# The International System of Physical Units is put on a new basis

## New International System of Units: the value of certain fundamental constants are fixed

The International System of Units (SI System of Units) is part of the foundation of science, and a daily tool of scientists and engineers.

## Seven base units form the SI System:

**length**: meter**mass**: kilogram**time**: second**electric current**: Ampere**thermodynamic temperature**: Kelvin (directly linked to Boltzmann constant k)**luminous intensity**: Candela**amount of substance**: mole

### New International System of Units – new framework

The SI system of units has been switched in 2018 from the the previous historic system (1.) where units are fixed and numerical values of fundamental constants are “variable”, i.e. determined experimentally, to the new method (2.) where the numerical values of the set of fundamental constants is fixed, and the units are defined such, that their definition results in the fixed numerical values of the set of fundamental constants. This switch to a new definition of the SI system requires international agreements, and decisions by international organizations, and this process has been completed in 2018.

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