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Re: Earth's rotational speed



After some more looking and reading, a number of other errors popped out:

1. 2.1.1 The righting force which produces axial precession is actually
applied at the equator and not at the poles and is a result of the inverse
square variation in force. This is easily seen for a uniform spinning disk
with an axis tilt. When it is tilted toward or away from the sun, there
will be a torque trying to right it, while in "spring or fall" positions
there should be no righting force. One wonders if this seasonal variation
in the torque has any consequences.

2. The diagram by moment of inertia is actually for torque.

3. "The Moon's effect is about 54% of the total - gravitational force is
proportional to the masses of the interacting bodies, but inversely
proportional to the square of the distance separating the bodies so although
the Sun outweighs the Moon by a factor of 10 million the fact that it is
almost 400 times further away than the Moon gives the Moon the gravitational
edge" is actually wrong 1/400^2 does not outweigh a factor of 10 million.
Again the mistake is the fact that the tidal force goes as the gradient and
not the force.

4. ? The rip tide I thought was an effect that happens when a channel opens
in a sand bar so that most of the outgoing water tends to flow through the
breach. This produces a very strong current which sweeps swimmers out to
sea. http://www.newton.dep.anl.gov/askasci/gen99/gen99139.htm This may be
debatable as another source says it should properly be called a rip current
and the rip tide is a misnomer. I could not find it in either my
encyclopedia or dictionary.

I suspect there may be some other semantic or physics boners. One hopes
that this was written by someone other than the professor.

John M. Clement
Houston, TX


Check out
http://www.ldeo.columbia.edu/users/jcm/Topic2/Topic2.html which
is the source for the following:

2.5 Length of Day Variations.

While it might seem fairly incredible the length of the day is
changing all
the time -- not by an amount that anyone would notice, but by
amoints that
are easy to detect instrumentally. The changes are only a few
milliseconds
(a millisecond is one thousandth of a second) but they are very easy to
measure. The record below shows that there are very regular
variations and
also very irregular variations. All of the changes must in some way be
caused by the re-distribution of mass over the surface and with in the
Earth. Seasonal changes (curve d) are caused by the change in ice
volume and
relative amounts of water in the atmosphere from summer to
winter. Longer
period changes and shorter period changes (curves c and e
respectively) are
more difficult to explain. Some are caused by the phase of the
El Nino --
the Earth rotates differently in an El Nino year than in a La Nina year
because these phenomena change the distribution of wet and dry
parts of the
world. Even longer period changes must be caused by processes
in the deep
Earth that move masses around such as subduction of large slabs of
lithosphere. The cause of many of the longer period signals is not well
understood.



----- Original Message -----
From: "E.C. Muehleisen" <docmule@HOTMAIL.COM>
To: <PHYS-L@lists.nau.edu>
Sent: Monday, December 31, 2001 3:15 PM
Subject: Earth's rotational speed


I have been aware that the earth's speed about the sun varies
as we travel
on our elliptical path. However, I have read that the earth's
rotational
speed varies though the year. Would someone be so kind as to
explain this
change in omega and also explain the implications on L and the
conservation
of angular momentum.
Perhaps this will prompt a return to things of physics rather than
government.
Then a last barb on the much ballyhooed tax "rebate." A
quote:"Sometimes I
wonder if the world is being run by smart people putting us on or by
imbeciles who really mean it."

Too much of a good thing is wonderful!




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