sidereal time

sidereal time
time measured by the diurnal motion of stars. A sidereal day is about four minutes shorter than a solar day, with hours, minutes, and seconds all proportionally shorter.
[1805-15]

* * *

      time as measured by the apparent motion about the Earth of the distant, so-called fixed, stars, as distinguished from solar time, which corresponds to the apparent motion of the Sun. The primary unit of sidereal time is the sidereal day, which is subdivided into 24 sidereal hours, 1,440 sidereal minutes, and 86,400 sidereal seconds. Astronomers rely on sidereal clocks because any given star will transit the same meridian at the same sidereal time throughout the year. The sidereal day is almost 4 minutes shorter than the mean solar day of 24 of the hours shown by ordinary timepieces.

      Sidereal time may be defined for any place on the Earth, but in the international system used by astronomers each sidereal day begins at the instant the vernal equinox transits the prime meridian. The vernal equinox is the point on the celestial sphere at which the Sun crosses the plane of the Equator, moving from south to north.

* * *


Universalium. 2010.

Игры ⚽ Нужна курсовая?

Look at other dictionaries:

  • Sidereal time — is a measure of the position of the Earth in its rotation around its axis, or time measured by the apparent diurnal motion of the vernal equinox, which is very close to, but not identical to, the motion of stars. They differ by the precession of… …   Wikipedia

  • sidereal time — n. 1. time measured by the sidereal day: it is divided into the sidereal hour (1/ 24 of a sidereal day), the sidereal minute (1/ 60 of a sidereal hour), and the sidereal second (1/ 60 of a sidereal minute) 2. the hour angle of the vernal equinox …   English World dictionary

  • Sidereal time — Time Time, n.; pl. {Times}. [OE. time, AS. t[=i]ma, akin to t[=i]d time, and to Icel. t[=i]mi, Dan. time an hour, Sw. timme. [root]58. See {Tide}, n.] 1. Duration, considered independently of any system of measurement or any employment of terms… …   The Collaborative International Dictionary of English

  • sidereal time — The sidereal time at any place is the hour angle of the vernal equinox at that place …   Aviation dictionary

  • sidereal time — noun measured by the diurnal motion of stars • Hypernyms: ↑cosmic time • Hyponyms: ↑sidereal day, ↑day, ↑sidereal year, ↑sidereal hour, ↑sidereal month …   Useful english dictionary

  • sidereal time — noun Date: 1764 1. time based on the sidereal day 2. the hour angle of the vernal equinox at a place …   New Collegiate Dictionary

  • sidereal time — side′real time′ n. astron. time measured by the diurnal motion of stars • Etymology: 1805–15 …   From formal English to slang

  • sidereal time — noun Time measured by the apparent diurnal motion of the vernal equinox; approximated by that based on the rotation of the Earth relative to the stars …   Wiktionary

  • sidereal time — noun Astronomy time reckoned from the motion of the earth (or a planet) relative to the distant stars (rather than with respect to the sun) …   English new terms dictionary

  • Greenwich sidereal time — The sidereal time elapsed since the transit of the Greenwich Meridian by the first point of the Aries …   Aviation dictionary

Share the article and excerpts

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