The → equivalence principle as stated by Einstein, on which is
based the theory of → general relativity. It comprises
the three following items:
1) The → weak equivalence principle is valid.
2) The outcome of any local non-gravitational experiment is
independent of the velocity of the freely-falling
→ reference frame in
which it is performed. Also known as → local Lorentz invariance.
3) The outcome of any local non-gravitational experiment is
independent of where and when in the Universe it is performed. Also called
→ local position invariance.

A fundamental concept of physics, put forward by A. Einstein, that states that gravitational and
inertial forces are of a similar nature and
indistinguishable. In other words, acceleration due to gravity is equivalent to acceleration
due to other forces, and gravitational mass is the same as inertial mass.
Same as the → principle of equivalence.