At what speed would an astronaut need to travel so that he would age 4.20 years while traveling a distance (as measured by an Earth observer) of 4.20 ly?
A) 1.00 c
B) This cannot be done.
C) 0.50 c
D) 0.707 c
E) 0.750 c

Question

Quizplus · Accepted Answer

Using the formula for time dilation, we have t' = t/sqrt(1-v^2/c^2), where t is the time as measured by the Earth observer (4.20 years), t' is the time experienced by the astronaut, v is the velocity of the astronaut, and c is the speed of light. Solving for v, we get v = sqrt(1 - (t'/t)^2) * c. Substituting the values given, we get v = 0.707 c. Therefore, the answer is D.

At What Speed Would an Astronaut Need to Travel So