Einstein showed us how an array of unaccelerated synchronized clocks could be set up, extending throughout all space, with a fixed spacing between adjacent clocks. To accomplish that, we only need to assume that the speed of light is exactly the same in all inertial (unaccelerated) reference frames: 186,000 miles per second (which is the fundamental assumption of special relativity). That establishes a meaningful "NOW-at-a-distance", at each instant in that particular inertial reference frame. It allows the question to be asked and answered (by the people stationary in that reference frame): "How old is that particular distant person, RIGHT NOW? That answer MUST be MEANINGFUL to them. If it ISN’T meaningful to them, then the speed of light in that inertial frame can’t be 186,000 miles per second (which is the only thing that the synchronization was based on). So if that answer ISN’T meaningful to them, then special relativity can’t be correct. Assuming that special relativity IS correct (which I certainly believe is the case), the NOW-at-a-distance given by the array of unaccelerated clocks MUST be considered to be meaningful by the people stationary in that inertial reference frame.But how about an array of clocks, with a fixed spacing between adjacent clocks, which are all equally ACCELERATED? Can they establish a meaningful NOW-at-a-distance for a person who is stationary with respect to that array of accelerating clocks (and co-located with one of them)? The answer is YES! Those clocks can’t be synchronized: they run at different rates. But if they are synchronized at the instant that they all start the acceleration, then a person (he), stationary with one of the clocks, can CALCULATE the current time on each of the other clocks, at each instant of his life during the acceleration. THAT effectively establishes a NOW- at-a-distance for him: it allows him to determine the current age of any particular distant person (her), according to him. And he MUST consider that answer to be fully MEANINGFUL to himself.