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Topic: Solar time


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In the News (Tue 16 Jul 19)

  
  AllRefer.com - solar time (Astronomy, General) - Encyclopedia
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.
reference.allrefer.com /encyclopedia/S/solartim.html   (354 words)

  
 Solar time - Wikipedia, the free encyclopedia
Apparent solar time is based on the apparent solar day, which is the interval between two successive returns of the Sun to the local meridian.
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.
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/Solar_time   (618 words)

  
 CalendarHome.com - Solar time - Calendar Encyclopedia
The difference between apparent solar time and mean solar time, which is sometimes as great as 15 minutes, is called the equation of time.
It is in the pass from "Apparent solar time is based on the apparent solar day, which is the interval between two successive returns of the Sun to the local meridian.
The length of a solar day varies throughout the year." to "Mean solar time is based on a fictional mean Sun which travels at a constant rate throughout the year.
encyclopedia.calendarhome.com /Solar_time.htm   (809 words)

  
 Solar time - Open Encyclopedia   (Site not responding. Last check: 2007-11-07)
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.
Nowadays, selected stars are photographed at appropriate atomic times as they transit the local zenith determined via telescopes using a pool of mercury as a mirror (photographic zenith tubes).
The error between the photographed transit and the calculated transit is used to determine whether a leap second is needed to keep Coordinated Universal Time (UTC) within 0.9 seconds of Greenwich Mean Time, mean solar time at Greenwich, England.
open-encyclopedia.com /Solar_time   (580 words)

  
 Stanford Solar Center   (Site not responding. Last check: 2007-11-07)
The solar corona material is massive in size (they can occupy up to a quarter of the solar limb), and frequently accompanied by the remnants of an eruptive prominence, and less often by a strong solar flare.
Sunspots and faculae are observed in the photosphere.
The earlier spots in the solar cycle appear at higher latitudes and the later spots in the solar cycle emerge nearer to the equator.
solar-center.stanford.edu /gloss.html   (2697 words)

  
 Time zone article - Time zone Time Zone Earth time solar time town telecommunications railways - What-Means.com   (Site not responding. Last check: 2007-11-07)
Time zones partially rectified the problem by setting the clocks of a region to the same mean solar time.
Time zones are generally centered on meridians of a longitude that is a multiple of 15° thus making neighbouring time zones one hour apart.
Time zones were first proposed for the entire world by Sir Sandford Fleming in 1876 as an appendage to the single 24-hour clock he proposed for the entire world (located at the center of the Earth and not linked to any surface meridian!).
www.what-means.com /encyclopedia/Time_zone   (2078 words)

  
 Time   (Site not responding. Last check: 2007-11-07)
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)

  
 The Time of Internet - Solar Time   (Site not responding. Last check: 2007-11-07)
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)

  
 History & info - Standard time began with the railroads
Standard time in the US Standard time in time zones was instituted in the U.S. and Canada by the railroads on 18 November 1883.
Before then, time of day was a local matter, and most cities and towns used some form of local solar time, maintained by some well-known clock (for example, on a church steeple or in a jeweler's window).
Time zones were first used by the railroads in 1883 to standardize their schedules.
webexhibits.org /daylightsaving/d.html   (1044 words)

  
 Timekeeping
Technically, the sidereal time is defined as the length of time since the vernal equinox has crossed the local celestial meridian.
To be precise, the sidereal time agrees with the solar time only at the autumnal equinox; at any other time, they differ (they are exactly 12 hours apart at the time of the vernal equinox).
It is this almost 4 minute per day discrepancy that causes the difference in sidereal and solar time, and is responsible for the fact that different constellations are everhead at a given time of day during the Summer than in the Winter.
csep10.phys.utk.edu /astr161/lect/time/timekeeping.html   (465 words)

  
 TIME INTERNATIONAL: Solar Power Players --PAGE 1-- October 5, 1998
BP Solar currently sits in fourth place with 10%, but the creation of BP Amoco, though not a fait accompli, is forcing the solar industry to view its combined market share at around 23%--or the new Number One.
BP Solar leans more toward packaged systems based on its PV modules and tends to bypass distributors to work directly with dealers; Solarex is more technology-based with a strong distributor-dealer network, demanding less in-house support.
But before the betrothed companies marry their solar assets and cash in on the added value, they face the Enron question: BP and Amoco's merger is not a straightforward marriage for the solar sector; it's a love triangle.
time.com /time/magazine/1998/int/981005/business.solar_power_pl19a.html   (640 words)

  
 Technical Notes on Mars Solar Time   (Site not responding. Last check: 2007-11-07)
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.
Predicted solar times for a given lander location may therefore need to be revised post-touchdown as improved navigation for their coordinates becomes available.
www.giss.nasa.gov /tools/mars24/help/notes.html   (2462 words)

  
 Time Scales
The mean solar time of Greenwich attained a unique distinction at the International Meridian Conference held in Washington during October.
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   (12077 words)

  
 Eclipse Filters
A total solar eclipse is probably the most spectacular astronomical event that most people will experience in their lives.
Solar radiation reaching the surface of the earth ranges from ultraviolet (UV) radiation at wavelengths longer than 290 nm to radio waves in the metre range.
It is widely accepted that environmental exposure to high levels of solar UV radiation contributes to the accelerated ageing of the outer layers of the eye and skin, and the development of cataracts.
www.mreclipse.com /Special/filters.html   (2271 words)

