The moon are a lot closer than the sun. Therefore the gravitational
force of the moon varies more over the earth's surface. It is the
variation in the gravitational force and not the force in itself that
creates the tides.

The moons pull on a water-molecule directly under the moon is larger
than
on a molecule on the far side of the earth, actually it is larger than
"the average pull on the whole earth", and here the moon pulls away
from the earth.
On the far side of the earth (seen from the moon) the gravitation from
the moon is less than average and at this point the moon pulls toward
the earth. In the middle (when the moon is in the horizon) the moons
pulls with the same as on the earth as a whole, and there is no
vertical component, so here the water-molecule is "unaffected" by the
moon.

On both sides the change in gravitational pull from the moon reduces
or counteracts the gravitational force of the earth on the
water-molecule(making it lighter, so to speak).
This should explain why there is to tides a day, one when the moon is
culminating and one when it is on the other side.

Peter S/Y Anicula

"Donal" skrev i en meddelelse
...

"Thom Stewart" wrote in message
...
Marty,

Right you are! Tell Donal to mark you up for One Point.

The Tides use the Moon Calender:^)
That is also the reason that Tide rides are possible.

I'm afraid that I can only award Marty 0.75 of a point.

I'm about to dissappear for a couple of days, so I'll explain when I
get
back.

[hint] The sun has a much greater gravitational effect on the Earth
than
the moon. So why does the moon seem to have a greater impact on the
tides?



Regards


Donal
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