The ill-formed part of your question is the "in one second" part. From the point of view of the observer on the spaceship, the photon will be ~300k km away afte

The ill-formed part of your question is the "in one second" part. From the point of view of the observer on the spaceship, the photon will be ~300k km away after one second. From the point of view of an 'stationary' observer, the photon will be (one second * (c - spaceship_speed)) away from the spaceship. How can this be? Answer, as the grandparent said: time is passing differently for the person on the spaceship than it is for the person outside. It is passing in such a way that, for each of them, the speed of light is exactly c. (edit: corrected 300km to 300k km)