Originally posted by Phage
reply to post by CLPrime

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When you have a small mass (like the Moon) orbiting a large mass (like the Earth) at a sufficiently close distance, the gravitational pull of the large mass causes the small mass to bulge in the direction of the large mass.

The bulge actually occurs on two sides of the object; the side near and the side opposite the other body. That's why there are two high tides each day. The reason being the gravity gradient across the diameter of the body. Same result. I just thought I would confuse things by throwing that in there but that double bulge does cause a greater torque than a single one would have.

It should also be noted that it is both bodies which experience the effect. The Earth is still in the process of becoming tidally locked with the Moon.

Originally posted by PurpleChiten

Originally posted by Phage
reply to post by CLPrime

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When you have a small mass (like the Moon) orbiting a large mass (like the Earth) at a sufficiently close distance, the gravitational pull of the large mass causes the small mass to bulge in the direction of the large mass.

The bulge actually occurs on two sides of the object; the side near and the side opposite the other body. That's why there are two high tides each day. The reason being the gravity gradient across the diameter of the body. Same result. I just thought I would confuse things by throwing that in there but that double bulge does cause a greater torque than a single one would have.

It should also be noted that it is both bodies which experience the effect. The Earth is still in the process of becoming tidally locked with the Moon.

Yup! And if the moon had water on it, it would experience high and low tides due to the earth just like the earth does due to the moon

Tides come about because the ocean's waters are mobile (plastic) & are able to respond to the changing tidal generating forces exerted between the earth, Moon & SUN in their orbits.

These forces vary with time because of the changing relative positions of the earth and Moon during the 29-day lunar cycle and the annual cycle of the relative positions of the earth and Sun.

The PRIMARY tidal influence is the Moon - the forces between her & the earth produce an Elliptical envelope with its long axis pointing towards the Moon. Since the earth is spinning (once/24hrs), the high waters so produced and their intervening lows are progressively moving around the earth to produce a Semi-Diurnal (half daily) tidal pattern involving 2 highs and 2 lows each day.

Since the Moon is orbiting the earth each lunar month, it will have moved eastwards about 13 degrees of it's orbit each day. This causes the semi-diurnal tide pattern to repeat itself every 24hrs and 52mins (a lunar day). The net effect is that the tide times move back about an hour a day here on this rock. The latitude on the Earth that the moon is overhead varies about 25 degrees either side of the equator during the lunar month. Because of this resultant shift in the plane of the moon's influence, there is generally an inequality in the 2 highs and 2 lows each day.

Only when the moon is overhead the equator will the highs be equal (and lows be equal) - this happens about once every fortnight. The SUN also exerts similar influences on the tide pattern in similar ways, but to a lesser extent than the moon and over 365-day cycle rather than every lunar month. In theory, the tide that is experienced is a result of the interaction of the Moon's and the Sun's elliptical envelopes.

OTHER TIDAL INFLUENCES:
1. The continents disrupt the free movement and at depths, shapes and current flows in each tidal basin (Pacific ocean for instance) modify the response. These changes can be extreme such that the expected semi-diurnal patterns become only one high and one low each day (diurnal) - Karumba in the Gulf of Carpentaria and Koolan/Cockatoo Islands are prime examples. Again the rises and falls don't occur simultaneously over the surface of the ocean basin but seem to radiate outwards and/or rotate around each basin.

2.Strong and prolonged winds - the effect of wind on tidal heights & times is variable and is, in turn, modified by the coastal topography. In general, it can be said that a strong "onshore" breeze will "pile-up" the water and cause higher tides than predicted; "offshore" breezes will have the opposite effect.

3. Unusually high or low barometric pressures. Low pressure systems tend to raise sea levels - sometimes by more than 2 meters in intense cyclones and high-pressure systems tend to lower them.