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."
So "light falls" and "its energy should increase by exactly the same fraction that it increases for any other thing we could imagine dropping". This means that light just speeds up, like any falling body:
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."
However Cox and Forshaw know that the lie should always be "one leap ahead of the truth". Light does fall like material bodies, its energy does increase in an analogous manner, but its speed does not increase, only the speed of material bodies increases, the speed of light does not change at all, no it doesn't, how could it change, why should it change, who says it changes, Divine Einstein, yes we all believe in relativity, relativity, relativity.