Why is the Gravitational Curving of Light now called 'Gravitational Lensing'?

[RascalPuff]

Bending light around a massive object from a distant source. The orange arrows show the apparent position of the background source. The white arrows show the path of the light from the true position of the source.
(Wikepedia)

The bending of light as it passes through Einstein's accelerating elevator is well known to students of General Relativity. The example was applied to the alteration of light paths during a total eclipse in Eddington's expedition of 1919, and was applauded as the first experimental proof of Einstein's prediction that gravity could curve light.


Since the time of Eddington's expedition many different settings for the observation of the alteration of light traveling nearby massive sources of gravitation have come to be called 'gravitational lensing': apparently because in order to attribute the curve of light to acceleration of a coordinate system (as it was in 1919), the massive system past which light travels would have to be recognized as accelerating, as they are in Einstein's elevator example(s). The former explanation of the curving of light has apparently been replaced by 'gravitational lensing', therefore, because, 'obviously the massive coordinate systems in consideration here, are not omnidirectionally expanding'.

Whereas, in accordance with Total Field Theory, the massive coordinate systems at point in this (above) consideration, are conceptualized as being in a state of constantly accelerating expansion, and are therefore responsible for the observed curvature of light.

Question:
Why has the explanation for the curvature of light (under the circumstances in point) changed from its original interpretation? Is it not due to the exclusion of the possibility that the entire coordinate near which it (light) is passing, 'obviously is not and could not be' in a state of constantly expanding acceleration?

[RascalPuff]

The bending of light as it passes through Einstein's accelerating elevator is well known to students of General Relativity. The example was applied to the alteration of light paths during a total eclipse in Eddington's expedition of 1919, and was applauded as the first experimental proof of Einstein's prediction that gravity could curve light.


Since the time of Eddington's expedition many different settings for the observation of the alteration of light traveling nearby massive sources of gravitation have come to be called 'gravitational lensing': apparently because in order to attribute the curve of light to acceleration of a coordinate system (as it was in 1919), the massive system past which light travels would have to be recognized as accelerating, as they are in Einstein's elevator example(s). The former explanation of the curving of light has apparently been replaced by 'gravitational lensing', therefore, because, 'obviously the massive coordinate systems in consideration here, are not omnidirectionally expanding'.

Whereas, in accordance with Total Field Theory, the massive coordinate systems at point in this (above) consideration, are conceptualized as being in a state of constantly accelerating expansion, and are therefore responsible for the observed curvature of light.

Question:
Why has the explanation for the curvature of light (under the circumstances in point) changed from its original interpretation? Is it not due to the exclusion of the possibility that the entire coordinate near which it (light) is passing, 'obviously is not and could not be' in a state of constantly expanding acceleration?

The below discourse is excerpted from http://www.nobeliefs.com/light.htm by Jim Walker, Dec. 1998 Copyright free.

According to Einstein's thought experiment on gravity, he imagined himself in an elevator feeling its acceleration upward. Einstein thought that since you cannot see outside the elevator, you cannot tell the difference between the force of gravity or an acceleration force (imagine the elevator in free space). Einstein proposed that the two forces appear equal. Furthermore, if a "ray" of light entered the elevator parallel to the floor, the light beam would appear to bend downward. This meant that light, if traveled across a gravitational field, would looked curved to the observer.
In 1919, the astronomer Sir Arthur Eddington photographed stars whose field of vision appeared close to the sun during an eclipse. He compared the photos with those of the same stars taken with the sun removed. Eddington found the apparent location of the stars had shifted, just as Einstein predicted and confirmed one of the predictions of the general theory of relativity.
But notice that even though Einstein believed in the discrete existence of quantum light, his description does not explicitly state that light gravitates. In his paper on The Foundation of the General Theory of Relativity he states: "We easily recognize that the course of the light-rays must be bent with regard to the system of co-ordinates..." (Einstein, 1916) . But to an observer at rest, the light beam would appear straight. In other words, Einstein gives a relativistic description, not a gravitating mechanism. The description further gets exacerbated by illustrations that show the Einstein bend in an exaggerated way:

