Motion, Space, Mass and Causality

Toward a Relational and Causal Interpretation of the Cohesion of the Physical World

General relativity has profoundly renewed our understanding of gravitation by showing that it is not a force in the Newtonian sense, but a manifestation of the structure of spacetime. This intuition of Einstein is correct. However, the geometrization of gravitation, while describing the form of trajectories (geodesics), leaves open a fundamental question: why does a body actually move along such a trajectory?

To say that a body “follows a geodesic” describes a geometrical constraint, not an actual cause. A structure, however coherent, does not act by itself. It is therefore necessary to clearly distinguish the form of motion from its actualization.

Initial and composite motions

Initial motions correspond to the constitution or expansion of the reference space itself. They are not displacements within a pre-existing space, but are foundational of relational space. At this level, there is neither inertia, nor force, nor speed limit.

Composite motions are motions of bodies within this already constituted reference space. It is at this level that inertia, geodesic trajectories, and forces appear when the actualization of motion is impeded.

Gravitation, opposition of tendencies, and appearance of force

In free motion, gravitation does not manifest itself as a force. It corresponds to a non-mechanical relational action integrated into the structure of space. Force appears when this action is impeded.

Proper mass, gravitational mass, and directional mass

Proper mass expresses the intrinsic unity of the body. Gravitational mass is the effect of this unity on the surrounding space.
Directional mass is the oriented actualization of this gravitational structure when motion unfolds; it enables motion, produces length contraction, and reinforces the proper mass.

Inertial mass and impulse

Inertial mass integrates these aspects as the global expression of the body’s relation to space. It results from the integration of the directional reinforcements of proper mass.
Impulse is the dynamic mediation through which these forms of mass are actualized. Force is the expression of an impeded impulse.

The case of the photon and the speed limit

A speed limit is linked to interaction with spatial configuration. It is the reinforcement of proper mass, and thus of inertia, that physically limits motion.
Without proper mass, there is no speed limit, without implying infinite speed. The photon, interacting with space, therefore possesses a relational proper mass, which is a necessary condition for the existence of a speed limit.

Cohesion of the physical world

Each body, through its intrinsic unity, is a mediator of the action of the principle ensuring the cohesion of the physical world.