FUNDAMENTAL CONSTANTS
DATA CENTER

MISSION

• provide an international information center on the fundamental constants and closely related precision measurements;

• analyze the consistency of measured values of the constants in order to test fundamental physical theory and to obtain 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;

• serve as the NIST-authorized organization for the interpretation of the International System of Units (SI) in the United States.

CURRENT DIRECTIONS

• Measurement Uncertainty. Contribute to an international effort under the auspices of the Joint Committee for Guides on Metrology (JCGM) to generate and widely distribute guides on expressing measurement uncertainty, and to have them adopted worldwide.

• Information Center. Maintain an extensive collection of reprints and other material relating to fundamental constants and precision measurements in order to respond to inquiries and carry out the next Committee on Data for Science and Technology (CODATA) least-squares adjustment of the constants, which is to be completed by no later than mid-1999 and will provide a new set of recommended values of the constants for international use. This effort includes maintaining the Data Center’s bibliographic database on the fundamental constants on the Web.

• Precision Measurement Grants. Implement policies to ensure that this grant program continues to attract proposals of the highest quality and provides maximum benefit to NIST.

• NIST Journal of Research. Implement policies to ensure that the NIST Journal of Research continues to be a widely read, highly respected scientific publication and an attractive vehicle for NIST scientists to report the results of their research in measurement.

• SI Units. Generate and disseminate publications related to the SI to meet the information needs of the increased users of the SI arising from the Federal Government’s conversion to the SI.

HIGHLIGHTS

• NIST Reference on Constants, Units, and Uncertainty. This is a fully integrated Web site at physics.nist.gov/cuu that provides in-depth information on the fundamental physical constants, the SI, and the expression of uncertainty in measurement.

  The information on the fundamental constants includes the most recent CODATA set of self-consistent values of the basic constants and conversion factors of physics and chemistry in a user-friendly, easily searchable, and printable form. The information on the SI features a concise summary of the essential features of the SI, the rules and style conventions for its use, and the correct typeface to use for symbols in scientific publications. The information on the expression of uncertainty in measurement focuses on the essentials of evaluating and expressing the uncertainty associated with measurement results based on the International Organization for Standardization (ISO) Guide to the Expression of Uncertainty in Measurement and NIST Technical Note 1297, Guidelines for Evaluating and Expressing the Uncertainty of NIST Measurement Results.

• New Interpretation of the SI for the United States. A new interpretation of the SI for use in the United States was published in the 28 July 1998 issue of the Federal Register (FR 63 40334-40340). Since the publication of the 1990 interpretation, the international bodies responsible for the SI made some significant changes to it, and it became necessary to set forth a new interpretation. The changes include: 1) the addition of four new SI prefixes to form decimal multiples and submultiples of SI units; 2) the elimination of the class of supplementary units (the radian and steradian) as a separate class in the SI; and 3) changes in the units not part of the SI that can be used with it. The new Federal Register notice is included in the NIST Reference on Constants, Units, and Uncertainty.

• Precision Measurement Grants. The FCDC awarded, on behalf of NIST, new Precision Measurement Grants to Prof. D.E. Pritchard of MIT and Prof. S.T. Staggs of Princeton University. The grants are in the amount of $50,000 per year, renewable for two additional years. NIST sponsors these grants to promote fundamental research in measurement science in U.S. colleges and universities and to foster contacts between NIST scientists and researchers in the academic community actively engaged in such work.

  The aim of Pritchard's project, "Accurate Atomic Mass Measurements," is to significantly reduce the uncertainty of the measured values of the relative atomic masses of a number of atoms, especially those required for the improved determination of the fine-structure constant, the Avogadro constant, the critical testing of Einstein’s energy-mass relation E = mc², placing limits on the mass of the electron neutrino, and providing improved values of the relative atomic masses of the proton, neutron, and deuteron.

  The aim of Staggs' project, "Measurement of the Polarization of the Cosmic Microwave Background," is to develop a correlation microwave receiver of bandwidth 16 GHz operating at 90 GHz with front-end amplifiers cooled to 15 K and with noise temperatures of less than 50 K, and to use it to make the first observations of the expected 5 µK linear polarization (0.2 ° diameter sky patch) of the cosmic microwave background (CMB).

FUTURE OPPORTUNITIES

TECHNICAL ACTIVITIES 1998 - Contents