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Thread: Gravitational deflection of light - measurements

  1. #61
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    Quote Originally Posted by Hetman View Post
    Thanks a lot.

    But according to the drawing, the image of the star, as seen from Venus, should be shifted by a missing angle to full deflection for Venus, which is half of the 1.7'', right?
    No, the angular position of the star as seen from Venus in this arrangement would be virtually equal to what the charted observer would see if we could somehow turn off the Sun's gravity. As I have said previously, the rays from the star are virtually parallel.
    And now I have a new problem.

    The deflection is an illusion, or whether there actually runs something along the arc instead of straight?

    I checked this using the Shapiro delay (for straight ray).
    Delay:

    and in terms of distance: z(r) = -cdt

    Direction of the wavefront tarns:
    tan a = dz/dr, for small angles: tan a = ~ a



    Thus, the rays run straight, only the wavefront rotates due to the diversity of delays.
    Similarly, stellar aberration - here the wavefront turns by a fixed angle of ~ v/c, and we see the images moved forward.

    Conclusion: we can not observe the stars below the edge of the Sun.
    No, we can in theory observe stars whose undeflected positions are up to 1.7" below the edge if we can eliminate the Sun's glare. If we could make the Sun's gravity strong enough, we could observe a star right on the center line. Its light would be refracted arould the edge all around and we would see a ring of light surrounding the massive body.

    As I understand it, general relativity predicts that anything whizzing by the Sun on a grazing path, whether bullets or photons, will be deflected. The burden is on you to show a convincing reason for us to think your model is better.

  2. #62
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    Quote Originally Posted by Hornblower View Post
    No, we can in theory observe stars whose undeflected positions are up to 1.7" below the edge if we can eliminate the Sun's glare. If we could make the Sun's gravity strong enough, we could observe a star right on the center line. Its light would be refracted arould the edge all around and we would see a ring of light surrounding the massive body.
    I think probably not - we do not observe the central image (means directly on the lens), only the ring around, or several images, typically two images, on the sides - never in the center of the lens.

    Although in optics are known cases of observing full images of obscured objects, then only the brightness decreases.


    Quote Originally Posted by Hornblower View Post
    As I understand it, general relativity predicts that anything whizzing by the Sun on a grazing path, whether bullets or photons, will be deflected. The burden is on you to show a convincing reason for us to think your model is better.
    I think this is the same, only dealt with the wave model of light, which is slightly more general than Newton's corpuscular model, or Einstein (QM is also based on the waves (wave functions); here prevails just a different terminology, and these interpretations, which are essentially superfluous and irrelevant, except perhaps some educational role).

  3. #63
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    Quote Originally Posted by Hetman View Post
    I think probably not - we do not observe the central image (means directly on the lens), only the ring around, or several images, typically two images, on the sides - never in the center of the lens.
    I never said we would see any starlight in the center. When I said "a star right on the center line", I was referring to its true position where we would see it in the absence of obstruction or gravitational lensing. Of course we would see nothing inside the edge of the occulting body.

    Although in optics are known cases of observing full images of obscured objects, then only the brightness decreases.




    I think this is the same, only dealt with the wave model of light, which is slightly more general than Newton's corpuscular model, or Einstein (QM is also based on the waves (wave functions); here prevails just a different terminology, and these interpretations, which are essentially superfluous and irrelevant, except perhaps some educational role).
    I cannot ascertain your line of thought from this sentence. Is there any way you could upload and post a sketch? Once again pictures sometimes help. That is why I posted pictures to back up my words.

  4. #64
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    Quote Originally Posted by Hornblower View Post
    snip...
    Of course we would see nothing inside the edge of the occulting body.

    ....snip
    Let me revise that for clarity. Of course we would not see any light that appeared to be coming from inside the edge. Everything from behind the occulting body would appear to be outside the edge.

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    Quote Originally Posted by Hornblower View Post
    I never said we would see any starlight in the center. When I said "a star right on the center line", I was referring to its true position where we would see it in the absence of obstruction or gravitational lensing. Of course we would see nothing inside the edge of the occulting body.
    But if the light were running on curved paths, then these images on the lenses have to be observed.
    In this version there are no constraints, the light could even run around, so you can see yourself from behind, and in the center of a distant galaxy.
    Last edited by pzkpfw; 2012-Mar-29 at 12:54 AM. Reason: Restore deleted text

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    Quote Originally Posted by Hornblower View Post
    I never said we would see any starlight in the center. When I said "a star right on the center line", I was referring to its true position where we would see it in the absence of obstruction or gravitational lensing. Of course we would see nothing inside the edge of the occulting body.
    But if the light were running on curved paths, then these images on the lenses have to be observed.
    In this version there are no restrictions, the light could even run around, so you could see yourself from behind, and in the center of a distant galaxy.

