Is it as simple as difference in gravitational pull of the moon on one side of the earth verses the other side?
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Joke answer: because that is God getting in to and out of the bathtub. And he takes a bath twice a day.
Real answer:
The tides are due to the moon's non-uniform gravitational field applying a squish and squash upon the Earth. The most flexible part of Earth is the oceans, hence they result in the most tidal distortion.
The extreme tidal influence (that makes the oceans rise) occurs when the moon is directly overhead...OR...directly opposite overhead. BOTH of these cause the most extreme tidal distortion, as counterintuitive as it may seem. The mathematics are complicated, but essentially you need to think of the CENTER of earth experiencing the bulk of the force of the moon, and think of the FORCE DIFFERENCE from that being applied to both sides of the Earth.
A horizon moon causes the tidal distortion that flattens the oceans...and makes a low tide.
High tide triggers due to zenith moon AND antizenith moon occur twice a day, because the Earth makes a rotation each day.
Low tide triggers due to a horizon moon occur for both rise and set of the moon.
The net effect is that you get two high tides and two low tides each day.
DO NOT EXPECT the tide triggering position of the moon to correspond exactly to the resulting tide time. WHY? Because the oceans have an INERTIAL LAG. They are a massive body...they need time to respond to the force to cause the result.
Because the moon orbits Earth (rather than being locked to a perpetual moon phase)...the tide times will PROGRESS by about 50 minutes each day. The period of high tide-low tide-high tide lasts rather than exactly 12 hours...it is more like 12 hours, 25 minutes.
TO A LESSER EXTENT, the sun also causes tides. About half the influence as that due to the moon.
When the sun and moon and Earth (in any order), form a straight line (as during full moon and new moon)...the effects add in superposition, and create the most extreme tides. We call these...spring tides.
When the moon sight from Earth is perpendicular to the sun sight from Earth (as during either type of half moon), the sun's tidal distortion nulls some of that due to the moon. We hence get the least extreme tides. We call this...neap tides.
Real answer:
The tides are due to the moon's non-uniform gravitational field applying a squish and squash upon the Earth. The most flexible part of Earth is the oceans, hence they result in the most tidal distortion.
The extreme tidal influence (that makes the oceans rise) occurs when the moon is directly overhead...OR...directly opposite overhead. BOTH of these cause the most extreme tidal distortion, as counterintuitive as it may seem. The mathematics are complicated, but essentially you need to think of the CENTER of earth experiencing the bulk of the force of the moon, and think of the FORCE DIFFERENCE from that being applied to both sides of the Earth.
A horizon moon causes the tidal distortion that flattens the oceans...and makes a low tide.
High tide triggers due to zenith moon AND antizenith moon occur twice a day, because the Earth makes a rotation each day.
Low tide triggers due to a horizon moon occur for both rise and set of the moon.
The net effect is that you get two high tides and two low tides each day.
DO NOT EXPECT the tide triggering position of the moon to correspond exactly to the resulting tide time. WHY? Because the oceans have an INERTIAL LAG. They are a massive body...they need time to respond to the force to cause the result.
Because the moon orbits Earth (rather than being locked to a perpetual moon phase)...the tide times will PROGRESS by about 50 minutes each day. The period of high tide-low tide-high tide lasts rather than exactly 12 hours...it is more like 12 hours, 25 minutes.
TO A LESSER EXTENT, the sun also causes tides. About half the influence as that due to the moon.
When the sun and moon and Earth (in any order), form a straight line (as during full moon and new moon)...the effects add in superposition, and create the most extreme tides. We call these...spring tides.
When the moon sight from Earth is perpendicular to the sun sight from Earth (as during either type of half moon), the sun's tidal distortion nulls some of that due to the moon. We hence get the least extreme tides. We call this...neap tides.
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the rotation of the moon or whatever
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Teeter-totter, see-saw.........