Sidereal Days Compared To Solar Days On Other Planets
Of the eight solar planets, all but Venus and Uranus have prograde rotation—that is, they rotate more than once per year in the same direction as they orbit the sun, so the sun rises in the east. Venus and Uranus, however, have retrograde rotation. For prograde rotation, the formula relating the lengths of the sidereal and solar days is
or equivalently
On the other hand, the formula in the case of retrograde rotation is
or equivalently
All the solar planets more distant from the sun than Earth are similar to Earth in that, since they experience many rotations per revolution around the sun, there is only a small difference between the length of the sidereal day and that of the solar day—the ratio of the former to the latter never being less than Earth's ratio of .997 . But the situation is quite different for Mercury and Venus. Mercury's sidereal day is about two-thirds of its orbital period, so by the prograde formula its solar day lasts for two revolutions around the sun—three times as long as its sidereal day. Venus rotates retrograde with a sidereal day lasting about 243.0 earth-days, or about 1.08 times its orbital period of 224.7 earth-days; hence by the retrograde formula its solar day is about 116.8 earth-days, and it has about 1.9 solar days per orbital period.
By convention, rotation periods of planets are given in sidereal terms unless otherwise specified.
Read more about this topic: Sidereal Time
Famous quotes containing the words sidereal, days, compared, solar and/or planets:
“Perhaps our eyes are merely a blank film which is taken from us after our deaths to be developed elsewhere and screened as our life story in some infernal cinema or despatched as microfilm into the sidereal void.”
—Jean Baudrillard (b. 1929)
“Take two pounds of meat from the rump, boil three days in a deep kettle with the head of an axe, and, then, throw away the meat and eat the axe.”
—State of Utah, U.S. public relief program (1935-1943)
“The fact is popular art dates. It grows quaint. How many people feel strongly about Gilbert and Sullivan today compared to those who felt strongly in 1890?”
—Stephen Sondheim (b. 1930)
“Lincoln becomes the American solar myth, the chief butt of American credulity and sentimentality.”
—H.L. (Henry Lewis)
“Perhaps when distant people on other planets pick up some wave-length of ours all they hear is a continuous scream.”
—Iris Murdoch (b. 1919)