ephemeris time

ephemeris time
The uniform measure of time defined by the laws of dynamics and determined in principle from the orbital motions of the planets, specifically the orbital motion of the earth as represented by Newcomb’s Tables of the Sun. An ephemeris day equals 84,600 ephemeris seconds. An ephemeris second was the fundamental unit of time of the International System of Units of 1960; it equals 1/31556925.9747 of the tropical year defined by the mean motion of the sun in longitude at the epoch 1900 January 0 day 12 h. Also known as terrestrial dynamical time.

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  • Ephemeris time — (ET) is a time scale used in ephemerides of celestial bodies, in particular the Sun (as observed from the Earth), Moon, planets, and other members of the solar system. This is distinct from Universal Time (UT): the time scale based on the… …   Wikipedia

  • ephemeris time — Astron. time measured by the orbital movements of the earth, the moon, and the planets. [1945 50] * * * ▪ chronology       (ET), the first dynamical time scale in history; it was defined by the International Astronomical Union in the 1950s and… …   Universalium

  • ephemeris time — efemeridinis laikas statusas T sritis Standartizacija ir metrologija apibrėžtis Tolygiai tekantis laikas, vartojamas kaip nepriklausomas kintamasis dangaus kūnų mechanikos lygtyse. Jo ir pasaulinio laiko skirtumas tikrinamas stebint Mėnulio… …   Penkiakalbis aiškinamasis metrologijos terminų žodynas

  • ephemeris time — /əˈfɛmərəs taɪm/ (say uh femuhruhs tuym) noun Astronomy a measure of time independent of variations in the earth s rotation rate. The ephemeris second is the fundamental unit and is defined as a precise fraction of the tropical year 1900 …  

  • ephemeris time — noun (astronomy) a measure of time defined by Earth s orbital motion; terrestrial time is mean solar time corrected for the irregularities of the Earth s motions • Syn: ↑terrestrial time, ↑TT, ↑terrestrial dynamical time, ↑TDT • Topics:… …   Useful english dictionary

  • ephemeris time — noun a) A former standard astronomical time scale intended to overcome the drawbacks of irregularly fluctuating mean solar time, superseded in the 1970s. b) A modern relativistic coordinate time scale …   Wiktionary

  • ephemeris time — ephem′eris time n. astron. time measured by the orbital movements of the earth, the moon, and the planets • Etymology: 1945–50 …   From formal English to slang

  • ephemeris time — noun Date: 1950 a uniform measure of time defined by the orbital motions of the planets …   New Collegiate Dictionary

  • ephemeris time — noun time on a scale defined by the orbital period rather than the axial rotation of the earth …   English new terms dictionary

  • Time from NPL — Map showing the location of the Anthorn VLF transmitter within Cumbria …   Wikipedia

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