Re: All answers to C S Lewis

"al" <almond@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
news:dq99tk$dvi$1@xxxxxxxxxxxxxxxxxxxxxx
>
> <carlip-nospam@xxxxxxxxxxxxxxxxxxx> wrote in message
> news:dq9105$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

Pitjeva, Astronomy Letters 31 (2005) 340 specifically deals with the use of
radar measurements to give very accurate values for the perihelion of
Mercury. It also shows that this precession is in agreement with both GR
and the measurements of solar oblateness determined by other experiments
using independent methods.

Unlike yourself, Steve has gone to the trouble to give a detailed list of
the most recent papers on the subject of the General Relativistic advance of
the perihelion of Mercury, the oblateness of the Sun, and the displacement
of star positions due to GR bending of light in the Sun's gravity field.

In contrast, we are still waiting for you to give any references to the
"hanging star" business you ranted on about.

--
Mike Dworetsky

(Remove "pants" spamblock to send e-mail)

.

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