Re: Bulges

[Jim Green <JMGreen@sisna.com>]

> I doubt that. I think the component frequencies associated with the
> planets' tidal forces are indistinguishable from the solar term, namely
> one cycle per 24 hours. Besides that, I think that they are too small to
> be important, or even detectable.

Well, no one "detects" the various harmonic forces directly.  However, note
that, depending on the model, there may be over 100 harmonic terms in the
calculation and according to the data before me the amplitude of the weakest
harmonic considered is 5 or more orders lower than the principal lunar
harmonic, M2.  A couple of years ago when this topic was rampaging on the
list, I made a calculation of the principal Venus force, V2 say, and
compared with the lowest order lunar and solar harmonics.  I found them to
be comparable.  Of zzzzzzzzzzzz I am senile and may have made an error.   I
will check.


> Tide tables are not generated by doing fourier transforms on tidal data.
> They are generated by doing harmonic analysis, quite a different process.

Well they *used to be* harmonic reductions, but I understand they now do a
Fourier transformation -- the result should be the same -- the Fourier
transform should yield the same frequencies as the astronomical force
calculations.  The coefficients would need to be empirical in any case.  I
will consult with my friend at NOAA and check.

HOWEVER, I am starting to worry about my position on other grounds.

I think it clear that the Newtonian tidal bulges are a myth.  But Newton
assumed a rigid Earth.  I need to look more closely at the crustal motion,
which likely *does* obey the equilibrium theory and *does* have "tidal
bulges".  I thank the crustal motion is of the order of a few feet (20ft
???) -- If this *is* the case and if this is what David Bowman holds, then
the story changes.  You see David is worried about the theory of some
planetary geophysicists that it is a "tidal bulge" which applies torque to
the Moon and slows it's orbit.  If David, et al are willing to say that it
is the crustal bulge which does this then I relent.  If however there are
those who think there are Newtonian water tidal bulges which cause this
torque, then I must continue to say myth.  (And I don't see the geo people
saying this.)


Jim Green
JMGreen@sisna.com