# solar time

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Related to solar time: Equation of time

## solar time,

timetime,
sequential arrangement of all events, or the interval between two events in such a sequence. The concept of time may be discussed on several different levels: physical, psychological, philosophical and scientific, and biological.
defined by the position of the sun. The solar dayday,
period of time for the earth to rotate once on its axis. The ordinary day, or solar day, is measured relative to the sun, being the time between successive passages of the sun over a stationary observer's celestial meridian.
is the time it takes for the sun to return to the same meridian in the sky. Local solar time is measured by a sundialsundial,
instrument that indicates the time of day by the shadow, cast on a surface marked to show hours or fractions of hours, of an object on which the sun's rays fall.
. When the center of the sun is on an observer's meridian, the observer's local solar time is zero hours (noon). Because the earth moves with varying speed in its orbit at different times of the year and because the plane of the earth's equator is inclined to its orbital plane, the length of the solar day is different depending on the time of year. It is more convenient to define time in terms of the average of local solar time. Such time, called mean solar time, may be thought of as being measured relative to an imaginary sun (the mean sun) that lies in the earth's equatorial plane and about which the earth orbits with constant speed. Every mean solar day is of the same length. The difference between the local solar time and the mean solar time at a given location is known as the equation of time. Tables used by navigators list the equation of time for different times of year so that an observer can calculate his mean solar time from his local solar time (found by determining the sun's hour anglehour angle,
in astronomy, a coordinate in the equatorial coordinate system. The hour angle of a celestial body is the angular distance, expressed in hours, minutes, and seconds (one hour equals 15 degrees), measured westward along the celestial equator from the observer's
). Mean solar time is the basis for civil timecivil time,
local time based on universal time. Civil time may be formally defined as mean solar time plus 12 hr; the civil day begins at midnight, while the mean solar day begins at noon.
and standard timestandard time,
civil time used within a given time zone. The earth is divided into 24 time zones, each of which is about 15° of longitude wide and corresponds to one hour of time. Within a zone all civil clocks are set to the same local solar time.
.

## solar time

1. Short for mean solar time.
2. Short for apparent solar time.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006

## solar time

[′sō·lər ′tīm]
(astronomy)
Time based on the rotation of the earth relative to the sun.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
It is seen that the thermal resistance decreases with increasing solar time for all inclination angles.
At a fixed solar time 25% of the erythemal irradiances encountered during the season lie between two adjacent curves or, when thick clouds are present, beneath the bottom curve in each figure.
Figure 6(b) shows a bitmap of the thermal distances of the crossings between all the days in 2005 and their comparable days under calendar criterion with the same solar time during 2005.
The central and the most imposing instrument, the Samrat Yantra was used to measure solar time, as well as to measure the sun's declination, i.e.
Sidereal time agrees with solar time on about September 23 each year and from then on gains about 4 minutes (3m 56s) each day on solar time.
The US could get a running start at curbing its greenhouse-gas emissions by shifting its energy mix more rapidly towards natural gas in the next few years, allowing renewable energy sources like wind and solar time to gain ground.
They discuss time before the 20th century, solar time, ephemerides, variable earth time, earth rotation and polar motion, ephemeris time, relativity and time, dynamical and coordinate time scales, clock developments, microwave atomic clocks, optical atomic standards, the definition and role of a second, international atomic time, coordinated universal time, time in the solar system, time and frequency transfer, modern earth orientation, international activities, time applications, and the future of timekeeping.
A board sitting on a Los Angeles beach for several hours in June during peak solar time can reach a surface temperature exceeding 130 [degrees]F, or 55 [degrees]F above ambient temperature.
(1) Narrative time in the book, Part I, 1605, Part II, 1615, is solar time. It is that simple.
For solar time it is considered that when the sun goes at its highest point in the sky, it is noon.
The equation of time is a correction to be added to the apparent solar time, as read on a sundial, to obtain mean solar time, as commonly used ( Parr & Gold, 1972) This difference is a consequence of tilt of the Earth's orbit.

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