Patek Philippe - Caliber 89 Solar Time

Channel: WatchesOnTime   |   2012/12/08
Play Video
1
Patek Philippe - Caliber 89 Solar Time
Patek Philippe - Caliber 89 Solar Time
::2012/12/08::
Play Video
2
Astronomy 101:  Solar vs. Sidereal Time
Astronomy 101: Solar vs. Sidereal Time
::2012/10/02::
Play Video
3
North Star Calendar Earth Time System - Solar Time System - Universal Time System - Part 1 [HQ]
North Star Calendar Earth Time System - Solar Time System - Universal Time System - Part 1 [HQ]
::2013/01/23::
Play Video
4
Solar Time Calculator
Solar Time Calculator
::2012/05/31::
Play Video
5
Honeywell Econoswitch RPLS740B 7 Day Solar Time Table Programmable Switch Review!
Honeywell Econoswitch RPLS740B 7 Day Solar Time Table Programmable Switch Review!
::2014/02/14::
Play Video
6
Solar Time Lapse Video Crystalline Solar Panel vs. PowerFilm
Solar Time Lapse Video Crystalline Solar Panel vs. PowerFilm
::2012/08/07::
Play Video
7
Solar Time Lapse Installation Video, Jeff Stone HERO, HelioPower
Solar Time Lapse Installation Video, Jeff Stone HERO, HelioPower
::2012/06/22::
Play Video
8
الساعة الشمسية Solar time
الساعة الشمسية Solar time
::2013/10/10::
Play Video
9
Honeywell Econoswitch RPLS740B 7-Day Solar Time Table Programmable Switch
Honeywell Econoswitch RPLS740B 7-Day Solar Time Table Programmable Switch
::2013/02/28::
Play Video
10
Solar time distortion experiment.
Solar time distortion experiment.
::2012/07/22::
Play Video
11
CSU Solar Time lapse
CSU Solar Time lapse
::2012/09/04::
Play Video
12
Ecolibrium Solar Time Lapse
Ecolibrium Solar Time Lapse
::2013/02/21::
Play Video
13
EST (ephemeris solar time)
EST (ephemeris solar time)
::2013/11/18::
Play Video
14
SOLAR TIME-LAPSE Video - March 3, 2014: Solar Flare & Highlights of Activity from The SUN in HD
SOLAR TIME-LAPSE Video - March 3, 2014: Solar Flare & Highlights of Activity from The SUN in HD
::2014/03/04::
Play Video
15
Berkley East Solar Time Lapse
Berkley East Solar Time Lapse
::2013/11/04::
Play Video
16
Solar time lapse
Solar time lapse
::2013/03/15::
Play Video
17
SOLAR TIME-LAPSE Video: M1.1 Solar Flare & Daily Highlights from The SUN [HD] February 26, 2014
SOLAR TIME-LAPSE Video: M1.1 Solar Flare & Daily Highlights from The SUN [HD] February 26, 2014
::2014/02/27::
Play Video
18
Solar Time-Lapse
Solar Time-Lapse
::2012/02/16::
Play Video
19
SOLAR TIME-LAPSE Video: March 13, 2014: The Past 72 hours on The Sun in HD
SOLAR TIME-LAPSE Video: March 13, 2014: The Past 72 hours on The Sun in HD
::2014/03/13::
Play Video
20
Piedmont Biofuels Solar Time Lapse
Piedmont Biofuels Solar Time Lapse
::2011/10/21::
Play Video
21
SEIKO GPS Solar / Time Zone Adjustment - Infographics movie
SEIKO GPS Solar / Time Zone Adjustment - Infographics movie
::2014/03/04::
Play Video
22
Apparent Solar Day and Sidereal Time
Apparent Solar Day and Sidereal Time
::2013/08/24::
Play Video
23
Sunpower Solar Time-Lapse
Sunpower Solar Time-Lapse
::2013/08/07::
Play Video
24
Sinclair Harding Giant Carriage Clock, Chronometer Escapement, Moon Phase, Calendars, Solar Time!
Sinclair Harding Giant Carriage Clock, Chronometer Escapement, Moon Phase, Calendars, Solar Time!
::2013/02/16::
Play Video
25
SOLAR TIME-LAPSE Video: HUGE X4.9 Solar Flare & Daily Highlights from The SUN [HD] February 25, 2014
SOLAR TIME-LAPSE Video: HUGE X4.9 Solar Flare & Daily Highlights from The SUN [HD] February 25, 2014
::2014/02/25::
Play Video
26
SOLAR TIME-LAPSE: February 24, 2014 - The sun in HD as it was from the past 24 hours.
SOLAR TIME-LAPSE: February 24, 2014 - The sun in HD as it was from the past 24 hours.
::2014/02/24::
Play Video
27
FTB Unleashed Ep:34 Solar Time
FTB Unleashed Ep:34 Solar Time
::2013/10/21::
Play Video
28
THiNKnrg - JCC Solar Time Laspe
