An observer outside the rocket sees a light beam through a rocket that's accelerating. How will an observer inside the rocket see the light beam? (The problem is showed in the picture below) My friends and I had this problem at school today, and we couldn't decide which is right. Here are our thoughts: 1) The rocket has a speed relative to the observer outside. 2) The person inside will experience a acceleration, which is equivalence to gravity. After reading the books and seen some pictures, I think the right answer is that the light beam will bend. I hope someone can explain it in details. I don't understand why the observer outside don't see a bend light beam because the rocket has a speed and acceleration. Thanks for the help!