Gravitational Lensing : Eddington Experiment

https://ned.ipac.caltech.edu/level5/Mellier/Mellier2_1.html

2. BASIC CONCEPTS OF GRAVITATIONAL LENSING
2.1 The Thin Gravitational Lens
The standard gravitational lens theory is valid for weak stationary gravitational fields. For small angle deviations, and when the typical size of the deflector is much smaller than the propagation medium, it is possible to use the thin lens approximation (Blandford & Kochanek 1988). The lens is achromatic and acts as a plane of matter with a projected surface mass density

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This is pretty well done and dusted river, even the divine one has vanished with no more commnet after being totally demolished in every respect.
So I'll be off...you have a good day OK?

 

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pad; they are looking for " lensed " data.

Look pad you know what I would like ; is for both of us to hire the equipment we need and the people .

Then for both of us to be there at the sametime.

Right or wrong ; the whole project would be fun.

 

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Hmmm....

The lensing should give then the full physical nature of the star.

 

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Huh??? Why?? You believe that our mainstream academia friends are conspiring against the world???
You must have a hellava jib getting out of bed in the morning.
The evidence is there river and it is overwhelming.
What you believe and what cyber space you waste here spreading your Gospel and conspiracies belongs just here. It's getting you no where.

 

So are scared of this venture pad? I thought it would fun ? My mistake.

 

Gee river, isn't that a bit childish? You know, claiming someone is scared?
I trust the many experts in this field firstly and secondly have strong doubts about how genuine you really are in what you say and claim.

 

Why do you have strong doubts about how genuine I am ?

 

Achromatics ; by gravity gives no info or very little info to the star being lensed.

 

Following Professor Bertschinger's view that,

We can say that in the weak Gravitational Field, gravity is some sort of field than curvature of spacetime.

So reality of spacetime is that, it is some sort of field like electrical field, magnetic field or electromagnetic field.

"Curvature of spacetime" in "flat spacetime" seems contradictory.

 

To use the "weak field approximation" is to use Newtonian physics, or an altered version of it, to do physics rather than GR. It works as an approximation, and usually a good one because doing it in this way ignores aspects of relativity theory that play only a small role in the particular scales that the approximation is applied. Using the full power of GR would still produce a better approximation, but would often require a great deal more time and effort and not be worth it for the degree of accuracy gained.

Using such an approximation does nothing to harm the case for GR.

 

I am not talking about the math of GR. That's fine. That is working well. I am only trying to know the reality of spacetime. In the "weak field approximation", spacetime becomes flat and not curved. Though GR math is equally valid in the "weak field approximation".

 

We use the math of GR to determine how best to use a weak field approximation, but that approximation does not necessarily use the math of GR.

 

That's OK. But what is the reality of spacetime in the "weak field approximation"?

 

If we're talking about the weak field approximation, then we are likely using a flat spacetime for the purposes of calculation. That has no influence on the reality of the physical system we would be interested in.

 

I have mentioned to our divine friend that gravitational lensing can be caused by many things, individual stars, galaxies, DM, and BH's, here's another......

http://arxiv.org/pdf/1601.03051v1.pdf

Gravitational Lensing by Ring-Like Structures:

ABSTRACT
We study a class of gravitational lensing systems consisting of an inclined ring/belt, with and without an added point mass at the centre. We show that a common property of such systems is the so-called “pseudo-caustic”, across which the magnification of a point source changes discontinuously and yet remains finite. Such a magnification change can be associated with either a change in image multiplicity or a sudden change in the size of one of the images. The existence of pseudo-caustics and the complex interplay between them and the formal caustics (corresponding to points of infinite magnification) can lead to interesting consequences, such as truncated or open caustics and the violation of Burke’s theorem. The origin of the pseudocaustics is found to be the discontinuity in the solutions to the lens equation across the ring/belt boundaries, and the pseudo-caustics correspond to these boundaries in the image (lens) plane. We provide a few illustrative examples to understand the pseudo-caustic features, and in a separate paper we consider a specific astronomical application of microlensing by extrasolar asteroid belts.

 

http://arxiv.org/pdf/1502.01591v2.pdf

Planck 2015 results. XV. Gravitational lensing
Draft compiled January 12, 2016

Abstract:
We present the most significant measurement of the cosmic microwave background (CMB) lensing potential to date (at a level of 40σ), using temperature and polarization data from the Planck 2015 full-mission release. Using a polarization-only estimator, we detect lensing at a signifi- cance of 5σ. We cross-check the accuracy of our measurement using the wide frequency coverage and complementarity of the temperature and polarization measurements. Public products based on this measurement include an estimate of the lensing potential over approximately 70 % of the sky, an estimate of the lensing potential power spectrum in bandpowers for the multipole range 40≤L≤400, and an associated likelihood for cosmological parameter constraints. We find good agreement between our measurement of the lensing potential power spectrum and that found in the ΛCDM model that best fits the Planck temperature and polarization power spectra. Using the lensing likelihood alone we obtain a percent-level measurement of the parameter combination σ8Ω0.25 m = 0.591 ± 0.021. We combine our determination of the lensing potential with the E-mode polarization, also measured by Planck, to generate an estimate of the lensing B-mode. We show that this lensing B-mode estimate is correlated with the B-modes observed directly by Planck at the expected level and with a statistical significance of 10σ, confirming Planck’s sensitivity to this known sky signal. We also correlate our lensing potential estimate with the large-scale temperature anisotropies, detecting a cross-correlation at the 3σ level, as expected because of dark energy in the concordance ΛCDM model.

 

TG would not even look at the 1922 observation in WA so he is nearly a century behind. He thinks Eddington did nothing and the questions raised went unanswered. The WA observation answered any questions.

 

Our divine friend sees all of 21st century cosmology as wrong, hence his threads eventually being moved.
It's really just too silly for words. A shame how an inflated ego can course such blinkering of knowledge.

 

Achromatics ; by gravity gives no info or very little info to the star being lensed.

Respond to my post # 888 pad.

 

Perhaps I'm scared to answer river

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Or perhaps I know where any answer will lead to....

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Actually your question makes no sense in relation to this thread.
But a few facts for you.......
[1]Gravity is curved spacetime in the presence of mass.
[2]Light follows geodesics in that same curved spacetime.
[3] We see the fact that light follows geodesics in curved spacetime as gravitational lensing.
[4] Gravitational lensing is achromatic.
[5]Any refraction/deflection of that light by any medium is chromatic.
[6] Our very clever cosmologists and scientists are able to ascertain both if present and do that quite accurately.
[7]Gravitational lensing other than by a distant star, is also caused by galaxies, Quasars, DM, BH's and even ringed like systems such as our Kuiper Belt as detailed in the arXiv paper just up there a bit.
Or don't you read scientific papers river?
I mean many times you are asking questions, claiming I have not answered them, when the details are in papers, links and such.
Is this your example of an open mind?
Oh, and here's the paper for you in case you can't find it...plenty of others also!

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http://arxiv.org/pdf/1601.03051v1.pdf