THiNKnrg - JCC Solar Time Laspe
::2014/03/24::
Play Video
29
SOLAR TIME-LAPSE Video - March 8, 2014: Dancing Plasma, Dark Filaments & The SUN in HD
SOLAR TIME-LAPSE Video - March 8, 2014: Dancing Plasma, Dark Filaments & The SUN in HD
::2014/03/09::
Play Video
30
Solar/Białas - Olejmy Jutro 2 (Time Of Your Life RMX)
Solar/Białas - Olejmy Jutro 2 (Time Of Your Life RMX)
::2012/06/09::
Play Video
31
Solar Fields~ Time Slide
Solar Fields~ Time Slide
::2010/03/01::
Play Video
32
SOLAR TIME-LAPSE Video - March 9, 2014: M-Class Solar Flares & The SUN in HD
SOLAR TIME-LAPSE Video - March 9, 2014: M-Class Solar Flares & The SUN in HD
::2014/03/10::
Play Video
33
SOLAR TIME-LAPSE Video - March 5, 2014: Filament Eruption, Polar Plasma & The SUN in HD
SOLAR TIME-LAPSE Video - March 5, 2014: Filament Eruption, Polar Plasma & The SUN in HD
::2014/03/06::
Play Video
34
Oak Grove Plantation B&B Solar Time Lapse
Oak Grove Plantation B&B Solar Time Lapse
::2012/12/17::
Play Video
35
SOLAR TIME-LAPSE Video: M-Class Flare, Far-Side CME & Highlights from The SUN in HD - March 1, 2014
SOLAR TIME-LAPSE Video: M-Class Flare, Far-Side CME & Highlights from The SUN in HD - March 1, 2014
::2014/03/01::
Play Video
36
Davidson College Solar Time Lapse
Davidson College Solar Time Lapse
::2012/03/15::
Play Video
37
Deanwood Solar TIme Bank - 3
Deanwood Solar TIme Bank - 3
::2011/03/14::
Play Video
38
Solar Time Calculator App by ATP
Solar Time Calculator App by ATP
::2014/03/11::
Play Video
39
Sterling Solar Time Lapse
Sterling Solar Time Lapse
::2013/11/04::
Play Video
40
Solar Time lapse; May 20th - July 8th 2010
Solar Time lapse; May 20th - July 8th 2010
::2010/07/12::
Play Video
41
My failed suburban night ryde part 2 of 2 (polar/solar time)
My failed suburban night ryde part 2 of 2 (polar/solar time)
::2010/10/21::
Play Video
42
Tindo Solar Time Lapse
Tindo Solar Time Lapse
::2012/01/25::
Play Video
43
Sinclair Harding Carriage Clock,Chronometer Escapement,Moon Phase,Calendars,Solar Time!Part 2 (SOLD)
Sinclair Harding Carriage Clock,Chronometer Escapement,Moon Phase,Calendars,Solar Time!Part 2 (SOLD)
::2013/02/17::
Play Video
44
Bergelectric Carport Solar Time Lapse
Bergelectric Carport Solar Time Lapse
::2013/08/30::
Play Video
45
100 solar time periods
100 solar time periods
::2012/03/01::
Play Video
46
SOLAR TIME-LAPSE Video: Daily Highlights from The SUN in HD - February 27, 2014
SOLAR TIME-LAPSE Video: Daily Highlights from The SUN in HD - February 27, 2014
::2014/02/28::
Play Video
47
Thermal Solar
Thermal Solar's Time to Shine
::2008/06/20::
Play Video
48
TRUE SOLAR TIME  MULTI PURPOSE ALUMINIUM SOLAR PANEL RAIL AND TILT FRAME COMPLETE
TRUE SOLAR TIME MULTI PURPOSE ALUMINIUM SOLAR PANEL RAIL AND TILT FRAME COMPLETE
::2011/10/10::
Play Video
49
The Leap Year Bug (updated 4.10.2012) - Earth Time System - Solar Time System
The Leap Year Bug (updated 4.10.2012) - Earth Time System - Solar Time System
::2012/04/10::
Play Video
50
The Solar Time Temple ダイジェスト
The Solar Time Temple ダイジェスト
::2013/02/17::
NEXT >>
RESULTS [51 .. 101]
From Wikipedia, the free encyclopedia
  (Redirected from Apparent solar time)
Jump to: navigation, search
On a prograde planet like the Earth, the sidereal day is shorter than the solar day. At time 1, the Sun and a certain distant star are both overhead. At time 2, the planet has rotated 360° and the distant star is overhead again (1→2 = one sidereal day). But it is not until a little later, at time 3, that the Sun is overhead again (1→3 = one solar day). More simply, 1-2 is a complete rotation of the Earth, but because the revolution around the Sun affects the angle at which the Sun is seen from the Earth, 1-3 is how long it takes noon to return.

