A friend of mine, Amir Assarzadeh, upon noticing my thought experiments [1&2], asked me an intriguing question to which he also made an answer defending Einstein's equivalence principle (EEP). However, I thought that it is worth discussing here:
Assume a very massive planet and a shuttle at rest WRT the planet though keeping a large distance from it so that the effect of the planet's gravitational field is negligible on the shuttle. If we locate two similar clocks, one in the shuttle and the other on the surface of the planet, there would be a discrepancy between the clock rates for the very moment at which the shuttle starts up its engines undergoing a similar acceleration to the planet's gravitation from the viewpoint of the Schwarzschild observer.
In other words, we all know that the clock on the massive planet runs slower due to the gravitational time dilation as measured by a Schwarzschild observer, however, as the shuttle starts up its engines, the clock does not change its rate because the shuttle has still a zero relative velocity WRT both the planet and the Schwarzschild observer. Although the observer in the shuttle claims that EEP is held true at the moment of and all during the firing of the engines, and thus he anticipates that his clock must run slower similar to that located on the planet, the Schwarzchild observer claims that there is no time dilation for the shuttle's clock because it has no considerable velocity compared to that of light. Is this a paradox?
My friend, however, made a simple answer to this anomaly as to which I am not convinced. He claimed that EEP is applicable only for the observers inside the shuttle and on the planet. That is, a Schwarzschild observer is necessarily not able to use EEP for other noninertial observers from his own viewpoint.
Do you think his answer is valid?