  7. #67
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    Quote Originally Posted by Hetman View Post
    But if the light were running on curved paths, then these images on the lenses have to be observed.
    In this version there are no constraints, the light could even run around, so you can see yourself from behind, and in the center of a distant galaxy.
    What do you mean by "images on the lenses" and what does it have to do with images of stars behind the Sun? I cannot visualize what you are trying to describe.

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    Quote Originally Posted by Hornblower View Post
    What do you mean by "images on the lenses" and what does it have to do with images of stars behind the Sun? I cannot visualize what you are trying to describe.
    You drew an example of such situation:
    http://img580.imageshack.us/img580/8127/docu0279.jpg
    Here Venus is completely covered by the Sun, and the star even better.

    In the case of perfectly symmetrical a ring is formed, but then it would be enough to straighten the rays of light from any direction (by setting the second mass next to the trajectory of rays) and you have an image in the center of the lens, plus the ring.
    Are known such cases? I think not.

    I checked several additional circumstances and it appears that the wave version of gravitational lenses explains many other interesting things, including cosmological redshift.
    Delays are cumulative, so the wavefront gradually turns, and that's enough.

    Or strong lenses on galaxy clusters: set the several galaxies in one line and you get huge effect, because the light goes straight there, so it passes close to all subsequent galaxies.

    With standard version rays deviate from the course on the first galaxy, so the final effect would be weak (in this version you need a lot of invisible matter).
    Last edited by Hetman; 2012-Mar-29 at 01:04 AM.

  9. #69
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    Quote Originally Posted by Hetman View Post
    You drew an example of such situation:
    http://img580.imageshack.us/img580/8127/docu0279.jpg
    Here Venus is completely covered by the Sun, and the star even better.
    Venus and the star would be hidden from the observer if there were no gravitational lensing. This is a sketch of the hypothetical case in which the star and Venus would be just visible, appearing to touch the limb of the Sun, if they were bright enough to be seen through the glare.
    In the case of perfectly symmetrical a ring is formed, but then it would be enough to straighten the rays of light from any direction (by setting the second mass next to the trajectory of rays) and you have an image in the center of the lens, plus the ring.
    Are known such cases? I think not.
    What second mass? Where is it supposed to be? Can you post a sketch? Your words are going nowhere that my feeble brain can grasp.
    I checked several additional circumstances and it appears that the wave version of gravitational lenses explains many other interesting things, including cosmological redshift.
    Delays are cumulative, so the wavefront gradually turns, and that's enough.

    Or strong lenses on galaxy clusters: set the several galaxies in one line and you get huge effect, because the light goes straight there, so it passes close to all subsequent galaxies.

    With standard version rays deviate from the course on the first galaxy, so the final effect would be weak (in this version you need a lot of invisible matter).
    Can you walk us through the analysis and calculations by mainstream astrophysicists and cosmologists that led to peer-reviewed papers on this topic, in appropriate mathematical detail?

    Can you compare their models side by side with yours, in appropriate mathematical detail?

    Can you make a convincing case that your model works better on observations that have been achieved?

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    Quote Originally Posted by Hetman View Post
    In the case of perfectly symmetrical a ring is formed, but then it
    would be enough to straighten the rays of light from any direction
    (by setting the second mass next to the trajectory of rays) and
    you have an image in the center of the lens, plus the ring.
    Are known such cases? I think not.
    The Sun's angular diameter is too large and its mass is too low
    for us to see a ring. If the Sun were much farther away, smaller,
    and / or more massive, we would see a ring when a sufficiently
    bright object was at the right distance behind the Sun. There
    would of course not be any central image.

    When galaxy clusters cause gravitational lensing, a central
    image of the distant object would be possible, but in practice
    the lensed arcs are visible because the light is concentrated,
    and direct light from the distant object is too faint to see
    through the center of the cluster, even if the line of sight
    happened to be clear.

