How is the tide and moon and sun tied together?

As I'm sure you know, the Earth is gravitationally bound to both the sun and the moon, which we can consider as two separate systems (Earth-moon and Earth-sun), each involving mutual attraction between two massive bodies.

Newton's law of graviation determines the overall force, which is proportional to the product of the two masses and inversely proportional to the square of the distance between them. If the mass of the Earth were concentrated into a compact point, there wouldn't be much more to say.

In reality, however, the Earth's diameter is relatively large in relation to the distance between it and the moon. Thus the parts of the Earth closer to the moon experience a slightly greater force of attraction than the parts of the Earth farther from the moon. This differential gives rise to tidal forces that complicate the picture.

These tidal forces cause the earth to slightly elongate along a line between Earth and moon, producing a bulge extending from the near side to the far side of the earth relative to the moon. The entire substance of the Earth is affected, including its oceans, continents, and molten interior.

Meanwhile the Earth is rotating on its axis, so any given geographical location on the surface is actually rotating into and out of the tidal bulge twice a day, once on the near side and once on the far side. We mainly notice its effect on the oceans (the ocean tide comes in and out twice a day) although dry land also rises and falls to a lesser extent.

The same explanation applies to the Earth-sun system. The sun is of course much more massive but also much farther away. Overall the tidal forces arising from the sun are about half the magnitude of those of the moon.

The sun and moon exert separate tidal effects along the lines conecting them to the Earth. So depending on whether the sun and moon are aligned (such as during a full moon or new moon) or perpendicular (half-moon), the overall tides are at a maximum or minimum, respectively.

Hope that helps.

oh wow thanks so much you helped very much. Made it much easier for me to understand!

Professor, that was a very good answer, I learned quite a bit.

Thank you both for the compliments. It's a pity this Science board doesn't see more activity, but then I myself don't visit very often anymore...

Hi, Prof...

If you think this science board doesn't show much activity, the 'other place' (Washad's Answerpoint) shows practically none at all.
Of course we both remember the Jeeves days when questions came in by the bunches per day, many from one-time visitors looking for an answer. This site has become more of a discussion/trivia/debate/game room site amongst members rather than a Q&A forum. As one old timer once said, 'too many chiefs and not enough indians'. But all in all, the makers of this site (KK, Karrow, moderators, enthusiasts, et al) have done a great job here, every question gets answered, Answerpool is here to stay. Keep in touch.

Gerry, I monitor the "other place" from time to time, and it seems to be overrun with religious nuts. Not my cup o' tea.

But this site (AnswerPool) most definitely has some talented people running the show.