The top of a tower of height h emits light with (initial) frequency f, speed c and wavelength L. Observers on the ground (Pound and Rebka) measure the frequency to be f'=f(1+gh/c^2), the speed c' and the wavelength L'. Hypotheses:

A. Gravitational time dilation does exist.

B. There is no gravitational time dilation.

C. Photons do accelerate in a gravitational field.

D. Photons do not accelerate in a gravitational field.

E. c' = c(1+gh/c^2)

F. c' = c(1+2gh/c^2)

G. c' = c

H. L' = L/(1+gh/c^2)

I. L' = L

Even if we do not know which hypothesis is true and which false, we may still try to find consistent combinations which satisfy the formula:

(frequency) = (speed of light)/(wavelength)

In my view, consistent combinations a

A,D,E,I

B,C,E,I

B,D,G,H

Note that there is no consistent combination for F, the variation of the speed of light predicted by Einstein's general relativity.

Pentcho Valev