Originally posted by abcddcba
Originally posted by intergalactic fire
reply to post by Aestheteka
can anyone tell me why they say the moon rotates at the same speed as the earth which is why we always see the same side of the moon? i've been
wracking my brains for years trying to figure out how that works. you would think if that were the case one side of the earth would always see one
side of the moon and the other side of the earth would see the other side of the moon always.
That's called Tidally Locked
, and many if not most moon's orbits and rotations are tidally
locked to their father planet. If the moon had no rotation we would see both sides as it's phases change, about every 28 days.
You may then wonder, why are most moons tidally locked and not planets?
good question but we do observe a different kind of tidal lock in planets close to their stars, especially exoplanet gas giants very close to their
star, closer than mercury. Imagine a Jupiter size planet closer to the sun than Mercury, I don't mean just closer, twice as close and more.
Speaking of Mercury it has a sort of tidal lock with the sun (some call it a tidal lock), but it is called orbital/rotational resonance meaning three
days equalling two years. Kind of strange to imagine a work week lasting almost four years.
Our solar system is full of very different kinds of orbits and rotations of the planets and their moons. Venus rotates retrograde/backwards, and it is
very close to getting a tidal lock with the sun as it's year is longer than it's day. Some say Venus is rotating the same way as the other planets
it's just upside down, north pole facing south almost 90º, that is another debate.
We have Uranus tilted on its side, actually over 90º in respect to its orbit, so it moves kind of like a bowling ball around the sun. The butt of
Uranus, no sorry (so many jokes can be made of the poor planet), the south pole of Uranus never faces the sun, which creates the strongest winds of
any body in our solar system, (sorry, had to insert that one too).
Neptune's large moon Triton, (would be considered a planet on its own if)...it wasn't in a tidal lock with Neptune but the wonder doesn't stop there,
Triton orbits Neptune with the same side facing the planet, retrograde, in the opposite direction that Neptune spins, the only 'large' moon that does
Many other wonders of the moons, two Saturnian moons trade orbits. Then there are Trojan moons, but I'm getting a bit off topic now. Orbital dynamics
of the bodies in our solar system alone could fill a whole forum of threads. Hope you have enough interest to look into some of the wonders of
orbiting bodies around our sun and the sun's planets.
One last thing also, our solar system's orbital plane is also tilted in respect to its rotation around the galaxy, by a whopping tilt of about 60º,
and our system bobs above and below the galactic plane during a rotation/orbit.
I'm not sure if that illustration is correct, I believe north of earth's ecliptic faces the galactic center, so we sort of pinwheel around the galaxy.
I wasn't going to spend much time on that and just grabbed an illustration from the ATS archives.
edit on 5-11-2011 by Illustronic because: (no reason given)