Between two scalar potentials, interferometry is:
- Interference of the multi-wave sets in hyperspace.
- Production of gradients in the 3-space point values
- In the classical (erroneous) postulation, the creation of forces in 3-space.
    > Force does not exist until the gradient couples to an
        observable mass.
    > There are no E-fields and B-fields as such in the
        massless vacuum, but only potential gradients.