Wednesday, June 26, 2019
Revolutionary Change in SI Units:
There was no recent revolutionary change in the International System of Units (SI). However, significant changes were made in 2019, and these changes are referred to as the "New SI."
 |
| Revolutionary change in SI units |
The most notable change in the New SI is the redefinition of several base units based on fundamental constants of nature. The International System of Units is now based on fixed numerical values of seven defining constants. The key changes include:
1. Redefined Kilogram (kg):
The kilogram, which was previously defined by a physical object known as the International Prototype of the Kilogram (IPK), is now defined using the Planck constant (h).
2. Redefined Ampere (A):
The ampere, the unit of electric current, was redefined using the elementary charge (e) to express the relationship between charge and current.
3. Redefined Kelvin (K):
The kelvin, the unit of temperature, was redefined using the Boltzmann constant (k), which relates the average kinetic energy of particles in a gas to the temperature.
4. Redefined Mole (mol):
The mole, the unit of amount of substance, was redefined based on the Avogadro constant (NA), which specifies the number of entities (atoms, molecules, etc.) in one mole.
These changes were aimed at creating a more stable and universally applicable set of measurement standards. The redefined units are based on fundamental constants that are constants of nature and are not subject to change over time.
It's important to check for updates beyond my last training cut-off in January 2022, as there may have been further developments or changes in the field of metrology and the SI system.