Alice travels from earth to a planet 10 light-years away from earth, travelling at a constant 0.8c. how long does the trip seem to take, from alice's perspective? work this problem two ways: a) first do it from earth's perspective, and use the time dilation equation to figure out what alice's clocks are reading. b) then do the whole problem from alice's perspective; if you're not getting the same answer, you're forgetting a crucial piece of relativistic physics.