If astronauts could travel at v= 0.950c, we on Earth would sayit takes (4.20/0.950) = 4.42 years to reach Aplha Centauri, 4.29light years away. The astronauts disagree.
a) How much time passes on the astronauts clocks?
b) What is the distance to Alpha Centauri as measured by theastronauts?