Question

Suppose you decide to travel to a star 65 light-years away with a speed that tells you the distance is only 25 light-years. How many years would it take to make the trip?

Answer 1

$t=t_0\sqrt{1-\frac{v^2}{c^2}},$

$v=c\sqrt{1-\frac{t^2}{t_0^2}}=0.923c,$

$T=\frac sv=70.4$ years.