MargaritaMc wrote:I have read what Wikipedia says but just cannot ' get it. :bang:
I understand (I think) what is meant by a Synodical Month, as in from New Moon to New Moon. But I just do not understand why, say, the synodic period of Saturn is 378 days although its orbital period is more than 29 years. And, according to Wikipedia, the synodic period of Mars is 779 days - more than Saturn's...
Is there any kind soul out there who would like to attempt to enlighten me?
The (sidereal) orbital period of any body is simply the time it takes to complete one orbit, relative to the stars. That period depends on the distance of the body from the Sun (as given by Kepler's Third Law). For the Earth, of course, the period is one year. Inferior planets have periods shorter than that, superior ones have longer periods.
The synodic period of a planet is a measure of how long it takes to appear in the same place as seen from Earth (typically with respect to the Sun). For planets close to the Earth, both our orbit and theirs are significant factors in determining the period. For distant planets, the period is determined almost completely by our own sidereal period, since the distant planet only moves a little in a year.
A planet that is far enough away is moving so slowly that it only shifts a little against the background stars over one orbit of the Earth, so its synodic period is very close to Earth's sidereal period.