    So in no case would I expect an image in the center, ever.

    I believe that complete rings have been seen many times.
    Partial rings have certainly been seen many times.

    -- Jeff, in Minneapolis
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    Quote Originally Posted by Hornblower View Post
    Venus and the star would be hidden from the observer if there were no gravitational lensing. This is a sketch of the hypothetical case in which the star and Venus would be just visible, appearing to touch the limb of the Sun, if they were bright enough to be seen through the glare.
    I understand, but such a direct calculation of lights' trajectories are probably incompatible with the principles of optics.

    The observed image is always formed due to the superposition of many waves (Huygens' principle), creating a wavefront, which determines the position of the observed image.

    The path of rays (tangent to it) is just the direction perpendicular to the instantaneous line of wavefront.
    In fact, nothing runs along the curve (this is only a suggestion - pure intuition).

    Quote Originally Posted by Hornblower View Post
    Can you walk us through the analysis and calculations by mainstream astrophysicists and cosmologists that led to peer-reviewed papers on this topic, in appropriate mathematical detail?

    Can you compare their models side by side with yours, in appropriate mathematical detail?

    Can you make a convincing case that your model works better on observations that have been achieved?
    I rather do not plan to analyze the work in this area - they are too inaccurate, wishful thinking, based on many assumptions (commonly known).

    Corpuscular models are just a gross oversimplification, the domain of application is usually small, marginal.
    There is no doubt that the theory of waves definitively solve these problems, as it was many times in other areas.

    http://einstein.stanford.edu/Library.../cl0024big.gif
    http://einstein.stanford.edu/SPACETIME/spacetime3.html

    The observations are quite clear: the required exotic dark matter has a density some five times that of standard-model matter, and the required dark energy has an energy density some three times greater still.
    The concentration of galaxies, which can be seen in the center, is enough to produce this effect.
    Here the images are just shifted from the center, not a running light from a distant galaxy (lensed).
    Last edited by PetersCreek; 2012-Mar-29 at 03:56 PM. Reason: Converted oversize image to link (Rule 8)

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    Hetman, your thread has been moved into ATM, which means you have to defend your view of things, not to question mainstream physics (please read the rules of ATM, linked in my signature). Please show where mainstream is wrong in detail and show how your ideas are correct in detail. Up to now you have not brought any convincing evidence that the observed gravitational bending of light is incorrect.
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  13. #73
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    I just noticed, first, almost entirely by accident, delays already generate full deflection: 4GM / c ^ 2r, so already there is no room for bending the trajectory of rays, because then it would be together two times too much.

    In this area, the term 'trajectory of light' is already inadequate - perhaps this is a cardinal error.

    Immediately afterwards, I noticed that the direct calculation of the trajectories of light, seen as a stream of particles - photons, is an old mistake - with the great tradition, reproduced systematically in many phenomena and situations, and already well known for many years in optics and quantum physics.

    Young's experiment, and many similar, were known in 1919, and before, so improvisations with a trajectories of photons in gravity have been and are useless.

  14. #74
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    Quote Originally Posted by Hetman View Post
    I just noticed, first, almost entirely by accident, delays already generate full deflection: 4GM / c ^ 2r, so already there is no room for bending the trajectory of rays, because then it would be together two times too much.
    I find it rather interesting that you knew about the Shapiro delay and made a presumably accurate calculation of the skewing of the wavefront, but at the same time had a basic misunderstanding of the geometry of the situation. I find by looking at a simple sketch that bending the rays so they stay perpendicular to the wavefront does not introduce any significant discrepancy, let alone double anything.

    In this area, the term 'trajectory of light' is already inadequate - perhaps this is a cardinal error.

    Immediately afterwards, I noticed that the direct calculation of the trajectories of light, seen as a stream of particles - photons, is an old mistake - with the great tradition, reproduced systematically in many phenomena and situations, and already well known for many years in optics and quantum physics.

    Young's experiment, and many similar, were known in 1919, and before, so improvisations with a trajectories of photons in gravity have been and are useless.
    Once again, we challenge you to do the following:

    1. Walk us through the general relativity model, step by step, in appropriate mathematical detail.

    2. Walk us through your alternative model, step by step, in appropriate mathematical detail.

    3. Compare them side by side and compare the predictions of each one with well documented observations.

    4. Show us which one fits the observations better.

    If you do not do this, for whatever reason, then I find no choice but to disregard your idea as not having scientific merit.

