The kilogram is one of the basic units of the International System of Units, considered as the unit of mass. The kilogram has been defined since 1889 by an international prototype, which is a platinum and iridium cylinder that is currently kept at the International Office of Weights and Measures in Paris. In other words, one kilogram equals the weight of this cylinder.
The kilogram is the only unit that is still defined based on a pattern or physical object, the rest of the units (meter, second, ampere, kelvin, mole, and candela) are based on fundamental physical properties; for example, the meter is defined on the speed of light. The kilogram is represented by the symbol Kg.
Measurements of the prototype of the kilogram in the last century have indicated that its mass has varied slightly about 50 micrograms lower than when it was manufactured in 1879. The International Bureau of Weights and Measures is considering redefining the unit of mass, with the aim that This unit is stable, since the stability of the kilogram is crucial because it forms the base from which many other units of weight are obtained.
Today, scientists around the world are working on a new definition that has an absolute physical phenomenon as a reference. Apparently the possible solution is based on the " Plank constant " which is fixed and remains unchanged, but experts in mass metrology ask for unanimous and experimental conclusions before changing the definition.
