Physlet Illustration: Principle of Equivalence

 

 
Rocket's frame of reference Stationary frame of reference
In this simulation, a rocket accelerates upward. As it moves upward, something  is shot in through a window on the side of the rocket. You may observe the simulation either from a stationary reference frame, or from a frame that accelerates along with the moving rocket. How does this demonstrate the Principle of Equivalence?

Hints

  1. In the stationary reference frame, what sort of path does the object follow?
  2. In the rocket's reference frame, what sort of path does the object follow? (Does the shape of the path look familiar?)
  3. Suppose that the object is a ball, thrown horizontally in outer space where gravity is negligible. To an experimenter inside the rocket, what could account for the path of the ball? Would the experimenter conclude that there is gravity  present?
  4. Suppose that the object is a photon, fired horizontally by a person outside the rocket. To the experimenter inside the rocket, what could account for the path of the photon? Is light affected by gravity?

Reference

See Walker, Section 29-8

Illustration written by Mario Belloni and Steve Mellema