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    Quote Originally Posted by Hornblower View Post
    I find it rather interesting that you knew about the Shapiro delay and made a presumably accurate calculation of the skewing of the wavefront, but at the same time had a basic misunderstanding of the geometry of the situation. I find by looking at a simple sketch that bending the rays so they stay perpendicular to the wavefront does not introduce any significant discrepancy, let alone double anything.
    Here differences of delays are crucial (precisely: gradient of delays on illuminated surface).
    This gradient practically don't depend on the trajectory.

    Quote Originally Posted by Hornblower View Post
    Once again, we challenge you to do the following:

    1. Walk us through the general relativity model, step by step, in appropriate mathematical detail.

    2. Walk us through your alternative model, step by step, in appropriate mathematical detail.

    3. Compare them side by side and compare the predictions of each one with well documented observations.

    4. Show us which one fits the observations better.

    If you do not do this, for whatever reason, then I find no choice but to disregard your idea as not having scientific merit.
    I don't have time for complex analyzes and calculations.

    In clusters of galaxies we get several times larger displacement of images and they are also highly redshifted (these two effects are proportional here).

    In simple cases, the result is identical (except for images of covered sources, which is anyway unverifiable).
    Last edited by Hetman; 2012-Mar-31 at 01:56 AM.

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    Quote Originally Posted by Hetman View Post
    I don't have time for complex analyzes and calculations.
    In other words, you really don't have any kind of support for your assertions.

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    Quote Originally Posted by Hetman View Post
    I don't have time for complex analyzes and calculations.
    Maybe you need to make the time.

    The default for these threads is 30 days. If you are making a good faith effort to discuss your idea and work on things, and need more time, ask and we will probably give an extension. But if you are not going to make a good faith effort to address these questions, we can just close this thread now.
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  18. #78
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    Quote Originally Posted by Tensor View Post
    In other words, you really don't have any kind of support for your assertions.
    Excuse me, but I have not heard that it was necessary to prove the proof.

    I showed already how and why the wavefront is turning due to the delays - in accordance with GR.

    So, now probably you should show that the deflection of rays eliminates the twist of the wavefront, correctly?

    Or maybe you are suggesting that it is possible to see the image in the direction inconsistent with the direction of wave front - yes?
    It is impossible. Image emerges in the direction normal (perpendicular) to the wavefront.

  19. #79
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    Quote Originally Posted by Hetman View Post
    Excuse me, but I have not heard that it was necessary to prove the proof.

    I showed already how and why the wavefront is turning due to the delays - in accordance with GR.

    So, now probably you should show that the deflection of rays eliminates the twist of the wavefront, correctly?

    Or maybe you are suggesting that it is possible to see the image in the direction inconsistent with the direction of wave front - yes?
    It is impossible. Image emerges in the direction normal (perpendicular) to the wavefront.
    To quote Hornblower:

    Once again, we challenge you to do the following:

    1. Walk us through the general relativity model, step by step, in appropriate mathematical detail.

    2. Walk us through your alternative model, step by step, in appropriate mathematical detail.

    3. Compare them side by side and compare the predictions of each one with well documented observations.

    4. Show us which one fits the observations better.

    If you do not do this, for whatever reason, then I find no choice but to disregard your idea as not having scientific merit.

    If you decide you don't have the time, that's your decision. If you decide you don't have the time, you simply have not shown your idea has any scientific merit, it's that simple. Your choice.

  20. #80
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    It is time for me to bolster my remarks with some more sketches.

    Figure 1
    http://img11.imageshack.us/img11/3773/docu0282.jpg

    This shows my understanding of the bending of a narrow beam that is grazing the Sun. Of course the width of the beam is exaggerated here. We are talking about a beam as wide as the camera lens, which is tiny compared to the radius of the Sun.

    Figure 2
    http://img96.imageshack.us/img96/1509/docu0283.jpg

    This is my interpretation of what Hetman posted in which he argues that the wavefronts become slanted as they pass the Sun, but the rays marking the edges of the beam remain straight. Hetman, if you think I misconstrued what you said, please speak up.

