Post by LouPost by Lou[[Mod. note -- I have inserted a few blank lines so as to more clearly
mark the transitions between quoted material and what this author has
written. -- jt]]
Post by Zachary Alexander P.An article about Black Holes, Neutron Stars, Fusion, Electromagnetism and Gravity.
https://docs.google.com/document/d/1-o08Dao8HJhwgJH-09vzHwvinhwbfKTOY6_gWmpXWPg/edit?usp=sharing
The article is 38 pages long in print format of font size 11.
38 pages may seem daunting, but lot of the space is taken up by
relevant images that express the ideas.
This article is highly speculative, but for good reason since it is of
things that show anomalies in the
standard model. Take your time while reading it to give it some
thought before you comment.
I haven't read the whole thing, only up to page 8. But I found a
He's blaming light bending around the sun on refraction of the corona.
He has NO calculation of how big that would be: scientists have, and
it's not nearly big enough.
This is a false assumption. The author of the paper probably didn't do
a calculation of what the refractive index...because the density of the
Corona and thus its refractive index isn't known! Quite how "scientists"
did the calculations of its refractive index is the big question Gary should
be asking.
Besides that, Cassini measured the angle at
two different frequencies because refraction due to the corona is
frequency-dependent. Their results disagreed with refraction on two
counts.
Once again a problem with "scientists" deciding what the refractive
index of the Corona is. (Even though They havent the faintest idea
of what the density and thus refractive index of the Corona is.)
And regarding "seperate frequency" measurements by Cassini.
Interesting non point considering any viable comparison should be
between two very different frequencies in simultaneous observations.
Like radio and x ray. Which have never been made. Cassini did it
in two almost identical radio frequencies.
Based on this, I don't believe he thinks deeply enough. Besides, I have
my own biases :-)
Gary
[Moderator's note: Indeed. I glanced over it and there are several
questionable things in it. On the whole, I would say that it is too
speculative. -P.H.]
Speculative maybe,...but I see no evidence to rule it out in Gary's post.
[[Mod. note -- The author is mistaken as to the Cassini measurements
and their interpretation as gravitational time delays (the Shapiro effect)
versus plasma delays.
I wasn't disputing the assumptions about GR made in the paper.
I was only pointing out the paper, Gary or any other source have no
confirmed measurements of the density or refractive index of the corona.
How then is it possible to rule out refraction..if we don't know
what the refraction index of the corona is?
Post by LouLooking at
B Bertotti, L. Less, and P. Tortora
"A test of general relativity using radio links with the Cassini spacecraft"
Nature 425, 374-376
open-access copy currently available at
https://lorentz.leidenuniv.nl/research/vanbaal/DECEASED/ART/gr-test.pdf
we see that Cassini actually used frequencies of 7.2 Ghz and 34.3 GHz
(uplink) and 8.4 GHz and 32.0 GHz (downlink), which are clearly not
"almost identical".
Almost identical is is 42 to 8 ( Cassini test radio range in millions of nano meters.)
A good spread to test Refraction would be a spread of
42 to 0.0000001 ( radio to x ray)
Post by LouMoreover, figure 2 of that paper shows that the calculated gravitational
signal has a time variation closely matching the theoretical prediction
(equation (2) of the paper), which would not be the case if the frequency
shifts were actually caused by plasma delays.
? I see nowhere in the paper you cite or elsewhere in the published
domain that provides conclusive and reliable in situ measurements of
the corona, its density and refractive index. Any assumptions made
are without substantiation.
In fact the current best method to measure a refractive index is
to measure how much light is bent by the medium in question.
Is that not correct?
Post by LouThe interpretation as
gravitational time delay is further strengthened by the consistency
checks the authors describe in the "Method" section on p.376 of that
paper, and by the results shown in the supplementary figure (currently
available open-access on the /nature.com/ website.
Of course...but the question is not if GR can supply the correct prediction.
The question is what is the measured density and refractive
index of the corona. The answer is...no one knows.
Post by LouThe Cassini results are also consistent with a wide range of other
measurements of general-relativistic light-bending and time delay.
See, for example, figure 2 of Clifford M Will's fascinating paper
arXiv:1409.7812.
-- jt]]
If I can also point out a quote from the above cited paper (author
Bertotti et al.) They claim only GR can correctly predict the anomalous
preccession of Mercury. This is a false claim. In fact Le Verrier did
correctly model the observed preccession of mercury by spreading
the suns mass across its volume. Although he incorrectly assume
the presence of the planet Vulcan, his N3 body calculations did
spread the mass of the sun across its volume. Proving beyond
doubt that the mass of any object like a planet is spread across
its volume. Not confined, as Newton thought, to a singularity at its
center. This conclusion is confirmed by experiments such as
Schiehallion
(It's no wonder Newton was opposed to these types of
experiments. They contradicted his own assertion that all of the
planets mass was located at its theoretical center)
[[Mod. note --
1. Since the solar corona's index of refraction is frequency-dependent,
measuring the Shapiro delay at multiple frequencies does in fact
allow the corona's (frequency-dependent) index of refraction to be
calculated -- that's why Cassini used multiple frequencies!
It's not specified anywhere in the literature I read that Cassini did *not*
find any frequency dependent deflection. Nor is it clear if
the data from each frequency was collected simultaneously. An
important proviso.
I read the slac.standard.edu paper on the actual test data and page 2
confirms coronal dispersion was highly variable over short periods.
