Fundamental Constants Data Center
Technical 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).
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