    Let's assume for the purpose of argument that Hetman's Shapiro delay calculations that gave the wavefront slant are accurate. For these small angles it does not matter whether we curve the rays as in Figure 1 or leave them straight as in figure 2. Either way the slant of the wavefronts remains virtually the same.

    Hetman, what if anything do you think I am missing here?

  21. #81
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    In fact, in Hornblower's diagrams, if the beam is so narrow in
    comparison to the distance to the Sun's center that the bending
    of the top edge is the same as the bending of the bottom edge,
    then the delay is identical for the two edges. If the beam is
    wide enough for the delay to be different, then the bending is
    also different by the same proportion.

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  22. #82
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    I am following up on my previous post with more details, since I know I was cutting some corners. Letís see if I introduced any significant error by doing so.

    Let us start with a hypothetical case with the light rays passing 1 billion meters from the center of the massive body, and being deflected 1 arcsecond. This is fairly close to the actual numbers for the Sun, and it gives us nice round numbers to crunch. Letís have the upper and lower rays coming in parallel, 1 meter apart. For the purpose of this exercise we treat photons coming in along these rays as marking the end points of wavefronts, sort of like soldiers marching in ranks perpendicular to the route. (During 32 years with a military band, I did this zillions of times.)

    In Hetmanís model, illustrated in figure 2 as I think I understand it, the rays remain straight as they pass the Sun. The photon on the lower ray undergoes slightly more Shapiro delay than its partner on the upper ray. Letís assume for the purpose of this exercise that Hetmanís calculation of this difference is accurate. The difference in the amount of setback by the time they are well clear of the Sun is about 5 microns, which rotates the wavefront by 1 arcsecond from the original vertical. Hetman appears to be asserting that these wavefronts continue to follow a straight path, and that their slant results in a deflected image within a camera.

    In figure 1 I am showing the curving paths of the rays as I think I understand the mainstream model. Since the ultimate deflection angle is inversely proportional to the minimum distance from the center of the Sun, the upper ray is deflected about a billionth of an arcsecond less than the lower one. By the time the rays reach Earth they have diverged less than a millimeter from their original spacing of 1 meter, so they can be regarded as remaining parallel. Assuming the same 5 microns of difference in Shapiro delay along the rays as in Hetmanís model, we find virtually the same 5 microns of difference in the horizontal components of these displacements at such small angles. Even in the vastly larger deflection in my sketch there is very little discrepancy. Thus the wavefronts are slanted virtually the same amount in both models. In my model they remain perpendicular to the rays throughout.

    I am not asserting that the act of modeling a wavefront as a string of photons resembling soldiers in ranks is a physically rigorous exercise in light wave mechanics. My sole purpose is a geometric rebuttal of Hetmanís apparent assertion that allowing the rays to bend as in figure 1 would double something about the wavefront slant.

    As always, Jeff's remarks were most welcome and prompted me to pay closer attention to details.

  23. #83
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    Quote Originally Posted by Hornblower View Post
    It is time for me to bolster my remarks with some more sketches.

    Figure 1
    http://img11.imageshack.us/img11/3773/docu0282.jpg

    This shows my understanding of the bending of a narrow beam that is grazing the Sun. Of course the width of the beam is exaggerated here. We are talking about a beam as wide as the camera lens, which is tiny compared to the radius of the Sun.

    Figure 2
    http://img96.imageshack.us/img96/1509/docu0283.jpg

    This is my interpretation of what Hetman posted in which he argues that the wavefronts become slanted as they pass the Sun, but the rays marking the edges of the beam remain straight. Hetman, if you think I misconstrued what you said, please speak up.

    Let's assume for the purpose of argument that Hetman's Shapiro delay calculations that gave the wavefront slant are accurate. For these small angles it does not matter whether we curve the rays as in Figure 1 or leave them straight as in figure 2. Either way the slant of the wavefronts remains virtually the same.

    Hetman, what if anything do you think I am missing here?
    That's right. The direction of rays is consistent with the direction of the wavefront.

    But I'm afraid it does not change anything - just that is the definition of these rays, ie geodetic lines.
    In fact, here goes nothing along those lines - these are just the directions normal to the wavefronts!

    The waves are running spherically from the source, and if there are no obstacles on the way to the receiver, then there is no reason to believe that here the direction of propagation changes.
    The direction will change only in remission, ie the interaction is required - contact with matter!

    http://alienryderflex.com/refraction/

    Besides, I wonder why not take account of the ordinary refraction in matter around the sun or other stars.
    For example, white dwarfs apparently have a very dense atmosphere, so it should significantly affect the observed image.

