**ephemeris second** — Astron. the unit of ephemeris time, defined as a precise fraction of the length of the tropical year 1900. [1965 70] * * * … Universalium

**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

**Second** — This article is about the unit of time. For other uses, see Second (disambiguation). A light flashing approximately once per second. The second (SI unit symbol: s; informal abbreviation: sec) is a unit of measurement of time, and is the… … Wikipedia

**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… … Aviation dictionary

**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** — 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** — An ephemeris (plural: ephemerides; from the Greek word ἐφήμερος ephemeros daily ) is a table of values that gives the positions of astronomical objects in the sky at a given time or times. Different kinds are used for astronomy and astrology.… … Wikipedia

**second** — second1 seconder, n. /sek euhnd/, adj. 1. next after the first; being the ordinal number for two. 2. being the latter of two equal parts. 3. next after the first in place, time, or value: the second house from the corner. 4. next after the first… … Universalium

**American Ephemeris and Nautical Almanac** — The American Ephemeris and Nautical Almanac was published for the years 1855 to 1980, containing information necessary for astronomers, surveyors, and navigators. It was based on the original British publication, The Nautical Almanac and… … Wikipedia

**Coordinated Universal Time** — UTC redirects here. For other uses, see UTC (disambiguation). Coordinated Universal Time (abbreviated UTC) is the primary time standard by which the world regulates clocks and time. It is one of several closely related successors to Greenwich… … Wikipedia