Synodic day

Synodic day

A synodic day is the period of time it takes for a planet to rotate once in relation to the body it is orbiting (as opposed to a sidereal day which is one complete rotation in relation to the stars).

Thus, a synodic day can be thought as 'sunrise to sunrise', whereas a sidereal day would be 'star-rise to star-rise'. These two quantities are not equal because the sun, as seen from earth, moves against the fixed sphere of stars along an imaginary line known as the ecliptic. The sun moves a little less than a degree each day -- (360 degrees/year)/(365.25 days/year) -- in East to West fashion known as prograde motion.

Although this thinking is correct, in a sense, neither term can be defined rising or setting of a celestial body because of variations due to the earth's tilt. See Equation of time.

For Earth, the Synodic day is known as a Solar day, and is 24hrs long.

ee also

* solar time
* synodic month
* synodic period
* Solar rotation
* Sidereal year

Wikimedia Foundation. 2010.

Игры ⚽ Поможем написать курсовую

Look at other dictionaries:

  • Day — For other uses, see Day (disambiguation). Water, Rabbit, and Deer: three of the 20 day symbols in the Aztec calendar, from the Aztec calendar stone. A day is a unit of time, commonly defined as an interval equal to 24 hours …   Wikipedia

  • Lunar day — In space exploration, a lunar day is the period of time it takes for the Moon to complete one full rotation on its axis with respect to the Sun . Equivalently, it is the time it takes the Moon to make one complete orbit around the Earth and come… …   Wikipedia

  • Analemma — was also a book by Ptolemy .In astronomy, an analemma (IPA: IPA|/ˌænəˈlɛmə/, Latin for the pedestal of a sundial) is a curve representing the angular offset of a celestial body (usually the Sun) from its mean position on the celestial sphere as… …   Wikipedia

  • Solar time — 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 …   Wikipedia

  • Full moon cycle — The full moon cycle is a cycle of about 14 lunations over which full moons vary in apparent size and age (time since new moon). The sequence is *Full moon big (perigee at full moon) *Full moon young (perigee at first quarter) *Full moon small… …   Wikipedia

  • Hebrew calendar — The Hebrew calendar (הלוח העברי ha luach ha ivri), or Jewish calendar, is a lunisolar calendar used today predominantly for Jewish religious observances. It determines the dates for Jewish holidays and the appropriate public reading of Torah… …   Wikipedia

  • Month — For the Egyptian hawk god, see Monthu. A month is a unit of time, used with calendars, which was first used and invented in Mesopotamia, as a natural period related to the motion of the Moon; month and Moon are cognates. The traditional concept… …   Wikipedia

  • calendar — calendrical /keuh len dri keuhl/, calendric, calendarial /kal euhn dair ee euhl/, calendarian, calendaric, adj. /kal euhn deuhr/, n. 1. a table or register with the days of each month and week in a year: He marked the date on his calendar. 2. any …   Universalium

  • Eclipse cycle — Animated graph of a the paths of totality of a solar eclipse cycle. Eclipses may occur repeatedly, separated by certain intervals of time: these intervals are called eclipse cycles.[1] The series of eclipses separated by a repeat of one of these… …   Wikipedia

  • Hindu chronology — The subject of Hindu chronology divides naturally into three parts: the calendar, the eras, and other reckonings. The Calendar The Hindus have had, from very ancient times, the system of lunisolar cycles, made by the combination of solar years,… …   Wikipedia

Share the article and excerpts

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