If astronauts could travel at v = 0.970c, we on Earth would say it takes (4.20/ 0.970) = 4.33years to reach Alpha Centauri, 4.20 light-years away. Theastronauts disagree.
(a) How much time passes on the astronauts' clocks?
(b) What is the distance to Alpha Centauri as measured by the astronauts?