogadro constant, which contains typically 6.02 214 076 x 10²³ elementary entities. This particular number is the fixed numerical value of the Avogadro constant.
In our day to day lives, the new units of SI will have very little immediate consequence in a practical manner. The units may get defined differently; still, the primary objective has been to keep their size the same. Still, defining the units purely based on physical constants clearly means that the scientists will manage to measure them at any particular place or time as well as on any scale.
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