On the Pioneer acceleration as light acceleration
As early as in 1907, Einstein showed that the light speed must be larger at spacetime points with higher gravitational potential. This idea is used here to present a relativistic version of a recent model which explains the acceleration of the Pioneer 10 spaceship as the effect of a universal adiabatic acceleration of light. This phenomenon would have the same observational signature as an acceleration of the ship. It is shown in this work that such acceleration would be due to an acceleration of the proper time with respect to the coordinate time. PACS numbers: 04.80.Cc, 95.10.Eg, 95.55.Pe