  A scalar, preferred-frame theory of gravitation is summarized. Space-time is
endowed with both a flat metric and a curved, "physical" metric. Motion is
governed by a natural extension of Newton's second law, which implies geodesic
motion only for a static field. The theory predicts Schwarzschild's exterior
metric in the spherical static situation. It also predicts gravitation waves
with the velocity of light. The equations of motion are recast into the "flat
space - uniform time" form, and compared with the geodesic equations of motion.
The principles of the post-Newtonian approximation of this theory are given,
including the way to account for preferred-frame effects. This approximation is
then developed more particularly for photons. It is found that the
preferred-frame effects do not occur in this case, nor does the difference
between Newton's second law and geodesic assumption. Thus, the post-Newtonian
predictions of this theory for photons are indistinguishable from the standard
post-Newtonian predictions of general relativity.
