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Topic: Mean solar time


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  Solar time - Wikipedia, the free encyclopedia
Mean solar time is artificial clock time adjusted via observations of the diurnal rotation of the fixed stars to agree with average apparent solar time.
The difference between apparent solar time and mean solar time is called the equation of time.
Babylonian astronomers knew of the equation of time and were correcting for it as well as the different rotation rate of stars, sidereal time, to obtain a mean solar time much more accurate than their water clocks.
en.wikipedia.org /wiki/Mean_solar_time   (618 words)

  
 Solar time -- Facts, Info, and Encyclopedia article   (Site not responding. Last check: 2007-10-09)
Solar time can be measured by a (Timepiece that indicates the daylight hours by the shadow that the gnomon casts on a calibrated dial) sundial.
Mean solar time is artificial (A timepiece that shows the time of day) clock time adjusted via observations of the (additional info and facts about diurnal rotation) diurnal rotation of the fixed stars to agree with average apparent solar time.
The earliest were clepsydras or (Clock that measures time by the escape of water) water clocks, used for almost four millennia from as early as the mid second millennium BC until the early (additional info and facts about second millennium) second millennium.
www.absoluteastronomy.com /encyclopedia/s/so/solar_time.htm   (571 words)

  
 MSN Encarta - Time
The concept that time is a fourth dimension—on a par with the three dimensions of space: length, width, and depth—is one of the foundations of modern physics.
Universal time is simply the mean solar time measured at the Greenwich meridian, which is designated 0° longitude and from which the longitude of all points on the surface of Earth are measured.
Because the basis of mean solar time relates to the motion of a hypothetical sun, scientists established a base position from which the mean time is calculated.
encarta.msn.com /encnet/refpages/RefArticle.aspx?refid=761561386   (1388 words)

  
 The Columbia Encyclopedia, Sixth Edition: solar time @ HighBeam Research   (Site not responding. Last check: 2007-10-09)
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.
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.
Mean solar time is the basis for civil time and standard time.
www.highbeam.com /library/doc0.asp?DOCID=1E1:solartim&refid=ip_encyclopedia_hf   (297 words)

  
 Search Encyclopedia.com
Greenwich mean time Greenwich mean time or Greenwich meridian time (GMT), the former name for mean solar time at the original site of the Royal Observatory in Greenwich, England, which is located on the prime meridian.
mean mean, in statistics, a type of average.
The arithmetic mean of a group of numbers is found by dividing their sum by the number of members in the group; e.g., the sum of the seven numbers 4, 5, 6, 9, 13, 14, and 19 is 70 so their mean is 70 divided by 7, or 10.
www.encyclopedia.com /searchpool.asp?target=@DOCTITLE+mean   (143 words)

  
 Greenwich Mean Time - Wikipedia, the free encyclopedia   (Site not responding. Last check: 2007-10-09)
Greenwich Mean Time (GMT) is the mean solar time at the Royal Greenwich Observatory in Greenwich near London, England, which by convention is at 0 degrees geographic longitude.
Theoretically, noon Greenwich Mean Time is the moment when the Sun crosses the Greenwich meridian (and reaches its highest point in the sky in Greenwich).
Because of the Earth's uneven speed in its elliptic orbit, this event may be up to 16 minutes off apparent solar time (this discrepancy is known as the equation of time); but this is averaged out over the year through the use of the mean sun.
www.encyclopedia-online.info /GMT   (355 words)

  
 NASS FAQ - Glossary
Equation of Time: the time difference between Local Apparent Time (apparent solar time) and mean solar time at the same location.
It arises because of the elliptical orbit of the Earth, and the tilt of the Earth’s axis to the ecliptic.
Mean Solar Time: the authoritative (by the National Physical Laboratory) definition is: a measure of time based conceptually on the diurnal motion of the fictitious mean Sun, under the assumption that the Earth's rate of rotation is constant.
www.sundials.org /faq/glossary/glossary.htm   (1266 words)

  
 Solar time - Wikipedia
Mean solar time is based on a fictional mean sun which travels at a constant rate throughout the year.
The length of a mean solar day is a constant 24 hours throughout the year although, as noted above, the amount of daylight varies.
The difference between apparent solar time and mean solar time, which is sometimes as great as 15 minutes, is called the equation of time.
wikipedia.findthelinks.com /so/Solar_time.html   (221 words)

