Sun-Earth-Moon Gravity

My astronomy teacher has asked me to calculate gravitation pull between Earth and Sun, Earth and Moon, and Sun and Moon. Well, it turned out that gravitational attraction between Sun and Moon ( 4.369 * 10^20 N) is more than twice that of between Earth and Moon (1.986 * 10^20 N). His (and my) question is why doesn't Sun pull Moon toward itself and away from its current orbit around the Earth.I was thinking that is has something to do with angular momentum or something like that. Should I read more about planet and star creation, to find the answer?I haven't seen many threads regarding our solor system in the Cosmolgy thread, but if you don't mind can you help me out? Thanks.

Well the class that Im taking turned out to be ridiculously easy, so the professor is trying to make it more interesting for me by giving me extra assignments such as that one, so its really not my homework or anything I'd be gettting a credit for. Its just something to give me more knowledge.

I thank all of you for your feedback. Your replies have certainly clarified alot of things for me. There is still an inconsistency in my understanding, though.As far as I know gravitational pull depends on combined mass and distence between objects. Since Earth and Moon have essentially the same orbit around the Sun, it means that they are the same distance away from the Sun at any given point in time (disregarding Earth-Moon motion relative to each other). It would make sense for Earth-Sun atraction to be greater then Moon-Sun atraction, since mass of the Earth is considerably greater. I could even buy if the two forces where nearly the same, but why would Moon-Earth gravitation field be so much greater?Thanks again. Edited by Ragged, : No reason given.

Distence is the same. The only difference I see is in mass, of which Earth has alot more.Gasby, I made two separate calculations. One separate for Earth-Sun the other is for Moon-Sun. Moon-Sun gravitational force turned out to be much greater. Were my calculation wrong? Or is it even wrong to separate the two?From those calculations it turns out that Sun "requires" much greater force to keep Moon in orbit, then it does the Earth. Thats the part that I dont get.

Ok, thanks guys. I need to find my graphing calculator. Kinda hard to work with an online scientific calculator. Messed up by a factor of 2 on the Sun-Moon gravitation.