KPC3371: Redefinition of the SI Base Units

In our daily lives, we constantly measure everything. For example, when we wake up in the morning, the first thing we do is check the time, temperature, and the level of fine dust, etc. In addition, we check how fast we travel when we drive to work and the distance from our home to the final destination. Such numerical measurements require standard units so that the temperature, mass, and length can be expressed objectively. The measurement units that were derived from the dimensions of human body parts or natural objects in the past have become increasingly accurate by incorporating advanced technology and science with the evolution of human civilization.

The International System of Units (SI) has evolved to become a coherent system even though some units still remain unstable. For example, the magnitude of a kilogram has been defined as the mass of an object called the `International Prototype of the Kilogram` which was made out of a platinum- iridium alloy since 1889. However, the mass of the prototype has over time changed by tens of micrograms (㎍). As unstable units lead to unreliable measurements, it has become even harder to completely trust the measurements used in our everyday lives and across the industries.

On 16 November 2018, at the 26th General Conference on Weights and Measures in Versailles, France, the representatives of countries from around the world redefined the four out of seven base units of the SI, the most significant revisions to the SI since its establishment: the kilogram, the ampere, the kelvin, and the mole. The fixed numerical values of the Planck constant (h), Elementary charge (e), Boltzmann constant (k), and Avogadro constant (NA), are what will now be used for the new SI definitions. The invariable units with greater stability and universal accessibility will officially come into effect on World Metrology Day, 20 May 2019.

The redefinition of the SI base units will not make any perceivable difference to our daily lives, but will lay a stable foundation for the future scientific and technological innovations. Thus, advanced technologies and industries, such as biotechnology and semiconductors will be able to avoid any fatal errors and prepare for the future with the invariable units.