All the moons in the solar system (except for 1 or 2) are tidal locked to the planet they orbit so that one hemishere is always facing the planet. Why isn't the same true for the planets relative to the Sun?
2006-12-02 10:09:01 · 3 answers · asked by Zefram 2 in Science & Mathematics ➔ Astronomy & Space
Mercury has a 3:2 spin-orbit resonance with the sun, but it's not tidally locked - its orbital period is 88 days, it rotation period is 57 days.
Tidal locking involves the orbiting body being deformed by the body its orbiting, and then the nearer parts of the orbiting body receiving a more powerful "pull" than the further parts. The planets are too far away from the sun for the difference to have enough effect.
2006-12-02 11:30:39 · answer #1 · answered by Iridflare 7 · 0⤊ 0⤋
Mercury is tidally locked to the Sun. The answer to your question is that tidal locking is the same phenomenon that causes you to stay upright if you fall from a plane with a weight tied to your ankle. If a planet or moon is even a little bit heavier on one side than the other, as you can guarantee it will be, then the heavier side is pulled towards the object it orbits.
2006-12-02 10:41:13 · answer #2 · answered by zee_prime 6 · 0⤊ 0⤋
It has to do with mass ratio and distance. Two bodies have to be close enough to lock, Mercury is the only planet close enough to the sun for this.
2006-12-02 11:15:24 · answer #3 · answered by ZeedoT 3 · 0⤊ 0⤋