The kilo is one of the four basic measurement units next to the ampere, kelvin and mol that will be redefined by the General Conference on Weights and Measures (CGPM) in November 2018, in what constitutes the largest revision of the International System of Units since its establishment in 1960. The objective of this change is to define these units in relation to fundamental and non-arbitrary constants as it has been up to now.

https://i2.wp.com/altadensidad.com/wp-content/uploads/2017/10/kilo.jpg?w=620&ssl=1

Currently a kilogram is equivalent to the mass that has a cylinder of 4 centimeters of iridium platinum manufactured in London that has been preserved since 1889 in a safe in France. But this original kilo has lost in a century, 50 micrograms. This is because objects can easily lose atoms or absorb molecules from the air, so defining such a unit of measurement is complicated.

https://www.youtube.com/watch?v=XEelttlbo4Y

In everyday life these minimal differences are not important, but in calculations that require extreme precision, measures such as the current ones are of little scientific help. The new kilogram, which will come into force in May 2019, will allow researchers to carry out their experiments and relate them to a constant unit of measurement.