A remarkable aspect of this experiment is that the Planck constant, which is the characteristic unit of quantum phenomena, is measured by a two-story-high apparatus, shown in figure 3, that is described by classical mechanics and classical electromagnetic theory. The best value of this basic constant of quantum physics is determined by a watt-balance experiment that compares a watt of electrical power to a watt of mechanical power ( box 3).
The remaining constant in the electron mass equation is the Planck constant. The values of the constants are also available at on the NIST Physics Laboratory Web site, and a searchable bibliographic database on relevant publications is available at. A summary of this adjustment, as well as tables of values of the constants, appears in the Buyers’ Guide that accompanied the August 2000 issue of Physics Today. 4 The most recent set is termed the 1998 recommended values, because it is based on the information available as of 31 December 1998. The task group’s purpose, as stated in the CODATA handbook, is “to periodically provide the scientific and technological communities with a self-consistent set of internationally recommended values of the basic constants and conversion factors of physics and chemistry based on all of the relevant data available at a given point in time.” Based in part on the work of NIST staff, three sets of CODATA-recommended values of the constants and conversion factors have been published, one in 1973, 2 one in 19, 3 and the latest in 19.
In 1969, the Task Group on Fundamental Constants was established by the Committee on Data for Science and Technology (CODATA), which had been founded three years earlier by the International Council of Scientific Unions. 1 Since then, there have been many efforts to determine the best values of the constants. Birge, who published such a study in 1929 as the very first article in what is now the Reviews of Modern Physics.
The idea of making a systematic study of potentially relevant experimental and theoretical information in order to produce a set of self-consistent values of the constants dates back to Raymond T.
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