Latest values of fundamental physics constants

Scientists from the National Institute of Standards and Technology regularly collaborate with researchers around the world to collate the world’s most accurate values of the basic constants appearing in the laws of nature, such the masses and magnetic moments of the electron and muon as well as Newton’s gravitational constant.

Tiesinga et al. report the most recently available constants and conversion factors of physics and chemistry recommended by the Committee on Data of the International Science Council (CODATA), which take into account all relevant theoretical and experimental data available through Dec. 31, 2018.

“The revision of the International System of Units had a profound impact on our knowledge of the values of the fundamental constants,” said author Eite Tiesinga. “It not only led to exact values for a number of constants that previously had uncertainties, but also a significant, sometimes more than an order of magnitude, reduction of uncertainties for many others.”

The improvements include a decrease in the uncertainty of the fine-structure constant and nearly two orders-of-magnitude improvements in elementary particle masses (in kilograms) due to the transition to the revised International System of Units (SI) with its exact value for the Planck constant.

Because the elementary charge, the Boltzmann constant, and Avogadro constant have exact values in the revised SI, many other constants are either exact or have significantly reduced uncertainties.

“The major reduction in uncertainties for many constants, in particular those that give properties of fundamental particles and simple atomic systems, will provide much sharper tools for researchers interested in those areas, possibly allowing them to focus on the discovery of new physics that would otherwise be undetectable,” said author David Newell.

Source: “CODATA recommended values of the fundamental physical constants: 2018,” by Eite Tiesinga, Peter J. Mohr, David B. Newell, and Barry N. Taylor, Journal of Physical and Chemical Reference Data, (2021). The article can be accessed at https://doi.org/10.1063/5.0064853 .