Nick van Remortel demystifies natural unit systems — and advises what to do when you see a mass expressed in GeV. Several unit systems for describing the natural world exist. The International System ...

A new definition of the kilogram is required, an international team of scientists contends. The current one is imprecise, they say, because it is not linked to an unvarying property of nature. The ...

The redefinition of several physical base units planned for 2018 requires precise knowledge of the values of certain fundamental physical constants. Scientists are working hard to meet the deadlines ...

The new kilogram (unit of weight) and three other new base units - ampere (electric current), Kelvin (temperature) and mole (amount of substance such as atoms) - will now not be based on 'physical ...