🚀 go-pugleaf

In article <BzFDCt.KFH@ccu.umanitoba.ca> mayor@ee.umanitoba.ca writes:

>
>During the new moon, the moon is on the same side of the earth as the sun.  During
>full moon, the moon is on the OPPOSITE side of the earth as the sun.  So shouldn't
>the gravitational tugs oppose each other during full moon and reinforce each other
>during the new moon only?
>

Nope.  You're forgetting that tides form on both sides of the Earth at the same
time.  Recall that the Moon not only pulls on the water directly "beneath" it, 
it also pulls the Earth away fro the water on the other side.  This latter
effect produces another high tide, directly opposite the "obvious" one.
This is why high tides occur roughly 12 hours apart, rather than the 
slightly-over-24 you'd expect if high tide only occurred when the Moon was at 
its highest.

Some ASCII diagrams may help:


        (E) ----  M 

Imagine that the parentheses represent a layer of water or whatever
around the Earth. With the Moon here, the portion of the Earth closest to the 
Moon (the ")") gets pulled towards the Moon; simultaneously, most of the rest 
of the Earth ("E") gets pulled away from the far side (the "(").  You end up 
with

        ( E ) ----- M

You get two tidal bulges.

Its should be clear that the Sun will augment these whenever it, the Moon,
and the Earth are almost in a straight line -- namely, at either
full Moon ( S - E - M) or new moon ( S - M - E).

Hope this helps.

>I think so.  Maybe I'm wrong.  Think about it.

-- 
David Nash                  | Gradual Student, Chemistry
                            | University of Illinois (Urbana)
(dnash@uxa.cso.uiuc.edu)    | This .sig is made of 100% recycled electrons.
(nash@aries.scs.uiuc.edu)   | No binary trees were killed to make it.