PROGRESS IN PRECISION TIMEKEEPING AND TIME DISTRIBUTION

R. Glenn Hall

Peer Reviewed

Abstract: Introduction THERE CAN, OF COURSE, be many kinds of time systems. However, only three fundamentally different kinds of time are in use today. These are: (1) Time based on the rotation of the earth about its axis; (2) Time based on the revolution of the earth about the sun ; (3) Time based on transitions in the cesium atom. Time based on the rotation of the earth is the time system we use for navigation, geodesy, civil time, etc. It has several different forms, all of which are related to each other by rigorous formulae or by appropriate tables. These forms are the various Sidereal times, mean and apparent, and Universal times, UTO, UTI, and UT2. Sidereal time is based on the rotation of the earth with respect to the stars. Mean sidereal time is measured with respect to the mean equinox of date while apparent sidereal time takes into account nutation in right ascension. Universal Time is a very close approximation to mean solar time. Universal Time and Sidereal Time are rigorously related by a formula so that if one is known the other can be found.
Published in: NAVIGATION, Journal of the Institute of Navigation, Volume 15, Number 2
Pages: 154 - 156
Cite this article: Hall, R. Glenn, "PROGRESS IN PRECISION TIMEKEEPING AND TIME DISTRIBUTION", NAVIGATION, Journal of The Institute of Navigation, Vol. 15, No. 2, Summer 1968, pp. 154-156.
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