This typical diagram shows the light bending in a dramatic but inaccurate way. Eddington measured a deflection of 1.75 seconds of arc (Einstein actually predicted .83 seconds of arc, but the measurement came close enough to confirm the theory). We can forgive the artist's exaggeration, however, because one cannot draw the actual arc and see it. The tiny angle, would result in, for all appearances, a straight line. Eddington's photos also had to capture stars at the closest periphery to the sun.
I do not pretend to have a solution for how light gives this bending illusion, but I can speculate:
Since Einstein's theory predicts a gravitational influence on the measurement of clocks, perhaps electrons at the solar edge, shift their spin orientation accordingly when acting as a reflector or defractor. How else can we think of curved space except for how matter behaves in it? Physicists also know that electrons can pop in and out of existence, even in a vacuum. In short, in order to observe this bend, you must have a mass to cause the deflection.
Note also, that a pixel moving across a screen while you watched from a gravitational well would also appear to bend even though we know the pixel does not actually move. (In Einstein's thought experiment, imagine looking outside the elevator at a large TV screen with a pixel trajectory instead of a beam of light).

Gravitational lens
Gravitational lensing can occur which can make stellar objects, (such as galaxies and quasars), appear doubled, magnified or focused. This seemingly odd phenomon actually implies a special case of Einstein bend, as described above, except that the deflection occurs on both sides of a mass.
Again, in order observe an Einstein shift or a gravitational lens effect, there must exist some material body to influence its relative observed position.

[RascalPuff]

The operative concept in this inquiry seems to be the distances and sizes of the systems that are effecting gravitational lensing - namely galaxies and quasars, rather than the individual stellar sources of light; refraction of light is also brought to bear in these specific considerations. The following excerpt is derived from Wikepedia's 'Gravitational lens':
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Wikimedia Commons has media related to: Gravitational lensingA gravitational lens is formed when the light from a very distant, bright source (such as a quasar) is "bent" around a massive object (such as a cluster of galaxies) between the source object and the observer. The process is known as gravitational lensing, and is one of the predictions of Albert Einstein's general theory of relativity.
Although Orest Chwolson is credited as being the first to discuss the effect in print (in 1924), the effect is more usually associated with Einstein, who published a more famous article on the subject in 1936.
Fritz Zwicky posited in 1937 that the effect could allow galaxy clusters to act as gravitational lenses. It was not until 1979 that this effect was confirmed by observation of the so-called "Twin QSO" SBS 0957+561.

[Bogie]

Hi RascalPuff, I have been interested in the phenomenon of curved light for awhile. I read Total Field Theory back in December when you posted a link to it from a thread at SciForums. You will remember me as Q_W there. Circumstance did not afford us an opportunity to get into this aspect of the TFT view but I understand the statement that current views of gravitational lensing are contrary to TFT because "obviously the universe is not in a state of constantly expanding acceleration". However, though TFT has a different explanation for the curvature of light passing near very massive objects, there are some aspects of light that are not addressed either by the 4-D expansion of space near objects or the gravitational effect on light. I speak of the effect that the medium through which light passes effects the speed of light.

Are you interested in addressing that issue? Perhaps you or others here at Toequest would be willing to talk this through with me to help me clear up any misconceptions I might have worked myself into. Let me quote Wiki for starters: http://en.wikipedia.org/wiki/Speed_of_light "The actual speed at which light propagates through transparent materials, such as glass or air, is less than c. The ratio between c and the speed v at which light travels in a material is called the refractive index n of the material (n = c / v). For example, for visible light the refractive index of glass is typically around 1.5, meaning that light in glass travels at c / 1.5 ≈ 200,000 km/s; the refractive index of air for visible light is about 1.0003, so the speed of light in air is very close to c."

And to be clear, I am operating from the perspective that the energy density surrounding massive objects like the sun or galaxies/galaxy clusters is significantly different than the energy density of deep space. If light travels slower through the higher energy density space surrounding massive objects then it would appear to bend. Is there any merit to that perspective?

[Bogie]

...
And to be clear, I am operating from the perspective that the energy density surrounding massive objects like the sun or galaxies/galaxy clusters is significantly different than the energy density of deep space. If light travels slower through the higher energy density space surrounding massive objects then it would appear to bend. Is there any merit to that perspective?

I drew a graphic to show the concept of how I am proposing that light is effected by a high energy density field ...