The Andromeda glaxaxy is two million light-years from earth, measured in the common rest frame of the earth and Andromeda. Suppose you took a fast spaceship to Andromeda, so it got you there in 50 years measured on the ship. If you sent a radio message home as soon as you reached Andromeda, how long after you left earth would it arrive, according to timekeepers on earth? Note that radio waves travel at the speed of light. _____ How do I go about this question? With my own calculations I got a negative imaginary number. What I did was I found out the speed of the spaceship, and I got it to be 40000c. I'm not sure if this is right. Any help would be greatly appreciated.