"Michael McNeil" wrote in message
news:41a088dea94ba804868854040cee2243.45219@mygate .mailgate.org...
Thanks John Zinni and Mike Dworetsky (needless to say I ignored the
Wally)

This sounds like the early proposal that the Sun might be slightly
oblate,
which would be enough to produce a small perihelion advance of 43" per
century. Another theory proposed that there is a small planet interior
to
Mercury. There are several observational demonstrations that these
explanations are not correct.

No sign of of an inferior orbiting body of any significant size has ever
been detected. Observations of the Sun have shown that the figure is
very
accurately spherical. And the amount by which GR would affect the
perihelion advance of Venus and Earth is sufficiently different, from
that
due to the oblate Sun models, to rule out the latter by direct
measurement
of perihelion advance.

I presume that the time function(s) used in relativity have exact laws
or whatever and are not just numbers added to the algorythms to correct
the other functions?

If the centre of mass of the sun is not the centre of the sun (rather in
the manner of mascons on earth) this would be the oblateness you are
talking about or is there something else?


No, the oblateness proposal was describing a very small flattening of the
Sun at its poles, sort of like Jupiter only much smaller. The centre of
mass is still at the geometric centre. The main problem with this theory is
that the amount of polar flattening needed (or equatorial expansion) was
that it required a larger than observed flattening to produce the perihelion
advance of Mercury.

I appreciate that the problem of looking at the sun is that radiation
(or heat and light) make observations of anything past macula
impossible. Or have I got that wrong?


I'm not sure what you are asking, but the method used to measure the true
oblateness of the Sun required making corrections for the relative
brightness
of faculae, maculae, etc. in the measurement of shape. The method basically
involved masking out the central part of the solar disk almost up to the
limb and examining the brightness of each part of the limb regions.

I had a link to someone's home page that showed a mathematical
relationship between the distances of the planets. (Not Bode's Law.
Something to do with the square or cube of the distance fom the sun of
one planet being the distance of another (or some such function of that
one) It was an attempt to relate the distances with Pythagoras' Theorem.
It worked too except it put the centre of the solar system outside of
the sun.)

Not Johannes Kepler? Bode's Law worked fine for known planets but not once
Uranus and Neptune were discovered.

In any event I doubt that this has anything to do with Mercury, as the
effects of planetary perturbations were already taken into account in coming
up with the figure of 43 arcsec per century.

Unfortunately that link went too. Not that the concept was useful in any
known way (as far as I know that is. -Rather like Desargues' Theorem.)

--
Mike Dworetsky