FUNDAMENTAL CONSTANTS
DATA CENTER

MISSION

• provide an international information center on the fundamental constants;
  
• provide periodically sets of recommended values of the constants for international use;
  
• administer the NIST Precision Measurement Grant (PMG) Program;
  
• provide the editorship of the Journal of Research of the National Institute of Standards and Technology; and
  
• serve as the NIST-authorized organization for the interpretation of the International System of Units (SI) in the United States.
  

CURRENT DIRECTIONS

• Information Center and Constants Adjustments. Maintain a fundamental constants library, a Web bibliographic database, respond to inquiries, and carry out the next Committee on Data for Science and Technology (CODATA) least-squares adjustment of the values of the constants.

• Precision Measurement Grants. Continue to fund proposals of the highest quality and that provide maximum benefit to NIST.

• NIST Journal of Research. Continue to ensure that the NIST Journal of Research is a highly respected scientific publication.

• SI Units. Generate and disseminate publications related to the SI.

• Measurement Uncertainty. Under the auspices of the international Joint Committee for Guides on Metrology (JCGM), generate guides on expressing measurement uncertainty.

HIGHLIGHTS

• New Values of the Constants. At midnight on 23 July 1999, the new 1998 self-consistent set of over 300 values of the basic fundamental constants and conversion factors of physics and chemistry recommended by CODATA first became available for world-wide use at the FCDC Web site physics.nist.gov/cuu. The new set is the result of the 1998 CODATA least-squares adjustment of the values of the constants carried out by P.J. Mohr and B.N. Taylor of the Physics Laboratory under the auspices of the CODATA Task Group on Fundamental Constants. Based on all of the data available through 31 December 1998, the new set replaces its immediate predecessor recommended by CODATA in 1986. Because of the new values, the FCDC Web site received over 200,000 hits in October 1999 alone.

• New Precision Measurement Grants. Two new NIST Precision Measurement Grants in the amount of $50,000 were awarded for fiscal year 2000 to Prof. E.G. Gwinn of the University of California (Santa Barbara) and Prof. P. Majumder of Williams College. The aim of Gwinn’s project, "Combining the Quantum Hall and AC Josephson Effects for Electric Current Metrology," is to develop a new quantum standard of electric current by combining the ac Josephson effect and the quantum Hall effect in an integrated, unique way. The aim of Majumder’s project, "New Search for T-Violating Forces in Atomic Thallium," is to develop a high-finesse laser ring-cavity and to use it to search for long-range, electron-nucleon forces in atomic thallium that violate time-reversal symmetry (T) but conserve parity (P).

• Redefinition of the Kilogram. Motivated by recent NIST advances in determining the Planck constant h using a moving-coil watt balance, B.N. Taylor and P.J. Mohr considered the question of redefining the kilogram in such a way that the value of h would be fixed, thereby allowing a watt balance to be used to directly calibrate unknown standards of mass [see Metrologia 36, 63 (1999)]. The proposed definition, analogous to the present definition of the meter which has the effect of fixing the value of the speed of light in vacuum c, is "The kilogram is the mass of a body at rest whose equivalent energy equals the energy of a collection of photons whose frequencies sum to 135 639 274 x 10⁴² Hz." Based on the equations E = mc² and E = h ν, this definition implies h = 6.626 068 9 ... x 10^-34 J s. Such a definition would eliminate the last material artifact from the SI and would allow any laboratory in the world that was so inclined to realize the unit of mass in the SI.

FUTURE OPPORTUNITIES

TECHNICAL ACTIVITIES 1999 - Contents

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Online: April 2000   -   Last update: April 2003