Question

Imagine that you are sitting in a closed room (no windows, no doors) when, magically, it is lifted from Earth and sent accelerating through space with an acceleration of 1g (9.8 m/s2). According to Einstein's equivalence principle, which of the following is true?
You won't feel any change and will have no way to know that you've left the earth.
You'll feel a force that will cause your head to repeatedly bang into the ceiling.
You'll know that you left the Earth because you'll be floating weightlessly in your room.
You'll know that you left the Earth because when you drop a ball it will fall sideways.

Answer 1

Answer:

You won't feel any change and will have no way to know that you've left the earth.

Explanation:

One of the formulations of the principle says that the properties of an inertial system under the effect of a gravitational field are the same as a non-inertial(accelerated) system. The inertial system under the effect of a gravitational field occurs when you are in the room on earth, and when the room is sent accelerating through space you have the non-inertial system. Both have the same properties, so it's impossible to tell the difference if you can't look outside.