Einstein’s “Happiest Idea” - I
Consider a rocket ship far in space (gravitational forces are negligible).
An astronaut releases 2 balls (of different mass) when the engines are on and the rocket has constant acceleration.
- From point of view of observer that is not accelerating (inertial reference frame): The rocket and astronaut continue accelerating but the balls do not accelerate. The balls do not “keep up” with the rocket, so the bottom of rocket “catches up” to meet the balls
- Rocket “catches up” to both of the balls at the same time, since each one continues to move at same velocity (law of inertia).