Space deals with relationships; and time deals with the history of those relationships.
An inconsistency may be spotted in space, but to resolve it we need to go into the dimension of time.
Static relationships are determined by relative positions and directions in space. Dynamic relationships have the additional dimension of time.
In geometrical space, positions are represented by points, and directions by solid angles. A solid angle further resolves into two planar angles in two different dimensions.
In physical space, positions are represented by objects, and the directions by relative positions. If there are no objects, the positions are determined by mental imagery.
An object is defined by its inertia expressed as mass. Inertia is a measure of how much structure is there. The structure appears by its resistance to change.
An object cruising at constant velocity cannot be differentiated from an object at rest. There is zero acceleration. Therefore, its actual motion is also zero.
Motion arises only with acceleration, as when force is applied, or during interactions among objects.
The reference point for an object shall be zero inertia and zero acceleration.
When inertia is zero then there is no resistance to work against, and no acceleration is possible. An object with zero rest mass shall always remain in a state of zero acceleration or constant velocity. This is the case with light.
An object with non-zero rest mass has non-zero inertia, and it can be accelerated by applying force to it.
When there is an object with mass M1 in space all by itself, and there is no second mass and no distance either, then the force due to gravity would be undefined.
The moment an object of mass M2 appears in space, the distance d between the two objects also gets defined, and a force and acceleration also appear.
