1. The problem statement, all variables and given/known data E.g.: A spaceship flies past Mars with a speed of 0.985c relative to the surface of the planet. When the spaceship is directly overhead, a signal light on the Martian surface blinks on and then off. An observer on Mars measures that the signal light was on for 80.0ms. I have to find out, how long time passes when measuring the pulse of light by the pilot of the spaceship? 3. The attempt at a solution From the observer on Mars, it takes 80 ms. From the pilots inertial frame, it must take a longer time, because of the Lorentz factor. But how does this add up with the fact, that the pilot wont have aged as much as the observer on Mars when the flight has ended? Because with my calculations, something about ~460 ms is the duration of the pulse. But that is longer time, which is good because of the Lorentz factor, but he will have aged more then? Or is 80 ms to the pilot, and ~460 ms to the observer on Mars?