1. The problem statement, all variables and given/known data A spaceship departs from Earth for the star Alpha Centauri whic is 4 light years away. The spaceship travels at .75c. Howlong does it take to get there (a) as measured on Earth and (b) as measured by by a passenger on the spaceship 2. Relevant equations proper time = delta(t')=2D/v delta(t)=delta(t')/sqrt(1-v^2/c^2) 3. The attempt at a solution In part a, the observer is going to the measured that the earth travels at the speed of light, so I would used the equation , delta=delta(t')/sqrt(1-v^2/c^2) In part b, the observer on the space ship is going to measured the proper time and will not notice that the spaceship is traveling closed to the speed of light . so he will used the equation delta(t') =2D/v= 2*(4*light*years)/(.75c) Are both my observations correct?