1. The problem statement, all variables and given/known data 2. Relevant equations L=sqrt(1-(v/c)^2))*l t=T/sqrt(1-(v/c)^2) 3. The attempt at a solution I'm having a hard time approaching this question. could someone tell me how to approach this question. NOT ASKING FOR ANSWER. never mid guys i got it. i forgot to read it happens in the same frame so t=0 correct?
Yup, because the explosions happen simultaneously in Mark's frame and because they occur at equal distances from him. If the explosions were simultaneous in his frame but he was closer to one planet than to the other, the light from one would reach him earlier than the light from the other planet just because it had less travel time to reach him.