Abstract
New recommended values of the fundamental physical constants have recently been published by the Task Group on Fundamental Constants established in the Committee on Data for Science and Technology (CODATA) after an interval of 13 years. Technology in experiments and theories in physics developed over the past decade have improved the uncertainties of many of them to about 1/5 to 1/160. The best values found for these constants are indispensable to solidify the validity of the models we rely on in describing the nature. Improvements in the uncertainties of the constants also suggest a possible new definition of the kilogram. In this article the measurement technology of the Avogadro constant and the Planck constant, that determine the relationship between the microscopic and macroscopic quantities, are reviewed, and the possibility for realizing a new definition of the kilogram is discussed.
