The Equivalence Principle

Enunciate the Equivalence Principle in various ways.

1. It is not possible, in a LOCAL experiment, to determine whether a laboratory is suspended in the gravitational field of a large body causing a gravitational acceleration \(g\) or whether it is gravitationally free and being subjected to a constant acceleration \(g\).

2. There are no LOCAL experiments that can distinguish whether a laboratory is free falling in a gravitational field or whether it is resisting UNaccelerated in gravity-free space.

3. In a homogeneous gravitational field all operations run exactly the same way as in a uniformly accelerated, but GRAVITY-FREE reference frame.

4. A laboratory in a gravitational field, falling freely and NOT rotating, is an INERTIAL FRAME in the sense of the Special Theory of Relativity.

5. The effect of gravity can be locally produced or reversed by a suitable acceleration.

Reference:
Epstein Explains Einstein
An Introduction to both the Special and the General Theory of Relativity
“As simple as possible - but not simpler !”
by David Eckstein
Image: http://www.descsite.nl/Gravity_us.htm