# Speed of Light in Gravity : Newton? Einstein?

#### Pentcho Valev

As light falls in a gravitational field, what happens to its speed?

The Newtonian prediction is straightforward (it is so obviously true that even Einsteinians teach it explicitly):

James Hartle, Gravity: An Introduction to Einstein's General Relativity, p. 113: "If we accept the equivalence principle, we must also accept that light falls in a gravitational field with the same acceleration as material bodies." https://www.amazon.com/Gravity-Introduction-Einsteins-General-Relativity/dp/0805386629

Paul A. Tipler, Ralph A. Llewellyn, Modern Physics: "To see why a deflection of light would be expected, consider Figure 2-17, which shows a beam of light entering an accelerating compartment. Successive positions of the compartment are shown at equal time intervals. Because the compartment is accelerating, the distance it moves in each time interval increases with time. The path of the beam of light, as observed from inside the compartment, is therefore a parabola. But according to the equivalence principle, there is no way to distinguish between an accelerating compartment and one with uniform velocity in a uniform gravitational field. We conclude, therefore, that A BEAM OF LIGHT WILL ACCELERATE IN A GRAVITATIONAL FIELD AS DO OBJECTS WITH REST MASS. For example, near the surface of Earth light will fall with acceleration 9.8 m/s^2." http://web.pdx.edu/~pmoeck/books/Tipler_Llewellyn.pdf

University of Illinois at Urbana-Champaign: "Consider a falling object. Its speed increases as it is falling. Hence, if we were to associate a frequency with that object the frequency should increase accordingly as it falls to earth. Because of the equivalence between gravitational and inertial mass, we should observe the same effect for light. So lets shine a light beam from the top of a very tall building. If we can measure the frequency shift as the light beam descends the building, we should be able to discern how gravity affects a falling light beam. This was done by Pound and Rebka in 1960. They shone a light from the top of the Jefferson tower at Harvard and measured the frequency shift. The frequency shift was tiny but in agreement with the theoretical prediction." https://courses.physics.illinois.edu/phys419/sp2011/lectures/Lecture13/L13r.html

The Einsteinian prediction? As light falls in a gravitational field, what happens to its speed, according to general relativity? Normally, scientists couldn't care less (post-truth science), but if someone does care and starts searching the Internet, he/she will find...no answer. There are no authoritative sources discussing the issue. A few apparently marginal sources suggest that, according to general relativity, the speed of falling light, unlike the speed of ordinary falling objects, DECREASES. The language in these marginal sources is confusing and contradictory, so citing them is useless, if not counterproductive.

Einstein himself has repeated countless times that the speed of light varies in a gravitational field, but never explained how it varies. Something is rotten in the state of Denmark, isn't it?

#### Pentcho Valev

Albert Einstein: "The gravitational force bends the light ray as if light were a catapulted heavy body. This consequence is of great significance in a twofold way. First... [...] Second, this consequence shows that the law of the constancy of the speed of light no longer holds, according to the general theory of relativity, in spaces that have gravitational fields. As a simple geometric consideration shows, the curvature of light rays occurs only in spaces where the speed of light is spatially variable." https://einsteinpapers.press.princeton.edu/vol7-trans/155

So, according to Einstein, bending of light shows that the speed of light varies in a gravitational field. But what precisely does bending show? As light falls towards the source of gravity, its speed increases or decreases? Neither Einstein nor any high priest in the Einstein Cult would answer this question.

Yet the question has an obvious answer, so obvious that ordinary Einsteinians often leave Einstein's schizophrenic world for a while and tell the truth. Bending shows that the speed of falling light INCREASES as per Newton:

"To see WHY A DEFLECTION OF LIGHT WOULD BE EXPECTED, consider Figure 2-17, which shows a beam of light entering an accelerating compartment. Successive positions of the compartment are shown at equal time intervals. Because the compartment is accelerating, the distance it moves in each time interval increases with time. The path of the beam of light, as observed from inside the compartment, is therefore a parabola. But according to the equivalence principle, there is no way to distinguish between an accelerating compartment and one with uniform velocity in a uniform gravitational field. We conclude, therefore, that A BEAM OF LIGHT WILL ACCELERATE IN A GRAVITATIONAL FIELD AS DO OBJECTS WITH REST MASS. For example, near the surface of Earth light will fall with acceleration 9.8 m/s^2." http://web.pdx.edu/~pmoeck/books/Tipler_Llewellyn.pdf

Why are high priests in the Einstein Cult adamantly silent in this particular case? Because Einstein's general relativity predicts that the speed of falling light DECREASES, and this is so preposterous that the hypnotised scientific community may suddenly wake up and then...lasciatemi morire:

#### Atlan0001

Look at any light time history (light time information) et all. It will tell you immediately that the constant of the speed of light, 'c', is the only straight-line information from there to here in the universe. The line of information within, every line of history within, every line of light time history within, will tell you that . . . line straight ('c') as straight-line can get ('c') and forthwith. The proof is [in] the pudding, as the saying goes.

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