Re: All answers to C S Lewis


<carlip-nospam@xxxxxxxxxxxxxxxxxxx> wrote in message
news:dq9105$ku9$1@xxxxxxxxxxxxxxxxxxxxxx
> al <almond@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
> [...]
>
> > Mercury's orbit explained without relativity
> > A most satisfying element of support for Einstein's General Theory of
> > Relativity (GR) has been its accounting for the residual precession of
> > Mercury's orbit. In recent years, however, a rival explanation has been
> > found in the non-symmetric gravitational field of the sun. Surface
> > oscillations of the sun betray hidden internal rotation, which produces
> > asymmetry in the sun's gravitational field. By applying the distorted
field
> > in predicting the orbit of Mercury and the minor planet Icarus,
astronomers
> > are more successful than when they use the GR. The authors of this paper
> > claim that GR averages some 2 standard deviations off the mark, while
> > results -using the nonsymmetrical gravitational field of the sun are
right
> > on the money!
>
> > (Campbell, L., et al; "The Sun's Quadrupole Moment and Perihelion
Precession
> > of Mercury," Nature, 305:508, 1983.)
>
> You may have noticed that this paper is 23 years old. Since then,
> observations of "surface oscillations of the sun" and the resulting
> "internal rotations" have improved drastically, in part because of
> satellites dedicated to observing the Sun. See, for example,
>
> Kuhn et al., "The Sun's Shape and Brightness," Nature 392 (1998) 155
> Pijpers, "Helioseismic determination of the solar gravitational
> quadrupole moment," MNRAS 297 (1998) L76
>
> In addition, ground-based observations have greatly improved. See, for
> example
>
> Lydon and Sofia, "A Measurement of the Shape of the Solar Disk,"
> Phys. Rev. Lett. 76 (1996) 177
>
> And fits to planetary orbits have *also* vastly improved, in part because
> of the accumulation of much more data. See, for example,
>
> Pitjeva, Astronomy Letters 31 (2005) 340
>
> The upshot is that the asymmetry of the Sun's field is much smaller than
> the number used by the paper you cited, and there is no conflict with
> general relativity.
>
> (It's also worth noting that the particular alternative used in the
> Nature paper you cited is internally inconsistent: see Damour et al.,
> Phys. Rev. D47 (1993) 1541.)
>
> [...]
> > The Perihelion Advance of Mercury is perhaps the most discussed of all
in
> > the solar system, in part due to its high eccentricity and visibility.
> > Whilst the other inner planets, Mars, Earth, and Venus, are more
> > predictable, Mercury has defied a satisfactory equational description
for
> > several centuries. A wide spread fallacy is that only Einstein's Theory
Of
> > General Relativity can accurately predict the PA of Mercury. In fact,
German
> > school teacher, Paul Gerber, first devised the equation Einstein used in
> > 1898 - 18 years before General Relativity was published.
>
> What Gerber did was to simply assume an arbitrary extra velocity
dependence
> of the Newtonian gravitational potential -- that is, not just that the
> potential depended on the source's position, but that it depended in a
> rather peculiar manner on the velocity of the source. There seems to have
> been no particular physical justification for this dependence -- von Laue
> concluded that Gerber probably worked backward from the answer, and Pauli
> characterized it as "completely unsuccessful from the theoretical point of
> view." In any case, it was not surprising that *someone* came up with a
> formula that worked. With the discovery that the electromagnetic
potential
> had a velocity dependence, it was natural to guess that the same might be
> true for gravity, and a dozen or so different functional forms were tried
> by various physicists (none with any particular physical justification).
> Gerber was lucky enough to come up with the combination that, in
retrospect,
> we can recognize as the weak field approximation of general relativity.
>
> It is also worth mentioning that Gerber's expression for the gravitational
> potential predicts a substantially wrong (and observationally very clearly
> excluded) deflection of light in a gravitational field.
>
> [...]
> > To say that this (the bending of light from stars by the sun) is an
optical
> > effect as if you are giving me information is just a play on semantics.
> > Anything to do with light is an optical effect. What I was saying - as
you
> > well know _ was that this particular optical effect was not due to any
> > relativistic effects.
>
> The deflection of light by the Sun (and now Jupiter) has been measured,
> using VLBI, to a precision of better than a tenth of a percent. Are you
> really claiming that just by coincidence, some nonrelativistic effects
> consistently reproduce the predictions of general relativity to this
> precision?
>
> Try looking at
>
> Robertson et al., Nature 349 (1991) 768 (74 radio sources,
> over 300,000 VLBI observations; fitting not just deflection
> at the limb of the Sun, but the amount and functional form
> of deflection as a function of distance from the limb; standard
> error of .2%)
>
> Lebach et al., Phys. Rev. Lett. 75 (1995) 1439 (VLBI
> measurements of two extragalactic radio sources at three
> frequencies; a total of over 20,000 measurements; standard
> error of less than .2%)
>
> Shapiro et al., Phys. Rev. Lett. 92 (2004) 121101 (results from
> 2500 24-hour VLBI sessions over 20 years, with 87 VLBI sites
> and 541 radio sources; standard error of .04%)
>
> Note in particular that the Robertson et al. paper was a whole sky survey.
> Of the 342,000 observations used, only 800 were within six degrees of the
> Sun. The same is true of Shapiro et al. In fact, Shapiro et al. checked
> explicitly that if one excluded sources on a line of sight close to the
> Sun, the results didn't change. This rules out any "Solar atmosphere"
> or refraction explanation rather conclusively.
>
> Steve Carlip
Do any of your above references refer specifically to the perihelion of
Mercury? You have failed to make this clear.
al
>


.

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