Since the year 1889, a kilogram has been defined by a shiny lump of platinum-iridium that has been kept in a special glass case. It is known as the international prototype of the kilogram. But recently, the kilogram has been redefined.
The platinum-iridium prototype was housed at the headquarters of the International Bureau of Weights and Measures (BIPM) just outside Paris. Members of BIPM, which consists of approximately 60 nations, took a decision after a week-long meeting. The meeting took place near the Palace of Versailles. The decision has been made and the kilogram has been redefined.
The kilogram shall now be identified in terms of a tiny but unchanging value called the “Planck Constant”. The voting went in favour of the updating of the definitions for the ampere (electrical current), the kelvin (thermodynamic temperature) and the mole (amount of substance).
the kilogram has been redefined, This change is very important. That is because of the fact that all modern mass measurements are derived from the kilogram. It may be micrograms of pharmaceutical medicine or gold dust, kilos of fruit or fish, or tonnes of steel.
The problem was that the prototype doesn’t always weigh the same. Even inside the three glass bell jars, it picks up microparticles of dirt. It is also affected by the atmosphere. Sometimes cleaning can also affect its mass.
This change in mass can have profound implications. If the prototype loses mass, in theory, atoms would weigh more since the base kilogram must by definition always weigh a kilogram. Scientists have been trying to obtain a constant value for the kilogram that is derived from immutable physics for decades. This is the same way in which other SI units are defined. For example, a metre isn’t 100 centimetres, it’s actually “the length of the path travelled by light in a vacuum during a time interval of 1/299,792,458 of a second”.
Thus, the kilogram has been redefined in accordance with the Plank Constant from quantum physics.
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