    The solar wind - low density, but it is very extensive.
    Some stars emit many times more matter. Galaxies probably even more (proportionally).

    Refractive index for such an expanding sphere of gas should be of the form:
    n = 1 + k/r^2, because of the density distribution of 1/r^2, closer to the star;
    and further: 1/r^3/2, 1/r, etc.

    What will be the deflection of light for such a refractive index?

    I try to calculate this using the same method:

    then deflection:


    The second term vanishes for large distances x >> R, so we get full deflection: a = k 2 pi/2/R ^ 2 = k pi / R ^ 2;
    k - a constant that depends on the density of the gas.


    Thus, we obtain the deflection about 1'' for n(R) = 1 + 1e-6 (at the surface of the star).
    Last edited by Hetman; 2012-Apr-05 at 02:15 PM.

  24. #84
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    Quote Originally Posted by Hetman View Post
    That's right. The direction of rays is consistent with the direction of the wavefront.

    But I'm afraid it does not change anything - just that is the definition of these rays, ie geodetic lines.
    In fact, here goes nothing along those lines - these are just the directions normal to the wavefronts!

    The waves are running spherically from the source, and if there are no obstacles on the way to the receiver, then there is no reason to believe that here the direction of propagation changes.
    The direction will change only in remission, ie the interaction is required - contact with matter!

    http://alienryderflex.com/refraction/

    Besides, I wonder why not take account of the ordinary refraction in matter around the sun or other stars.
    For example, white dwarfs apparently have a very dense atmosphere, so it should significantly affect the observed image.

    The solar wind - low density, but it is very extensive.
    Some stars emit many times more matter. Galaxies probably even more (proportionally).

    Refractive index for such an expanding sphere of gas should be of the form:
    n = 1 + k/r^2, because of the density distribution of 1/r^2, closer to the star;
    and further: 1/r^3/2, 1/r, etc.

    What will be the deflection of light for such a refractive index?

    I try to calculate this using the same method:

    then deflection:


    The second term vanishes for large distances x >> R, so we get full deflection: a = k 2 pi/2/R ^ 2 = k pi / R ^ 2;
    k - a constant that depends on the density of the gas.


    Thus, we obtain the deflection about 1'' for n(R) = 1 + 1e-6 (at the surface of the star).
    I am posting this primarily for the benefit of the readership at large.

    An excerpt from Hetman's post #73:

    Quote Originally Posted by Hetman
    I just noticed, first, almost entirely by accident, delays already generate full deflection: 4GM / c ^ 2r, so already there is no room for bending the trajectory of rays, because then it would be together two times too much.
    I responded by posting sketches in which I found no such discrepancy, and asked him what, if anything, he thought I might be missing. No explicit answer that makes any sense to me has been forthcoming. His mathematical display in the latest post may look impressive to a novice, but I see it as merely digressing into refractions in hypothetical masses of gas, rather than sticking to my questions about his take on purely gravitational lensing. I am not bothering to check out the accuracy of the math because I consider it to be irrelevant to my questions.

    My confidence in my reasoning as expressed in my previous posts remains unshaken. I rest my case, with the option of reopening it should Hetman come up with something that is more convincing.

  25. #85
    Join Date
    Mar 2012
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    But I said you're right.

    I just think that this popular procedure, which involves calculating the trajectories of some particles of light in gravity is highly questionable.

  26. #86
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    Quote Originally Posted by Hetman View Post
    But I said you're right.

    I just think that this popular procedure, which involves calculating the trajectories of some particles of light in gravity is highly questionable.
    But that is what we are trying to address--your reasons for thinking it is questionable. If you can't defend your reasons...the thread will have to be closed.

  27. #87
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    I doubt anyone could argue that some clever photons run through some lines in order to minimize time of flight to an unknown observer.

    Therefore, there no other choice, except that the simplest: a light propagates through straight lines along which we calculate the delay times, and then bending angle and geodesic lines, and not vice versa!

    The consequences are obvious:
    when we have a few galaxies placed along one line, then we get a much higher delays, the sum of the delays, and hence the illusion of the presence of invisible matter in massive quantities.

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