So I was reading that the equivalence principle of Newton doesn't work because of a thought experiment. They said that an experimenter shoots bullets( 1 per second) from the bottom of the elevator to the top. This happens in outerspace where the elevator moves up with accleration g. And this happens on earth as well except there the elevator is stationary realtive to the earth. They said that the in the upwards acclerating case, newtons laws show that the bullets will not strike every second whereas on earth it will. That there is a red shift in the frequency that the bullets hits the ceiling in the accelerating elevator. This doesn't make sense to me. I know that in the accelerating elevator, the top will accelerate away from the constant speed bullets that try to catch up to it. But the same thing happens on earth. It's just that the bullets deccellerate instead of the ceiling moving away. Mathematically both are equivalent. So I'm not sure where the difference comes from. Then it says I dont get how it is "easy to see"