The article explains how the kilogram, once defined by a physical artifact known as the International Prototype Kilogram (IPK), was redefined in 2019 based on a fundamental constant of nature—the Planck constant (h). This change was necessary because the IPK’s mass could change over time due to contamination and wear, leading to inconsistencies in measurements worldwide. Scientists and metrology organizations agreed that defining the kilogram using a stable, unchanging natural constant would improve accuracy and reliability.
The redefinition of the kilogram, along with three other SI units, was officially adopted in 2019 after years of research and international collaboration. The Planck constant, a key concept from quantum mechanics, now serves as the basis for the kilogram. This change ensures that the kilogram is no longer dependent on a physical object and instead relies on a universal constant that can be measured with high precision. The shift has far-reaching effects, as the kilogram is used to define many other units of measurement, including force, pressure, and energy.
Source: https://www.nist.gov/si-redefinition/kilogram-present
Keywords: Planck constant, kilogram redefinition, SI units