Solar time is a reckoning of the passage of time based on the Sun's position in the sky. The fundamental unit of solar time is the day. Two types of solar time are apparent solar time (sundial time) and mean solar time (clock time).

Introduction[edit]

Fix a tall pole vertically in the ground; at some instant on any sunny day the shadow will point exactly north or south (or disappear, if the Sun is directly overhead). That instant is local apparent noon: 12:00 local apparent time. About 24 hours later the shadow will again point north/south, the Sun seeming to have covered a 360-degree arc around the Earth's axis. When the Sun has covered exactly 15 degrees (1/24 of a circle, both angles being measured in a plane perpendicular to the Earth's axis), local apparent time is 13:00 exactly; after 15 more degrees it will be 14:00 exactly.

The problem is that in September the Sun takes less time (as measured by an accurate clock) to make an apparent revolution than it does in December; 24 "hours" of solar time can be 21 seconds less or 29 seconds more than 24 hours of clock time. As explained in the equation of time article, this is due to the ellipticity of the Earth's orbit and the fact that the Earth's axis is not perpendicular to the plane of its orbit.

So a clock that runs at a constant rate — the same number of pendulum swings in each hour — cannot follow the actual Sun; instead it follows an imaginary "mean Sun" that moves along the celestial equator at a constant rate that matches the real Sun's average rate over the year.[1] This is "mean solar time", which is still not perfectly constant from one century to the next but is close enough for most purposes. Currently a mean solar day is about 86,400.002 SI seconds.[2]

The two kinds of solar time (apparent solar time and mean solar time) are among the three kinds of time reckoning that were employed by astronomers until the 1950s. (The third kind of traditional time reckoning is sidereal time, which is based on the apparent motions of stars other than the Sun.)[3] By the 1950s it had become clear that the Earth's rotation rate was not constant, so astronomers developed ephemeris time, a time scale based on the positions of solar system bodies in their orbits.

