If astronauts could travel at v = 0.990c, we on Earth would say it takes(4.20 / 0.990) = 4.24 years to reach Alpha Centauri, 4.20 light-years away. The astronauts disagree.
(a) Find how much time passes on the astronauts clocks?
years
(b) Find the distance to Alpha Centauri as measured by the astronauts?
light-years