After 130 years, scientists change definition of Kilogram, Ampere, Kelvin, Mole

After decades, scientists have agreed to refine the Kilogram, along with other International System of Units including Ampere, Kelvin and Mole, landmark in scientific measurement.

After having a constant definition for 130 years, around 60 nations got together to change the definition of the Kilogram unit, which was previously defined using a platinum-iridium cylinder alloy placed in Paris, called the ‘Grand K’.

The cylinder went through few problems over time, eventually leading to nations redefining the unit at the General Conference on Weights and Measures after a historic vote. According to the new definition, the unit is now defined completely by natural phenomenon.

It is defined in terms of the Planck’s constant (h), an equation in physics. Thus, the new value of kg now is defined from the Planck’s constant whose value is set at 6.62607015 x 10^?34kg m²/s. The new definition will be put into place on May 20, 2019.

Albeit, this redefinition won’t really affect the general practices like measuring scales and changes in grams/kilograms in markets, but the change will put precision measurements on a firmer foundation, as per Science News. The Director of research, Jan-Theodoor Janssen, mentioned the SI redefinition as a ‘landmark moment in scientific measurement’.

The Kilogram unit was defined by a set of weight placed in a closed environment from which various sample weights were taken. However, with passing time, differences started to appear between the different samples and the standard.

The new formula-based definition will have more benefits such as the formula cannot pick up dust particles, or won’t decay over time, or be dropped or damaged like the physical object, whose weight changes over time. It is also expected to be more accurate, reported Metro.

Other than Kilogram, other units including the unit for electric current Ampere, temperature Kelvin, and amount of substance Mole have also been altered. The Ampere is now defined from the elementary electrical charge (e), the Kelvin is redefined as the Boltzmann constant (k), and the Mole is now tied to the Avogadro constant (N_A), all the redefined definitions based on fundamental constants of nature.