CODATA recommended values of the fundamental physical constants: 2018

Area of Science:

• Physics
• Chemistry
• Metrology

Background:

• The Committee on Data of the International Science Council (CODATA) periodically updates recommended values for fundamental physical and chemical constants.
• Accurate constants are crucial for scientific research, technological applications, and international standardization.

Purpose of the Study:

• To report the 2018 self-consistent recommended values of physical and chemical constants and conversion factors.
• To discuss improvements in data consistency and identify remaining inconsistencies.

Main Methods:

• A least-squares adjustment of all available theoretical and experimental data up to December 31, 2018.
• Incorporation of the revised International System of Units (SI) with an exact Planck constant.

Main Results:

• Significant reduction in uncertainty for the dimensionless fine-structure constant.
• Nearly two orders of magnitude improvement in particle mass accuracy in kilograms.
• Many constants are now exact or have substantially reduced uncertainties due to the revised SI.
• Remaining inconsistencies noted for the gravitational constant and muon magnetic-moment anomaly.
• Partial resolution of the proton charge radius puzzle through improved hydrogen energy level measurements.

Conclusions:

• The 2018 CODATA adjustment provides a highly accurate and consistent set of fundamental constants.
• The transition to the revised SI has led to major improvements in the accuracy and definition of many physical quantities.
• Ongoing research is needed to address remaining inconsistencies in fundamental constants.