  
 Time Scales
In this case ``mean'' means the average obtained by considering the rotation of the earth in the absence of the annual variations caused by obliquity and eccentricity.
Although the term GMT was not explicitly used, the standard time for legal purposes in the United States specified by 15USC261 (the Calder Act) was defined to be based on the mean astronomical time of meridians spaced at 15-degree intervals west of Greenwich; i.e., GMT.
Although the term GMT was not explicitly used, the standard time for legal purposes in the United States specified by 15USC261 was clarified and reaffirmed to be based on the mean solar time of meridians spaced at 15-degree intervals west of Greenwich; i.e., GMT.
www.ucolick.org /~sla/leapsecs/timescales.html   (12419 words)

  
 [No title]   (Site not responding. Last check: 2007-10-09)
The interval of time required for 360 degrees of rotation of the earth, causing a given star to return to exactly the same position in the sky, is 23 hours 56 minutes 4.09 seconds of mean solar time and is known as the sidereal day.
Apparent Solar Time and Mean Solar Time: Apparent Solar Time is the system of days and hours which goes strictly by the sun itself, only 4 days in the entire year is the sun over the meridian exactly on time.
Mean Solar Time is the system of days and hours mathematically computed in order to give the average value to every hour and day.
cas.memphis.edu /~hkung/geog1010/Lecture3-Time.DOC   (982 words)

  
 Time   (Site not responding. Last check: 2007-10-09)
Solar Time is time measured with respect to the Sun.
Mean Solar Time is referred to an imaginary body, the Mean Sun, which travels around the celestial equator (not the ecliptic!) at a constant rate of 360º per year.
Solar Time is the time given by a sundial, i.e.
www.astunit.com /tutorials/time.htm   (365 words)

  
 UTC Definition / UTC Research   (Site not responding. Last check: 2007-10-09)
It is a modern continuation of the Greenwich Mean Time (GMT), i.e., the mean solar time on the meridian of Greenwich, England, which is the conventional 0-meridian for geographic longitude.
Time zonesTime zones are areas of the Earth that have adopted the same standard time, usually referred to as the local time.
Time zones partially rectified the problem by setting the clocks of a region to the same mean solar time.
www.elresearch.com /UTC   (340 words)

  
 Technical Notes on Mars Solar Time   (Site not responding. Last check: 2007-10-09)
The mean interval between the repetition of the planet's perihelion passage, or anomalistic year, is 668.6146 sol, and corresponds to the rate of advance of the planet's orbital mean anomaly.
Time tags for the Mars Pathfinder Lander were referenced with respect to the local true solar time, with elapsed sols reckoned from the local true solar midnight preceding its landing, but designated with a starting number "1" rather than zero.
The derivation of mission time adopted by the Mars Exploration Rover Project at the Jet Propulsion Laboratory is an offset modification of an evenly advancing mean solar time, based on its definition by Roncoli et al.
www.giss.nasa.gov /tools/mars24/help/notes.html   (2462 words)

  
 solar time on Encyclopedia.com
Solar collectors can be seen on some of the roofs in The Village in Benicia, California, which was one of the first mass produced solar residence developments.
Solar specialist Mario Quixtan installs inverter boxes in the attic of the low-income Potrero buildings in Richmond, California, on Friday, November 8, 2002.
Solar specialist Arnold Tech, left, and Bear Thrush install electric solar panels on the rood of the Deliverance Temple I apartments in Richmond, California, on Friday, November 8, 2002.
www.encyclopedia.com /html/s1/solartim.asp   (719 words)

  
 The Time of Internet - Solar Time   (Site not responding. Last check: 2007-10-09)
Since time began, the time flow on the Earth is ruled by the apparent motion of the Sun in the sky.
To avoid this drawback, it was defined the mean solar time that has the mean solar day, equal to the mean duration of all days of year, as measurement unit.
It can be noted that the two times are equal four times a year and that the difference has a minor amplitude swing in the period spring-summer and a major amplitude swing in the period fall-winter.
toi.iriti.cnr.it /uk/suntime.html   (313 words)

  
 [No title]   (Site not responding. Last check: 2007-10-09)
Greenwich Mean Time (GMT) is mean solar time at the Royal Greenwich Observatory in Greenwich, London, England, which by convention is at 0 degrees geographic longitude.
Noon Greenwich Mean Time is not the moment when the Sun crosses the Greenwich meridian (and reaches its highest point in the sky in Greenwich) because of Earth's uneven speed in its elliptic orbit and its axial tilt.
The fictitious mean sun is the annual average of this nonuniform motion of the true Sun, necessitating the inclusion of mean in Greenwich Mean Time.
www.everybase.com /GMT   (457 words)

