1. The problem statement, all variables and given/known data A spaceship has traveled for 14 years at an average speed of 90% of the speed of light. Its round trip from Earth has taken 14 years according to clocks on the ship. (a) How long has the journey taken according to Earth clocks? 2. Relevant equations t = t’ / (1-v2/c2)-1/2 3. The attempt at a solution I'm totally confused here, I think t' = v * differential of time v = 90% of c c = speed of light But yeah, I need some clarity on what I'm doing here. Any help would be appreciated!