Einstein's Lift Experiment: The Principle of Equivalence

[Sandeep T S]

In Principle of equivalence, we indroduce to the theoram by a lift experiment, my question is why the lift is fully closed one, why the observer in lift forbidden to observe out side world

 

[Ibix]

Because the principle of equivalence only applies locally, over a region of spacetime small enough for curvature to be undetectable. Looking out to see if there is a planet there is not a local measurement, and you can easily tell the difference between accelerating in deep space and falling towards a planet if you do that.