universal time


universal time
(often caps.) See Greenwich Time.
Abbr.: UT.
[1885-90]

* * *

Mean (solar) time of the Greenwich meridian (0° longitude).

Universal Time replaced the designation Greenwich Mean Time in 1928; since 1972 it has been based on international atomic time, a uniform time derived from the frequences of certain atomic transitions and measured by an atomic clock. For most purposes, it is now identical to Greenwich Mean Time.

* * *

      the mean solar time of the Greenwich meridian (0° longitude). Universal Time replaced the designation Greenwich Mean Time in 1928; it is now used to denote the solar time (q.v.) when an accuracy of about one second suffices. In 1955 the International Astronomical Union defined several categories of Universal Time of successively increasing accuracy. UT0 represents the initial values of Universal Time obtained by optical observations of star transits at various astronomical observatories. These values differ slightly from each other because of the effects of polar motion (q.v.). UT1, which gives the precise angular coordinate of the Earth about its spin axis, is obtained by correcting UT0 for the effects of polar motion. Finally, an empirical correction to take account of annual changes in the Earth's speed of rotation is added to UT1 to convert it into UT2. Coordinated Universal Time (q.v.), the international basis of civil and scientific time, is obtained from an atomic clock that is adjusted in epoch so as to remain close to UT1; in this way, the solar time that is indicated by Universal Time is kept in close coordination with atomic time.

* * *


Universalium. 2010.

Look at other dictionaries:

  • Universal Time — (UT) is a timescale based on the rotation of the Earth. It is a modern continuation of Greenwich Mean Time (GMT), i.e., the mean solar time on the meridian of Greenwich, and GMT is sometimes used loosely as a synonym for UTC. In fact the… …   Wikipedia

  • Universal Time — n. Greenwich mean time used as a basis for standard time: cf. COORDINATED UNIVERSAL TIME: abbrev. UT …   English World dictionary

  • Universal Time — Die Universal Time (UT) ist die durch astronomische Beobachtung gewonnene mittlere Ortszeit des durch die Sternwarte von Greenwich führenden Nullmeridians. Sie ist eine universelle Zeitskala, welche die wahre Erdrotation widerspiegelt. In den… …   Deutsch Wikipedia

  • Universal Time — A measure of time that conforms, within a close approximation, to the mean diurnal rotation of the Earth and serves as the basis of civil timekeeping. Universal Time (UT1) is determined from observations of the stars, radio sources, and also from …   Military dictionary

  • Universal Time — noun A measure of time that conforms, within a close approximation, to the mean diurnal rotation of the Earth and serves as the basis of civil timekeeping. Universal Time (UT1) is determined from observations of the stars, radio sources, and also …   Wiktionary

  • universal time — A measure of time that conforms, within a close approximation, to the mean diurnal rotation of the earth and serves as the basis of civil timekeeping. Universal Time is based on mean sidereal time as measured in Greenwich. It is approximately… …   Aviation dictionary

  • Universal Time — (UT or Z)    the correct name for the time system previously called Greenwich Mean Time (GMT): the standard time at longitude 0°. Universal Time is five hours later than Eastern Standard Time in the U.S. It is always stated on the 24 hour clock;… …   Dictionary of units of measurement

  • universal time — noun the local time at the 0 meridian passing through Greenwich, England; it is the same everywhere • Syn: ↑Greenwich Mean Time, ↑Greenwich Time, ↑GMT, ↑UT, ↑UT1 • Hypernyms: ↑time • Hyponym …   Useful english dictionary

  • Universal Time — /junəvɜsəl ˈtaɪm/ (say yoohnuhversuhl tuym) noun 1. a system of time measurement based on Greenwich Mean Time, but counted from 0 h, which is equivalent to midnight Greenwich Mean Time, introduced in 1928 and used internationally until the… …   Australian English dictionary

  • universal time — pasaulinis laikas statusas T sritis automatika atitikmenys: angl. universal time vok. Weltzeit, f rus. всемирное время, n; мировое время, n pranc. temps universel, m …   Automatikos terminų žodynas


Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.