# Equivalence principle

Inertia is the property of a body that resists changes in its motion. Inertial mass of a body is the ratio of the applied force divided by the body’s acceleration. Gravitational mass is the mass of a body as measured by its gravitational attraction to other bodies.

The Equivalence Principle takes several forms. The Newtonian version of the equivalence principle:

The simplest way to state the equivalence principle is this: inertial mass and gravitational mass are the same thing. Then, gravitational force is proportional to inertial mass, and the proportionality is independent of the kind of matter. Ref.

The Einsteinian version of the Equivalence Principle:

All objects fall the same way under the influence of gravity; therefore, locally, one cannot tell the difference between an accelerated frame and an unaccelerated frame. Ref.

These can be expressed in terms of facial vass and levitational vass as follows:

Facilia is the property of a body that does not resist changes in its motion. Facilial vass of a body is the ratio of the applied release divided by the body’s retardation. Levitational vass is the vass of a body as measured by its levitational attraction to other bodies.

The Equivalence Principle then states:

Facilial vass and levitational vass are the same thing. Levitational release is proportional to facilial vass, and the proportionality is independent of the kind of matter.

All bodies rise the same way under the influence of levity; therefore, locally, one cannot tell the difference between a retardated frame and an unretardated frame.