1. The problem statement, all variables and given/known data Two planets A and B have relative velocities 0.7c. They can observe the birth of two stars, C and D. According to planet A, star D was born 10 years before star C was born. According to planet B, star C was born 20 lightyears farther than star D. What is the time difference between the birth of the stars in the reference frame of planet B. The attempt at a solution S: Planet A S': Planet B β=0.7 → γ=1.4 Δt'=γ(Δt-βΔx) Δt'=-5.6 I assume this is incorrect. I am really struggling with relativity, and my textbook only has a short section which doesn't explain too much. Any help will be appreciated.