And then says...that because of this variability both 32 and 8 million
MHZ data were combined as one for deflection analysis.
If this is true then so much for seperate frequencies.
And finally could refraction between 42 and
8 million MHz be even quantifiable using Cassini?
I would have thought that time delay due to refraction
Between the two low frequency radio frequencies would be
impossibly small to measure anyways.
[[Mod. note -- The Cassini experiment did indeed measure the time delay
in question. Quoting from the caption for supplemental figure 1 of the
Bertotti et al paper cited above:
| The complete fractional frequency shift is the sum of three parts:
| the non-dispersive part $y_{nd}(t)$ (which includes the gravitational
| signal) and the time dependent plasma contributions $y_\wedge(t)$ and
| $y_\vee(t)$, proportional to the columnar electron content along the
| beam in the up- and the downlink, respectively. With three independent
| observables, the three quantities $y_\wedge(t)$, $y_\vee(t)$ and
| $y_{nd}(t)$ are separately determined.
Note particularly that last clause: "the three quantities $y_\wedge(t)$,
$y_\vee(t)$ and $y_{nd}(t)$ are separately determined".
-- jt]]
Post by Lou2. Another way to avoid contamination by solar-corona effects is to measure
the bending of *visible* light. This is hard to do with ground-based
experiments, but the ESA's Hipparcos satellite measured light bending
over *the entire sky*, including regions of the sky > 90 degrees away
from the Sun (where the effects of the solar corona are negligible).
Why would refraction not give the same inverse square relationship to
distance that gravity has? The density gradient of the plasma from the
corona to the farthest part of the solar wind "bubble" has to also follow
the same inverse square relationship.
[[Mod. note --
1. Because there's an integration over the entire path length,
gravitational light bending (or time delay) doesn't vary as the
inverse square of the impact parameter (the closest distance between
the path and the center of the Sun). As you can see from equation (1)
of the Bertotti et al paper, the actual variation is *logarithmic* in
the impact parameter. (There's a more detailed calculation in, for
example, sections 7.1 and 7.2 of Clifford M Will, "Theory and Experiment
in Gravitational Physics", 2nd edition, Cambridge U.P.)
2. Unfortunately my wording in a previous moderator's note was sloppy:
I wrote that "the ESA's Hipparcos satellite measured light bending
over *the entire sky*, including regions of the sky > 90 degrees away
from the Sun (where the effects of the solar corona are negligible)."
That final statement is true, but I gave the wrong reason for it:
the effects of the solar corona *on visible light* are very small
*everywhere* in the sky, including even lines-of-sight which pass
quite close to the Sun. The importance of Hipparcos's being able
to measure light bending > 90 degrees away from the Sun is for a
completey different region: to maintain a stable thermal environment,
Hipparcos was designed to *never* point its instantaneous lines-of-sight
close to the Sun.
-- jt]]
Not to mention Parker probe. Notice, contrary to assumptions,
it provided many new unexpected properties of the Corona.
Post by Lou3. We actually know the Sun's density profile (and hence its quadrupole
moment J_2, which is what you're referring to) very well, thanks to
helioseismology measurements .
We don't "know". We assume. Don't forget the basic rule of physics.
Assumption is not an observation.
[[Mod. note -- Arxiv:1103.1707 outlines some of the observations and
analysis (as of 10 years ago). It's pretty impressive. -- jt]]
Post by LouYou can't (correctly) model the observed
precession of Mercury (not to mention those of Venus, Earth, and Mars,
all of whose orbital precessions are also well-observed) using Newtonian
gravity and the Solar mass distribution.
Yes you can. Le Verrier did in his 1859 paper. Correctly. Or as close
as correct could be in 1859 due to uncertain measurements available
at the time.
He even is on the record for saying it wasn't neccesarily Vulcan. He
only speculated the additional source had to be outside the suns
theoretical center. And for the standards of the time...his calculations
presumably 3 body, were correct. 60 years before Einstein.
Post by Lou4. Newton never asserted that all of a planet's (or the Sun's) mass was
located at its center. Rather, he (correctly) calculated that the
external gravitational field of an extended spherically symmetric mass
"Correctly calculated"?
No he didn't. This is a false claim. If he did....why do his calculations
not correctly model the preccession of planets like Mercury?
[[Mod. note -- Newton's calculation of the gravitational field of a
spherical body (the "shell theorem") is briefly outlined in
https://en.wikipedia.org/wiki/Shell_theorem
So far as we know, Newton never calculated or modelled planetary
precessions (I don't think there's any mention of the topic in his
surviving writings). Much later, Leverrier, Lagrange, and others used
Newton's shell theorem (among many other mathematical techniques) to
calculate planetary precession -- including that of Mercury -- within
the framework of Newtonian gravitatation and mechanics.
-- jt]]
Post by Loudistribution is the same as it would be if all the mass were located
at the center. (Calculating the external gravitational field of an
extended mass distribution requires calculus, which Newton invented
in part to address this question.)
5. Newton was well aware of the possibility of experiments such as the
Schiehallion experiment (the measurement of the external gravitational
field of a mountain), but mistakenly thought that the effects would
be to small to be accurately measured. Fortunately, he was wrong.
Newton's *excuse* was that it would be too small to measure. What
he didn't want to admit was that if it was measureable...then his
assumption that one can assume that all the mass could be put
at the center was incorrect. As Mercury's preccession proved.