Apparent solar time[edit]

Apparent solar time or true solar time is based on the apparent motion of the actual Sun. It is based on the apparent solar day, the interval between two successive returns of the Sun to the local meridian.[4][5] Solar time can be crudely measured by a sundial.

The length of a solar day varies through the year, and the accumulated effect produces seasonal deviations of up to 16 minutes from the mean. The effect has two main causes. First, Earth's orbit is an ellipse, not a circle, so the Earth moves faster when it is nearest the Sun (perihelion) and slower when it is farthest from the Sun (aphelion) (see Kepler's laws of planetary motion). Second, due to Earth's axial tilt (known as the obliquity of the ecliptic), the Sun's annual motion is along a great circle (the ecliptic) that is tilted to Earth's celestial equator. When the Sun crosses the equator at both equinoxes, the Sun's daily shift (relative to the background stars) is at an angle to the equator, so the projection of this shift onto the equator is less than its average for the year; when the Sun is farthest from the equator at both solstices, the Sun's shift in position from one day to the next is parallel to the equator, so the projection onto the equator of this shift is larger than the average for the year (see tropical year). Also, in June and December when the sun is farthest from the celestial equator a given shift along the ecliptic corresponds to a larger shift on the equator. So apparent solar days are shorter in March and September than in June or December.

Length of apparent solar day (1998)[6]
Date Duration in mean solar time
February 11 24 hours
March 26 24 hours − 18.1 seconds
May 14 24 hours
June 19 24 hours + 13.1 seconds
July 26 24 hours
September 16 24 hours − 21.3 seconds
November 3 24 hours
December 22 24 hours + 29.9 seconds

These lengths will change slightly in a few years and significantly in thousands of years.

Mean solar time[edit]

The equation of time—above the axis a sundial will appear fast relative to a clock showing local mean time, and below the axis a sundial will appear slow.

Mean solar time is the hour angle of the mean Sun plus 12 hours. Currently (2009) this is realized with the UT1 time scale, constructed mathematically from very long baseline interferometry observations of the diurnal motions of radio sources located in other galaxies, and other observations.[7][8] The duration of daylight varies during the year but the length of a mean solar day is nearly constant, unlike that of an apparent solar day.[9] An apparent solar day can be 20 seconds shorter or 30 seconds longer than a mean solar day.[6][10] Long or short days occur in succession, so the difference builds up until mean time is ahead of apparent time by about 14 minutes near February 6 and behind apparent time by about 16 minutes near November 3. The equation of time is this difference, which is cyclical and does not accumulate from year to year.

Mean time follows the "mean sun", best described by Meeus:

"Consider a first fictitious Sun travelling along the ecliptic with a constant speed and coinciding with the true sun at the perigee and apogee (when the Earth is in perihelion and aphelion, respectively). Then consider a second fictitious Sun travelling along the celestial equator at a constant speed and coinciding with the first fictitious Sun at the equinoxes. This second fictitious sun is the mean Sun..."[11]

The length of the mean solar day is slowly increasing due to the tidal acceleration of the Moon by the Earth and the corresponding slowing of Earth's rotation by the Moon.

History[edit]

Many methods have been used to simulate mean solar time. The earliest were clepsydras or water clocks, used for almost four millennia from as early as the middle of the 2nd millennium BC until the early 2nd millennium. Before the middle of the 1st millennium BC, the water clocks were only adjusted to agree with the apparent solar day, thus were no better than the shadow cast by a gnomon (a vertical pole), except that they could be used at night.

But it has long been known that the Sun moves eastward relative to the fixed stars along the ecliptic. Since the middle of the first millennium BC the diurnal rotation of the fixed stars has been used to determine mean solar time, against which clocks were compared to determine their error rate. Babylonian astronomers knew of the equation of time and were correcting for it as well as the different rotation rate of the stars, sidereal time, to obtain a mean solar time much more accurate than their water clocks. This ideal mean solar time has been used ever since then to describe the motions of the planets, Moon, and Sun.