  
 Astronomical Times
Several important time scales still follow the rotation of the earth, most notably civil and sidereal time, but of these are now derived from atomic time through a combination of earth rotation theory and actual measurements of the earth's rotation and orientation.
By convention, the reference points for Greenwich Sidereal Time are the Greenwich Meridian and the vernal equinox (the intersection of the planes of the earth's equator and the earth's orbit, the ecliptic).
It might seem strange that UT1, a solar time, is determined by measuring the earth's rotation with respect to distant celestial objects, and GMST, a sidereal time, is derived from it.
www.cv.nrao.edu /~rfisher/Ephemerides/times.html   (2060 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)

  
 Stanford SOLAR Center -- Ask A Solar Physicist FAQs - Answer   (Site not responding. Last check: 2007-11-07)
Before there were accurate clocks, noon meant "high noon": the time when the Sun was due south or highest in the sky (which is practically the same thing).
Because the apparent speed of the Sun in the sky is faster in December than in June, the southern (September to March) part of the analemma is wider than the northern (March to September) part.
The analemma is 47 degrees long (two times the obliquity of the ecliptic) and, at its widest part, about 8 degrees wide.
solar-center.stanford.edu /FAQ/Qsunaspattern.html   (564 words)

  
 NASA GISS: Science Briefs: Telling Time on Mars   (Site not responding. Last check: 2007-11-07)
Accurate solar time keeping on Mars is essential to the study of its weather and climate.
But accurate solar time keeping on Mars is further complicated by the planet's orbital eccentricity, over five times larger than Earth's, implying a nearly 40% seasonal variation in its incoming sunlight and a fifty minute variation in the timing of local noon (as measured on a 24 "hour" Mars clock).
I have built this new solar timing method into a Mars-adapted version of the GISS general circulation model as a further step in my work toward the development of a weather mapping program for the upcoming Surveyor 98 mission to Mars.
www.giss.nasa.gov /research/briefs/allison_02   (463 words)

  
 The Resurgent Sun
Says David Hathaway, a solar physicist at the NASA Marshall Space Flight Center: "The current solar cycle appears to be double-peaked," and the second peak has arrived.
Solar Max eleven years ago was much the same.
Hathaway notes a widespread misconception that solar activity varies every 11 years "like a pure sinusoid." In fact, he says, solar activity is chaotic; there is more than one period.
science.nasa.gov /headlines/y2002/18jan_solarback.htm   (1266 words)

  
 Technical Notes on Mars Solar Time   (Site not responding. Last check: 2007-11-07)
A less technical account of solar time on Mars is provided in the article Telling Time on Mars on the NASA GISS website.
Mars24 estimates of times of local sunrise and sunset will be affected by local topography, as well as atmospheric refraction, and may be in error by as much as 2 minutes.
August 2003: The conversion between the terrestrial time TT and Universal Coordinated Time UTC as given by Equation 27 of AM2000 was modified for greater accuracy with a fourth-order polynomial representation, accurate to within 3sec for 1975-2005.
www.gps.caltech.edu /~shealy/mars24j/help/notes.html   (2176 words)

  
 Sidereal Time   (Site not responding. Last check: 2007-11-07)
Sidereal time is time kept with respect to the distant stars.
A solar day lasts from when the Sun is on the meridian at a point on Earth until it is next on the meridian.
A solar day is exactly 24 hours (of solar time).
astrosun2.astro.cornell.edu /academics/courses/astro201/sidereal.htm   (276 words)

  
 The Hutchinson Encyclopedia: solar time@ HighBeam Research   (Site not responding. Last check: 2007-11-07)
Time of day as determined by the position of the Sun in the sky.
Apparent solar time, the time given by a sundial, is not uniform because of the varying speed of the Earth in its elliptical orbit.
Mean solar time is a uniform time that coincides with apparent solar time at four instants through the year.
www.highbeam.com /library/doc0.asp?DOCID=1P1:100177406   (138 words)

  
 Complete Sun and Moon Data for One Day   (Site not responding. Last check: 2007-11-07)
For U.S. cities or towns (Form A), the times of the phenomena are presented in the standard time of the place requested, using the current time zone of the place.
Standard time in time zones was introduced in the U.S. in 1883, but the time zone boundaries have evolved considerably since then, with places shifting from one zone to another.
Daylight time is implemented only for U.S. cities or towns (Form A) and only for years 1967 and later, in accordance with the Uniform Time Act of 1966 and subsequent legislation.
aa.usno.navy.mil /data/docs/RS_OneDay.html   (745 words)

  
 Solar Time   (Site not responding. Last check: 2007-11-07)
The apparent motion of the sun across the sky has long been used as a basis for measuring time.
The length of the day according to solar time is not the same throughout the year, however, because the apparent motion of the sun varies throughout the year.
Mean solar time was invented, based on the motion of a hypothetical sun traveling at an even rate throughout the year.
www.skybooksusa.com /time-travel/timeinfo/solar.htm   (150 words)

  
 [sci.astro] Time (Astronomy Frequently Asked Questions) (3/9)
SIDEREAL TIME: Closely connected with the Mean Solar Time is the Sidereal Time, which is defined as the RA (Right Ascension) of the Local Meridian: when the Vernal Point passes the meridian it is 00:00 Sidereal Time.
The Sidereal Time at a particular place and location is the same as the local Mean Solar Time, plus 12 hours, plus the Right Ascension of the Mean Sun (which is the same as the Mean Longitude of the true sun).
At first the time to be used within a country was the local time of the capital of the country.
www.faqs.org /faqs/astronomy/faq/part3   (7327 words)

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