http://arxiv.org/pdf/gr-qc/9909014v1.pdf Steve Carlip: "It is well known that the deflection of light is twice that predicted by Newtonian theory; in this sense, at least, light falls with twice the acceleration of ordinary "slow" matter."
A joke? No. Steve Carlip is more than serious - this is exactly what Divine Albert's Divine Theory predicts:
http://www.speed-light.info/speed_of_light_variable.htm "Einstein wrote this paper in 1911 in German. (...) ...you will find in section 3 of that paper Einstein's derivation of the variable speed of light in a gravitational potential, eqn (3). The result is: c'=c0(1+phi/c^2) where phi is the gravitational potential relative to the point where the speed of light co is measured. (...) You can find a more sophisticated derivation later by Einstein (1955) from the full theory of general relativity in the weak field approximation. (...) Namely the 1955 approximation shows a variation in km/sec twice as much as first predicted in 1911."
http://www.mathpages.com/rr/s6-01/6-01.htm "Specifically, Einstein wrote in 1911 that the speed of light at a place with the gravitational potential phi would be c(1+phi/c^2), where c is the nominal speed of light in the absence of gravity. In geometrical units we define c=1, so Einstein's 1911 formula can be written simply as c'=1+phi. However, this formula for the speed of light (not to mention this whole approach to gravity) turned out to be incorrect, as Einstein realized during the years leading up to 1915 and the completion of the general theory. (...) ...we have c_r =1+2phi, which corresponds to Einstein's 1911 equation, except that we have a factor of 2 instead of 1 on the potential term."
So we have doublethink in Big Brother's world but triplethink in Divine Albert's world: In a gravitational field the speed of light is (1) constant, (2) just as variable as the speed of ordinary falling objects and (3) twice as variable as the speed of ordinary falling objects. (3) has already been demonstrated; here are some examples of (1) and (2):
(1) In a gravitational field, the speed of light is constant:
http://www.amazon.com/Why-Does-mc2-Should-Care/dp/0306817586 Brian Cox, Jeff Forshaw, p. 236: "If the light falls in strict accord with the principle of equivalence, then, as it falls, its energy should increase by exactly the same fraction that it increases for any other thing we could imagine dropping. We need to know what happens to the light as it gains energy. In other words, what can Pound and Rebka expect to see at the bottom of their laboratory when the dropped light arrives? There is only one way for the light to increase its energy. We know that it cannot speed up, because it is already traveling at the universal speed limit, but it can increase its frequency."
http://helios.gsfc.nasa.gov/qa_sp_gr.html Dr. Eric Christian: "Is light affected by gravity? If so, how can the speed of light be constant? Wouldn't the light coming off of the Sun be slower than the light we make here? If not, why doesn't light escape a black hole? Yes, light is affected by gravity, but not in its speed. General Relativity (our best guess as to how the Universe works) gives two effects of gravity on light. It can bend light (which includes effects such as gravitational lensing), and it can change the energy of light. But it changes the energy by shifting the frequency of the light (gravitational redshift) not by changing light speed. Gravity bends light by warping space so that what the light beam sees as "straight" is not straight to an outside observer. The speed of light is still constant."
http://faculty.ucmerced.edu/dkiley/Physics161GravRedshift.pdf "The frequency depends on the acceleration, which we have chosen to be a = g, the acceleration due to gravity on Earth. If we ignore the derivation of this equation, and just look at the result, then we would be led to believe that a beam of light just traveling upwards in a gravitational field would lose frequency! This is, in fact, completely true. Light is affected by gravity, and as light tries to escape from a gravitational field it experiences a redshift, causing its frequency to decrease (hence becoming redder). We can think of this in another (classical) way. When we throw a ball up into the air, it slows down, using it's kinetic energy to do work against the force of gravity. Light has to do work against gravity, too, but it can't change it speed. Therefore it has to lose energy, not by losing speed, but by losing frequency, since the energy of light depends on its frequency. This follows directly from Einstein's Theory of General Relativity, which says that acceleration and gravity are equivalent."
http://www.oapt.ca/newsletter/2004-02%20Newsletter%20Searchable.pdf Richard Epp: "One may imagine the photon losing energy as it climbs against the Earth's gravitational field much like a rock thrown upward loses kinetic energy as it slows down, the main difference being that the photon does not slow down; it always moves at the speed of light."
http://www.youtube.com/watch?v=ixhczNygcWo "The light is perceived to be falling in a gravitational field just like a mechanical object would. (...) The change in speed of light with change in height is dc/dh=g/c."
Both (1) and (2): In a gravitational field, the speed of light is both variable and constant, Divine Einstein, yes we all believe in relativity, relativity, relativity:
http://math.ucr.edu/home/baez/physics/Relativity/SpeedOfLight/speed_of_light.html Steve Carlip: "Einstein went on to discover a more general theory of relativity which explained gravity in terms of curved spacetime, and he talked about the speed of light changing in this new theory. In the 1920 book "Relativity: the special and general theory" he wrote: "...according to the general theory of relativity, the law of the constancy of the velocity of light in vacuo, which constitutes one of the two fundamental assumptions in the special theory of relativity [...] cannot claim any unlimited validity. A curvature of rays of light can only take place when the velocity of propagation of light varies with position." Since Einstein talks of velocity (a vector quantity: speed with direction) rather than speed alone, it is not clear that he meant the speed will change, but the reference to special relativity suggests that he did mean so. This interpretation is perfectly valid and makes good physical sense, but a more modern interpretation is that the speed of light is constant in general relativity."