Mechanical clocks did not achieve the accuracy of Earth's "star clock" until the beginning of the 20th century. Today's atomic clocks have a much more constant rate than the Earth, but its star clock is still used to determine mean solar time. Since sometime in the late 20th century, Earth's rotation has been defined relative to an ensemble of extra-galactic radio sources and then converted to mean solar time by an adopted ratio. The difference between this calculated mean solar time and Coordinated Universal Time (UTC) determines whether a leap second is needed. (The UTC time scale now runs on SI seconds, and the SI second, when adopted, was already a little shorter than the current value of the second of mean solar time.[12])

See also[edit]

References[edit]

  1. ^ Astronomical Almanac Online. (2011) Her Majesty's Nautical Almanac Office and the United States Naval Observatory. Glossary s.v. solar time.
  2. ^ Leap Seconds. (1999). Time Service Department, United States Naval Observatory.
  3. ^ For the three kinds of time, see (for example) the explanatory section in the almanac Connaissance des Temps for 1902, page 759.
  4. ^ Astronomical Almanac Online (2010). United States Naval Observatory. s.v. solar time, apparent; diurnal motion; apparent place.
  5. ^ Yallop, B. D. and Hohenkerk, C. Y. (August 1989). Solar Location Diagram (Astronomical Information Sheet No. 58). HM Nautical Almanac Office.
  6. ^ a b Jean Meeus (1997), Mathematical astronomy morsels (Richmond, VA: Willmann-Bell) 346. ISBN 0-943396-51-4.
  7. ^ McCarthy, D. D. & Seidelmann, P. K. (2009). TIME From Earth Rotation to Atomic Physics. Weinheim: Wiley-VCH Verlag GmbH & Co. KGaA. ISBN 978-3-527-40780-4. pp. 68, 326.
  8. ^ Capitaine, N., Wallace, P. T., & McCarthy, D. D. (2003). "Expressions to implement the IAU 2000 definition of UT1", Astronomy and Astrophysics, vol.406 (2003), pp.1135-1149 (or in pdf form); and for some earlier definitions of UT1 see Aoki, S., H Kinoshita, H., Guinot, B., Kaplan, G. H., D D McCarthy, D. D., & Seidelmann, P. K. (1982) "The new definition of universal time", Astronomy and Astrophysics, vol.105 (1982), pp.359-361.
  9. ^ For a discussion of the slight changes that affect the mean solar day, see the ΔT article.
  10. ^ "The duration of the true solar day". Pierpaolo Ricci. pierpaoloricci.it. (Italy)
  11. ^ Meeus, J. (1998). Astronomical Algorithms. 2nd ed. Richmond VA: Willmann-Bell. p. 183.
  12. ^ :(1) In "The Physical Basis of the Leap Second", by D D McCarthy, C Hackman and R A Nelson, in Astronomical Journal, vol.136 (2008), pages 1906-1908, it is stated (page 1908), that "the SI second is equivalent to an older measure of the second of UT1, which was too small to start with and further, as the duration of the UT1 second increases, the discrepancy widens." :(2) In the late 1950s, the cesium standard was used to measure both the current mean length of the second of mean solar time (UT2) (result: 9192631830 cycles) and also the second of ephemeris time (ET) (result:9192631770 +/-20 cycles), see "Time Scales", by L. Essen, in Metrologia, vol.4 (1968), pp.161-165, on p.162. As is well known, the 9192631770 figure was chosen for the SI second. L Essen in the same 1968 article (p.162) stated that this "seemed reasonable in view of the variations in UT2".

External links[edit]

Wikipedia content is licensed under the GFDL License

Mashpedia enables any individual or company to promote their own Youtube-hosted videos or Youtube Channels, offering a simple and effective plan to get them in front of our engaged audience.

Want to learn more? Please contact us at: hello@mashpedia.com

Powered by YouTube
LEGAL
  • Mashpedia © 2014