1. The problem statement, all variables and given/known data According to observations on Earth, the distance to nearest star is 4.5 light-years. A ship which leaves earth takes 4.25 years (according to onboard clock) 4.25 years to reach this star. Calculate the speed at which this ship travels. 2. Relevant equations (I think) x' = [tex]\gamma[/tex](x-ut) t' = [tex]\gamma[/tex](t-ux/c2) L = L0/[tex]\gamma[/tex] 3. The attempt at a solution so we know: x = 4.25 light years, and, t' = 4.25 years. using length contraction, L (or x') = 4.25 / [tex]\gamma[/tex]] So i tried using this in x = [tex]\gamma[/tex](x' + ut') but only managed to get 0 = [tex]\gamma[/tex]ut'. I can't find any other way of reducing variables to obtaining new variables and would love a push in the right direction. Thanks in advance.