Historical research guide · 1060 · 2018
On the carrier of inertia
Patrick Grahn · Arto Annila · Erkki Kolehmainen
In one minute
Patrick Grahn, Arto Annila and Erkki Kolehmainen ask the question textbooks skip: when you push something and it pushes back, what exactly is doing the pushing? Their answer is that the vacuum is neither empty nor abstract — it is made of photons travelling in pairs exactly out of phase, so their electric and magnetic fields cancel. A pair carries energy but shows no field, which is why space looks dark and inert. Shift the phase, near a charge, and the fields appear at once: that is electromagnetism. Leave the photons paired and their coupling to matter is what we feel as gravity and as inertia. Because the pairs are everywhere, the reaction to a push arrives instantly even though photons travel at the speed of light. The authors then walk the picture through the Hong-Ou-Mandel experiment, the equivalence principle, the Casimir and dynamical Casimir effects, the double slit, Aharonov-Bohm and the Tajmar effect — looking, as they say plainly, for the observation that would falsify it.
Connection
Chapter 3 argues that inertia and gravity are the vacuum’s reaction rather than properties matter simply has; this paper gives that reaction a named carrier, and in doing so hands chapter 2 a concrete answer to what the vacuum is made of. It also connects straight to chapter 10, since it reads the Lorenz gauge as the physical equation of motion of that medium and the Aharonov-Bohm phase shift as a measurement of its density.
From the source
The proposal in one line: photons in free space do not travel only as single quanta but in pairs, the two exactly out of phase, so their electromagnetic fields sum to zero. A pair then carries energy density with no net field — which is why space is dark and inert. Shift the phase away from complete destructive interference, as happens near a charge, and the fields appear immediately. The authors read the Hong-Ou-Mandel experiment of 1987 as the demonstration: two identical photons meeting at a beam splitter pair up for co-propagation, because a pair with no net field is lower in energy than two distinct photons, and no light is seen.Section II, The photon-embodied physical vacuum, and figures 1 and 2
The energy books balance. The vacuum as the universal gravitational potential and the total mass of the Universe satisfy the zero-energy principle — the total mass times the speed of light squared, minus the gravitational constant times the squared total mass divided by the radius, is zero. Written as a unitary condition this reads: the gravitational constant times the mass divided by the speed of light squared times the radius equals four pi times the gravitational constant times the average density times the squared age, and that equals one. With the Universe’s radius the speed of light times an age of 13.8 billion years, an average matter density of 6.12 times ten to the minus twenty-seventh kilograms per cubic metre corresponds to an average energy density of 0.55 nanojoules per cubic metre. The authors draw the consequence that in an evolving Universe the speed of light and the gravitational constant cannot be constants but functions of the decreasing universal energy density.Section II, paragraphs on the zero-energy principle and the unitary condition
Inertia can look instantaneous and still be radiative, because the medium is already everywhere. There is no dilemma with an instantaneous reaction despite the finite speed of light, provided the paired-photon energy density is at hand at every point: the omnipresent substance reacts to any action at once. Only a massive dematerialisation far away — out at a distant galaxy — would perturb inertia here, and that perturbation would arrive at the speed of light and could in principle be detected as a reaction force on a body rather than only by interferometry.Section III A, Radiative and instantaneous inertia
Mass becomes a coupling constant rather than a possession. Since both the universal vacuum and a local gravitational potential embody the same paired photons, the equivalence of local and universal coupling is inescapable and the equality of gravitational and inertial mass stops needing a separate explanation. The authors point to the sharpness with which mass can change — a W boson decaying to an electron and an antineutrino takes 80 gigaelectronvolts of mass to 0.511 megaelectronvolts — and to electrons in graphene behaving as though their mass were peculiar while the electrons themselves are ordinary and only the surrounding field is unusual.Section III C, The equivalence principle
Gravity is then a force after all, driven by density differences in the medium. Bodies move toward each other when quanta in the dense field between them escape to sparser surroundings — that is why an apple falls — and apart when quanta stream in from the surroundings, which is how the authors read cosmic expansion. Gravity in this picture is not exclusively attractive, and it is dissipative, which makes it falsifiable: where initial and final states differ there ought to be a sign of dissipation, and the authors point to the anomalous acceleration spacecraft acquire during planetary flybys as one such sign. The universal energy-density gradient gives an acceleration of the order of the speed of light divided by the age of the Universe, about ten to the minus tenth metres per second squared.Section III D, Gravity as an energy difference
Two ways to break it, offered by the authors themselves. First, the gravitational wave: on this account it is not a temporal distortion of an abstract metric but a tangible density wave, so its passage should amount to an increased index along the optical path of a diffractometer rather than a modulation of an interferometer arm’s length. Second, the Tajmar effect: a superconducting ring is read as accepting surrounding quanta only in pairs, so the phase-locked quanta follow the ring when it is set rotating, and the authors state the sharp prediction that the phase-locked region of space ought to map the magnetic-field-excluded region. They are candid about the limit of the model — asked how to calculate inertia from the proposed structure of the vacuum, they answer that this is not possible, because the structure of the particle would have to be known as well.Sections III H and IV A, and the closing paragraphs of section IV D
The way in
https://doi.org/10.1063/1.5020240How to cite it
Patrick Grahn, Arto Annila, Erkki Kolehmainen (2018) On the carrier of inertia doi:10.1063/1.5020240