It's the stumbling block that everyone has grasping this stuff, and it's rooted in the old faulty kind of speed calculations. Speeds don't add like you think.

It's the stumbling block that everyone has grasping this stuff, and it's rooted in the old faulty kind of speed calculations. Speeds don't add like you think. There are many ways to grasp this, and one has to try several of them to find an intuitive explanation that works for onesself; but one way is to consider that you, in your spaceship (as long as you are coasting along with no rockets firing, and aren't performing orbit/deorbit burns) are, in your frame of reference, at rest. Your speed is zero. You haven't approached anything at all, and light is still whizzing away from you at c. Indeed, it's Terra and Luna that are experiencing time dilation as far as you are concerned, because they are the ones with the high speeds. * https://www.youtube.com/watch?v=Zkv8sW6y3sY https://www.youtube.com/watch?v=Zkv8sW6y3sY (FloatHeadPhysics addressing this in another way: there are a other approaches still) Accelerate at the beginning and end of your trip over to Luna, and of course general relativity comes into play and things get more complicated. What many gedankenexperiments get wrong is that usually there's only a short period of burning the rockets, in the real world. So for most of your trip in the rocket you aren't burning propellant and are in an inertial frame of reference. No inertial frame of reference approaches the speed of light/causality, by postulate 2 of special relativity, and one is always at speed zero in one's own inertial frame of reference.