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  2. Sidereal time - Wikipedia

    en.wikipedia.org/wiki/Sidereal_time

    A year has about 365.24 solar days but 366.24 sidereal days. Therefore, there is one fewer solar day per year than there are sidereal days, similar to an observation of the coin rotation paradox. [5] This makes a sidereal day approximately ⁠ 365.24 / 366.24 ⁠ times the length of the 24-hour solar day.

  3. Unit of time - Wikipedia

    en.wikipedia.org/wiki/Unit_of_time

    For example, the year cannot be divided into twelve 28-day months since 12 times 28 is 336, well short of 365. The lunar month (as defined by the moon's rotation) is not 28 days but 28.3 days. The year, defined in the Gregorian calendar as 365.2425 days has to be adjusted with leap days and leap seconds. Consequently, these units are now all ...

  4. Hindu units of time - Wikipedia

    en.wikipedia.org/wiki/Hindu_units_of_time

    12 hours (1 day proper: kalpa) of Brahma = 4.32 billion solar years (1,000 chatur-yugas; 14 manvantaras + 15 manvantara-sandhyas) 24 hours (1 day & night: kalpa + pralaya) of Brahma = 8.64 billion solar years; 30 days (1 month) of Brahma = 259.2 billion solar years; 12 months (1 year) of Brahma = 3.1104 trillion solar years

  5. Day - Wikipedia

    en.wikipedia.org/wiki/Day

    A sidereal day or stellar day is the span of time it takes for the Earth to make one entire rotation [5] with respect to the celestial background or a distant star (assumed to be fixed). [6] Measuring a day as such is used in astronomy. [6] A sidereal day is about 4 minutes less than a solar day of 24 hours (23 hours 56 minutes and 4.09 seconds ...

  6. Coin rotation paradox - Wikipedia

    en.wikipedia.org/wiki/Coin_rotation_paradox

    The paradox is related to sidereal time: a sidereal day is the time Earth takes to rotate for a distant star to return to the same position in the sky, whereas a solar day is the time for the sun to return to the same position. A year has around 365.25 solar days, but 366.25 sidereal days to account for one revolution around the sun. [6]

  7. Rotation period (astronomy) - Wikipedia

    en.wikipedia.org/wiki/Rotation_period_(astronomy)

    58.6462 days [3] 58 d 15 h 30 m 30 s: 176 days [4] Venus: −243.0226 days [ii] [5] −243 d 0 h 33 m: −116.75 days [6] Earth: 0.99726968 days [3] [iii] 0 d 23 h 56 m 4.0910 s: 1.00 days (24 h 00 m 00 s) Moon: 27.321661 days [7] (equal to sidereal orbital period due to spin-orbit locking, a sidereal lunar month) 27 d 7 h 43 m 11.5 s: 29. ...

  8. Sidereal year - Wikipedia

    en.wikipedia.org/wiki/Sidereal_year

    The sidereal year is 20 min 24.5 s longer than the mean tropical year at J2000.0 (365.242 190 402 ephemeris days). [ 1 ] At present, the rate of axial precession corresponds to a period of 25,772 years, [ 3 ] so sidereal year is longer than tropical year by 1,224.5 seconds (20 min 24.5 s, ~365.24219*86400/25772).

  9. Time standard - Wikipedia

    en.wikipedia.org/wiki/Time_standard

    A mean solar day is about 3 minutes 56 seconds longer than a mean sidereal day, or 1 ⁄ 366 more than a mean sidereal day. In astronomy, sidereal time is used to predict when a star will reach its highest point in the sky. For accurate astronomical work on land, it was usual to observe sidereal time rather than solar time to measure mean solar ...