I understand the reason for asking this question on Astronomy. The OP likely assumed that the answer to his question had something to do with gravitational influence of astronomical bodies.
That said, the question is about tides on Earth and the answer is Earth science based. Robert Cartaino has correctly pointed out that this should lead to it being off topic.
Because this question is of reasonably good quality and already has a couple of good answers, my inclination is to leave it alone for now then migrate it to Earth Science once it hits beta (an assumption, I know, but I think it is a pretty good one).
What does the community think?