The origins of the equivalence principle begin with Galileo demonstrating in the late 16th century that all objects are accelerated towards the center of the Earth at the same rate. This was codified by Newton with his gravitational theory in which it was postulated that inertial and gravitational masses are one and the same.
The equivalence principle proper was introduced by Albert Einstein in 1907. At that time, he made the observation that the acceleration of bodies towards the center of the Earth with acceleration 1g (g< ...
A number of different forms of the equivalence principle are used in research today.
Equivalence principle - The weak equivalence principle.
The weak equivalence principle, also known as the universality of free fall:
The trajectory of a falling test body depends only on its initial position and velocity, and is independent of its composition.
or
All bodies at the same spacetime point in a given gravitationa ...
