Faraday was the first recorded person who truly believed that spacetime is not empty but he lacked mathematical knowledge to describe it fully except as fields or lines-of-forces. Now it can be hypothesized not only spacetime is full, this fullness can also resist the linear flow of anything whether matter or energy. Note also that rotational flow of spacetime exists. If this resistance is exactly zero then the quantum spacetime is truly rotational and it can be called the true vacuum. Its linear speed is infinite. However, for the false vacuum the speed of its linear resistance is approximately 300 millions meters per second, also known as lightspeed.

In the science and technology of electrical engineering it has already been determined that the linear speed of electron flow known as the uniform drift velocity within conductors is only about a million meters per second (a third of a percent of lightspeed). Fortunately within these tiny variations in the immediate neighborhood of this uniform drift velocity, all the devices and machineries of modern technologies (e.g. electric motor, telegraph, telephone, radio, TV, and all electrical appliances) are made possible. Extending its applicability would be tiny variations in the subluminal neighborhood or tiny variations in the superluminal neighborhood. Incidentally, applications in the immediate subluminal neighborhood have already been accomplished in most particle accelerators (e.g. LHC of CERN). However, most are based in rotational flow with some exceptions (e.g. SLAC, Stanford’s linear accelerator). The resistance of matter is known as inertia. Although inertial mass and gravitational mass are derived from different physical concepts, they are practically equivalent as experimentally shown using pendulum of varying length by Newton in the 17th century, verified more accurately by Bessel in the 19th century, later by Eötvös using torsion balance, then Dicke, et al, at Princeton improving Eötvös method arrived at the same conclusion: the principle of equivalence between inertial mass and gravitational mass.

But in 1905 Einstein already showed that the relative vacuum resistance between energy (E) and mass (m) is given by E=mc˛ (c is lightspeed). Now it can be shown that the relative resistance between the false vacuum (S) and energy (E) is S=cE. Therefore by direct substitution the relative resistance between S and m is S=mcł. In a theory of quantum spacetime, S is called continuous spacetime while quantum spacetime (H) is known as square of energy (E˛) as the true vacuum of exactly zero linear resistance. Consequently, the total linear momentum (P) of the universe could be defined as the ratio of H and S: P=H/S. Substituting E˛ for H and cE for S gives the correct linear momentum of light: p=E/c, its energy content divided by its speed.