Suppose there is a rocket that is traveling at a constant .9c starting at an initial position x1 and fires a photon every second to observers on earth. (Observers on earth do not know the velocity of the rocket) If 1s is the proper time [itex]\Delta[/itex][itex]\tau[/itex] then the time passed on earth between each photon being fired would be [itex]\gamma[/itex] or 2.29416s. Then dependent on the initial position x1 the time between each measured photon on earth would be the time for each photon to travel the distance d from each position x at every 2.29416s? From measuring the time between each photon that reaches earth you could calculate the positions x2...xn. But you would only be able to know the positions of where the rocket was not where it is presently. Assuming I understand the above, how would someone go about by calculating the positions if the rocket is accelerating?