The substance of gravity

It is well established that a body of mass will bend a beam of light, but conversely does the beam of light displace the body? Our experimental result obtained with a torsion balance does not confirm the anticipated effect, but the negative result is in line with an elementary estimate that the effect is expected to be beyond our means of detection. Energy density of a power laser beam is minute relative to the universal reference energy density, known as the vacuum, and hence the gravitational force imposed on the body by light is well below the resolving power of our apparatus. We reason that gravity is mediated by photon pairs that embody the vacuum. Therefore, the vacuum exhibits electromagnetic characteristics, namely, permittivity and permeability. However, the physical vacuum embodied by photons is devoid of electromagnetic fields because the distribution of photon phases is even and random. This leaves the space only with the photon-embodied energy density differences which will manifest themselves as gravity. The energy density of free space maintains balance with the total mass of the Universe; and a local energy density, known as the gravitational potential, tends to be in balance with the body of mass. Accordingly, inertia is understood as a least-time reaction taken by the photon-embodied vacuum to restore the universal balance that has been perturbed by the body's change in momentum.