http://www.personal.kent.edu/~fwilli...Relativity.pdf
David Morin: "A light source on top of a tower of height h emits flashes at time intervals Ts. A receiver on the ground receives the flashes at time intervals Tr. What is Tr in terms of Ts?"

If bullets are shot downwards at time intervals Ts, the receiver on the ground will receive them at time intervals Tr=Ts. Yet David Morin's calculations show that, for light, TsTr. Are the calculations based on some implicit false assumption? They must be: Insofar as the speed variation in a gravitational field is concerned, the analogy between bullets and photons is straightforward:

http://sethi.lamar.edu/bahrim-cristi...t-lens_PPT.pdf
Dr. Cristian Bahrim: "If we accept the principle of equivalence, we must also accept that light falls in a gravitational field with the same acceleration as material bodies."

http://www.wfu.edu/~brehme/space.htm
Robert W. Brehme: "Light falls in a gravitational field just as do material objects."

http://www.einstein-online.info/spot...t_white_dwarfs
Albert Einstein Institute: "One of the three classical tests for general relativity is the gravitational redshift of light or other forms of electromagnetic radiation. However, in contrast to the other two tests - the gravitational deflection of light and the relativistic perihelion shift -, you do not need general relativity to derive the correct prediction for the gravitational redshift. A combination of Newtonian gravity, a particle theory of light, and the weak equivalence principle (gravitating mass equals inertial mass) suffices. (...) The gravitational redshift was first measured on earth in 1960-65 by Pound, Rebka, and Snider at Harvard University..."

http://www.youtube.com/watch?v=FJ2SVPahBzg
"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."

Note that, if David Morin is wrong and Tr=Ts, this by no means implies that the frequency of light:

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

does not vary with the gravitational potential. It varies exactly as predicted by Newton's emission theory of light and confirmed by the Pound-Rebka experiment.

Pentcho Valev