  
 Time Keeping in Astronomy
The basis of astronomical time is the rotation of the Earth on its axis.
Note that LMT is not, in general, the same as the the civil time (standard time) at a location since the civil time is the same for all locations in that zone and is the LMT for the zone's standard longitude.
Sidereal time is time kept relative to the stars instead of relative to the sun.
www.astro.ufl.edu /~oliver/ast3722/lectures/CoordsNtime/time.htm   (1576 words)

  
 Longitude and Time Zones
If you set a sundial to be on time at one time of the year then it will run fast or slow at other times of the year.
With zone time we all agree to use the mean solar time of the nearest longitude divisible by 15 deg.
The time we use, (mean) solar time, is related to the position of the sun in the sky, because most of us prefer to be awake or to work when the sun is up.
www.polaris.iastate.edu /NorthStar/Unit2/unit2_sub2.htm   (823 words)

  
 Time and Frequency from A to Z
In the field of time and frequency, the term is generally associated with the hydrogen maser.
An astronomical time scale that is based on the average length of the day, called the mean solar day.
For example, in a true apparent solar time scale, noon is the instant when the Sun transits the local meridian and reaches its highest point in the sky.
tf.nist.gov /general/enc-m.htm   (292 words)

  
 Grok Solar Calculator Usage Information.   (Site not responding. Last check: 2007-10-09)
The Grok Solar Calculator is a CGI (Common Gateway Interface) application that generates for a given location and date, either a formatted HTML table of solar coordinates, a formatted Text table of solar coordinates or a GIF image plot of solar altitude vs. azimuth.
Solar coordinates are calculated using an abbreviated set of terms from the French planetary theory VSOP87 and are referred to the mean dynamical ecliptic and equinox of the date.
Standard time zone boundaries, which in theory, are on longitudes 7.5 degrees east and west of a standard time zone meridian, in practice meander to accommodate local centers of population and political borders.
www.gcstudio.com /calcuse.html   (1583 words)

  
 Solar time - TheBestLinks.com - Mean solar day, Atomic clock, Clock, December, ...   (Site not responding. Last check: 2007-10-09)
Second, due to Earth's axial tilt, the Sun does not move along Earth's celestial equator but usually moves at an angle to it during the year, thus it moves fast or slow depending on whether it is moving toward or away from the equator (see Tropical year).
Consequently, apparent solar days are shorter in March and September than they are in June or December.
An apparent solar day may differ from a mean solar day by as much as 30 seconds, but because many of these large or small days occur in succession, the difference builds up to as much as 17 minutes.
www.thebestlinks.com /Mean_solar_day.html   (642 words)

  
 Coordinated Universal Time (UTC)   (Site not responding. Last check: 2007-10-09)
Basically, the Universal Time systems are coordinated world-wide standards, whereas GMT was a national standard that was used as a de facto world standard.
(Mean solar means that you use average out the seasonal changes due to the earth's elliptical orbit by using a theoretical mean sun rather strictly observing the real one.
Around this time, a second was also redefined in terms of electron transitions in a cesium atom, rather than a certain fraction of a mean solar day.
www.clock.org /~jss/work/time.html   (399 words)

  
 The State Hermitage Museum: Exhibitions
Mean solar time - like true solar time is made up of hours, minutes and seconds that come together to make the day or the year.
The length of each mean day is the same throughout the year and is the product of calculation.
The figure was reached by dividing the total length of the equinoctial year in true solar days by the number of days in a year.
www.hermitagemuseum.org /html_En/12/b2003/hm12_2_7_3_19.html   (116 words)

  
 Greenwich Mean Time - Open Encyclopedia   (Site not responding. Last check: 2007-10-09)
Although not affecting the local time directly, most time zones are based upon this reference as a number of hours and half-hours "ahead of GMT" or "behind GMT".
Civil time, notably the Greenwich Time Signal, in the United Kingdom has now moved to a UTC-based system, though it is still popularly called GMT it is also called Western European Time (WET).
Those countries marked in Dark Blue use European Summer Time and advance their clock one hour in the summer.
open-encyclopedia.com /GMT   (400 words)

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