Peso redefinido...

...Finalmente:

https://news.sky.com/story/scientists-throw-weight-behind-changing-the-definition-of-a-kilogram-11555794

Citando:
"Representatives from 60 countries voted in favour of measuring a kilogram by the Planck constant, ending decades of definition by a small piece of metal held in a vault in Paris.

Le Grand K, a small cylinder of titanium alloy, has set the standard since 1889. All the scales in the world are ultimately calibrated against it, even those weighing in pounds and ounces.

Although the mother of all kilograms has only been taken out of its protective case four times in the last century, it has lost atoms and therefore mass. 

The changes will come into force on 20 May next year and also affect the ampere, the kelvin and the mole.

The ampere will now be defined by the elementary electrical charge, the kelvin by the Boltzmann constant and the mole by by the Avogadro constant."