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This is due to the solar day being shorter than the sidereal day for retrograde rotation, as the rotation of the planet would be against the direction of orbital motion. If a planet rotates prograde, and the sidereal day exactly equals the orbital period, then the formula above gives an infinitely long solar day (division by zero).
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 ...
A synodic day (or synodic rotation period or solar day) is the period for a celestial object to rotate once in relation to the star it is orbiting, and is the basis of solar time. The synodic day is distinguished from the sidereal day, which is one complete rotation in relation to distant stars [1] and is the basis of sidereal time. In the case ...
Rotation period with respect to distant stars, the sidereal rotation period (compared to Earth's mean Solar days) Synodic rotation period (mean Solar day) Apparent rotational period viewed from Earth Sun [i] 25.379995 days (Carrington rotation) 35 days (high latitude) 25 d 9 h 7 m 11.6 s 35 d ~28 days (equatorial) [2] Mercury: 58.6462 days [3 ...
A sidereal day is about 4 minutes less than a solar day of 24 hours (23 hours 56 minutes and 4.09 seconds), or 0.99726968 of a solar day of 24 hours. [7] There are about 366.2422 stellar days in one mean tropical year (one stellar day more than the number of solar days). [8]
The average of the true solar day during the course of an entire year is the mean solar day, which contains 86,400 mean solar seconds. Currently, each of these seconds is slightly longer than an SI second because Earth's mean solar day is now slightly longer than it was during the 19th century due to tidal friction. The average length of the ...
Known affectionately to scientists as the "boring billion," there was a seemingly endless period in the world's history when the length of a day stayed put. The time when a day on Earth was just ...
The exact length has been variously defined as either that of a solar day or of a sidereal day. [1] [2] [3] Astronomical days were historically used by astronomers (in contrast most commonly to solar days), but since the Industrial Revolution this usage has generally fallen out of favor, in order to avoid confusion with more conventional ...