If space is flat, the
’s which refer to space remain constant (in a Cartesian mesh-system at least).[100] The only
, or potential, that can vary is therefore the time one
. This last potential is therefore the only one that can be responsible for a field of force. It follows that by considering space to be flat, we are preserving only one of the ten potentials of space-time; and we find ourselves in exactly the same position as under Newton’s law, where only one potential was present, i.e., the Newtonian potential. This allows us to identify the time-potential
with the Newtonian potential
