Perihelion shift of S2

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In sci.astro Cesar Sirvent wrote:

[...]
However, I understand that for AS Cam and DI Her the disagreements
are not likely due to poor measurements, right?

It's not clear.

It is perfectly clear that 84 years of measurements, reviewed by dozens of
researchers all clearly show that the DI Her measurements are excellent.

I would suggest reading the second paper of Claret
that I cited (A & A 330 (1997) 533), section 3.10, which discusses
the observational issues. Claret quotes Guinan and Milone, for
example, as stating that the difference in the periastron advance
for DI Her obtained using photographic, visual, and photoelectric
measurements and only photometric data can reach 270%.

It's still a 20 sigma effect against GR.

And why would Steve quote Claret, instead of Guinan and Milone about what
Guinan and Milone stated? Unless Steve never bothered to read Guinan and
Malone (available on the web), and read only papers that claim to support
GR?

Further,
the photometric observations have covered only .1% of the apsidal
motion period.

Irrelevant.

If I had to guess, I would put even odds on problems with the
observations and a fairly prosaic physical explanation, such as
a third body, with some radical problem in GR a distant third.

see 1985 Guinan:

"Although it is possible to create mathematically a third member of DI Her
that can resolve the discrepancy between the observed and the theoretically
expected apsidal motion, there is no observational data to support its
existence...."

DI Her is a pair of B stars (B4 and B5). The postulated companion is
constrained to be between a B9 to A0 star, due to known variations in the
light curves, at extremely high inclination to the eclipsing pair (exceeding
46 degrees) -- an unstable configuration. And a high-inclination A0 star is
really hard to miss.

(For the record, I, like most of the people I know who work in the
field, would *love* to find some set of good observations that
disagreed with GR -- it would make life much more interesting.

A transparently untrue statement -- because Steve won't examine well-known
and well-documented 'anomalies' such as DI Her. Steve's knee-jerk response
is to claim the observations are bad -- when the observations of DI Her are
FAR better tests of GR than the cases he uses for 'support' of GR.

It's precisely because I recognize this bias, though, that I'm not
willing to leap at claims that aren't well-substantiated and that
have possible boring explanations. If you want to find something
new, a lot of the work goes into not chasing down blind alleys --
there are just too many of them.)

DI Her is enormously well documented. It was first identified as a GR test
in 1959 -- specifically because it was so much better than Mercury (which is
a dynamic nightmare, loaded with subjective pitfalls). There have been 20
years of intensive efforts to explain the motions of DI Her -- starting with
Guinan (who is a GR-supporter, but an honest one). Observational problems
have been ruled out. Third bodies have been ruled out -- to all but the
priesthood.

But Steve pushes complex studies of distorted stars where the GR effect
is mere noise on a signal.

--
greywolf42
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