Quantum nonlocality is the ability of one photon when measured to instantly determine the state (spin up, spin down) of its conjoined twin at an arbitrary distance.
If you are familiar with entanglement and quantum nonlocality, continue; if not go here.
The instantaneous aspect of quantum nonlocality appears to violate the speed limit of light as postulated by special relativity. Nonlocality is also said to render scientific realism untenable. Photons exhibiting quantum nonlocality (entanglement) are said to be "conjoined."
If there is a reasonable/realist/non-spooky explanation for nonlocality – as Einstein would have insisted there must be – then we must expect the presence of something physical (mass or energy) that binds conjoined photons together despite their (apparent) space separation. We first need to take a close look at the ontology (existence, occurrence) of particles, projectiles and photons beginning with some definitions.
When energy is stored it is potential and when it is not stored it is kinetic. Hence free energy (radiation) is kinetic and stored energy (in the atom, in a watch spring) is potential. Applying the same terminology, ordinary mass (rest mass) is kinetic and mass that depends upon energy (relativistic mass) is stored and therefore is potential.
A projectile combines both kinetic (rest) mass and kinetic energy but what happens when we subtract one of those components from projectile motion? If you have kinetic energy of motion but no kinetic mass then you have the photon; if you subtract the kinetic energy from a projectile then you have an inertial/at-rest mass. According to special relativity the photon is stationary in time and the inertial mass is stationary in space; both are known as "pure" entities in ontology since they feature kinetic mass or kinetic energy, but not both.
Pure entities obviously have a kinetic identity, but they also have a potential identity. This means that pure entities will store their opposite number: unchanging inertial mass stores potential energy while the photon stores potential (relativistic) mass. Whatever a pure entity stores constitutes that entity's potential identity and it is this identity that progresses in the dimension in which the entity is not stationary. Thus the potential (energy) identity of an inertial mass is stationary in space but progresses over time towards its ultimate release. And the potential (mass) identity of a photon is stationary in time but progresses over space towards its ultimate release. Projectiles progress over both dimensions; the potential identities of pure entities progress over only one dimension. Since a photon is bereft of rest mass and it is stationary in time it cannot be a projectile and it cannot have a trajectory; only its stored identity progresses in space.
Potential energy as stored by a massy particle exists and extends over space hence it has the field form. Potential mass stored by the photon has been recognized quantitatively (as relativistic mass) but it has been denied a form. This is a serious oversight.
Photon kinetic energy is oscillatory and so is the mass which it stores. As a consequence, oscillation plus space progression makes photon potential mass a wave and this permits interference effects and creates a probability distribution over space of possible photon termination points. Just as field is the form of an atom's potential energy, so wave is the form of the photon's potential mass
A photon's potential mass is immaterial (no rest mass) and it occurs rather than exists. Hence the space progression of wavy occurring potential mass does not burden photon space paths with anything substantive. Photon potential mass can spread and rarefy indefinitely in space as an occurring wave and yet be annihilated instantaneously because it is an occurrence unencumbered by rest mass: it is a unitary, latent, space-progressing pure occurrence.
Just as space-adjacent atoms will share existing potential energy over time and be conjoined, so time-adjacent photons will share occurring potential mass over space and be conjoined. Two conjoined photons do not fly off projectile-like in different directions as separate particles (photons are not particles and they do not have trajectories!). Instead conjoined photons remain temporally linked as occurrences and it is their shared potential mass as occurrence that progresses over all available space paths. At some point the potential mass of one photon terminates (releases upon a material target) and this will instantaneously affect its unterminated partner.
The concept of photon potential mass does provide a rational and a physical explanation for quantum nonlocality. It also has the heuristic advantage of reestablishing the fundamental symmetry of mass and energy: existing mass quanta storing and then releasing energy over time versus occurring energy quanta storing and then releasing mass over space. But this concept goes beyond that.
I Potential mass as a wave explains the probabilistic nature of photons: termination on a target is individually random but collectively deterministic.
II Potential mass explains the basis of wave-particle duality. Photon potential mass progresses in space as a wave and exhibits all the usual attributes of wave behavior (dispersion, attenuation, interference) and yet when photon stored mass is released it becomes kinetic and space discrete mimicking the arrival of a particle.
III The space progression of potential mass explains why any attempt to determine which path a photon followed ("which-way" experiments) is doomed to failure. Potential mass follows all paths.
IV Potential mass explains the supposed "interaction-free measurement" of the puzzling Elitzur-Vaidman thought experiment.
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Physicists have misinterpreted the nature of the photon ever since it was first proposed and then verified in the early 1900s. Physicists at the time were wedded to classical physics and mechanistic (matter-based) explanations. Radiation, quantized or not, had to be either ripples hosted by a material medium (the aether) or tiny (material) particles expelled from a luminous source and following a trajectory. Once the aether was discarded the classical particle/projectile concept remained and radiation quanta were given the particle-like name of photon. But photon wave behavior wouldn't go away and so the photon became a contradiction: both a particle and a wave.
The best minds of the 1920s and later were unable to explain the puzzles which the photon presented: duality, nonlocality, probability and interaction-free measurement. The fault, many of them agreed, lay with the very nature of reality: a reality that was both inaccessible and inexplicable in terms of human inquiry. Actually the fault was much less grand than that. It was the failure to recognize that "relativistic" mass – so new to physicists at the time – was really potential mass which possessed a form and had a dimensional presence and progression just as potential energy possessed a form and had a dimensional presence and progression.
The preceding leaves out supporting arguments and extensions of these ideas. These may be found in the book.