Quantum gravity will force us to cut the standard model in half.
In the simplest sense, what we call quantum gravity is the study of how the force of gravity arises from quantum mechanical effects. That might not mean much to most people. The word quantum famously causes a great deal of confusion among not merely the lay community, but also among physicists themselves. Not many people understand what a quantum is, but don’t worry. A ‘quantum’ refers merely to the smallest possible unit of something. A particle in all cases. For instance, the quantum of light is the photon, and a quantum of the electrical force is the electron. But the quantum of the gravitational force is far more mysterious, and has eluded physicists for almost one hundred years. We feel at present that we’re no closer to uncovering the secret of gravity than we were at the beginning of our investigations.
This could come down to the work of Paul Dirac and some; notably, Felix Finster with his causal fermion systems approach to quantum gravity; believe that it could have been that Dirac made a fundamental error in conceptualising gravity that persists to this day. Dirac was given the Nobel Prize in 1933 for his discovery of the positron, a quantum of what we refer to now as antimatter. If Finster’s right about quantum gravity, or close to being right, it means that we have to reimagine gravitational fields as formed of a continuum of negative energy particles in what we refer to as a Dirac Sea. The idea of a Dirac Sea was originally abandoned by Dirac in favour of antimatter. Dirac originally posed the existence of the positron as a hole in the background. If Finster’s correct, it could cause is to have to resurrect this idea of holes in the background and perhaps conceive of W bosons (carriers of the weak nuclear force) to stand in place of positrons. We might therefore be looking at a very different standard model of particle physics; the number of particles in it would decrease by about half; and we’d have to overturn a great deal of twentieth century physics.
In my own investigations into quantum gravity; which share a great deal of parsimony with Finster’s work; I came across the idea of potential gravitoelectroweak interaction. This would be a means of explaining gravity using the electroweak force, the unification between electromagnetism and the weak nuclear force discovered by Weinberg, Glashow and Salam in the 1960s. We might imagine that Finster’s Dirac Sea of negative energy particles are, in fact, electrons tunneling here and there around the universe. The universe would be filled with an enormous number of such particles and they would be readily exchanging photons with one another as well as exchanging other gauge bosons (such as W and Z particles) with other particles of matter. Since electrons are so prevalent in the universe, and since their distribution within objects reflects proportionality to the objects’ mass, it’s not hard to see how; via Newton’s inverse square relation; the electron may well be responsible for gravity. In Newton’s law, gravity is proportional to mass and inversely proportional to the square of the distance between two objects. If an electron could therefore tunnel (no matter how unlikely) to within the electroweak range of a proton in the atomic nuclei of atoms in a foreign object, it could exchange W particles with the atomic nucleus of those atoms leading to a macroscopic force of attraction between two objects.
Think of it this way, all gravitating bodies in the universe would be surrounded at all times by a cloud of tunneling electrons. We cannot see these particles since they’re so small and since they permeate all of space. They would also tunnel to a different location about once every Planck time (about 10^-43 seconds) whenever they interact with another particle. These interactions between particles amount to the exchanges of bosons between electrons and other electrons or other fermions. At each point where the electron absorbs another boson, we say that the wavefunction of the electron collapses, and it tunnels to a new location whereupon it interacts with yet another particle. The cloud of electron surrounding gravitating objects would diminish in inverse proportion to the square of the distance; hence, if you recede from an objects’ surface, you’re less likely to find an electron tunneling from that object. Electrons also make an excellent candidate for a particle of gravity since they absorb and emit photons readily, and we know from Einstein’s theory of general relativity that light interacts readily with gravitational fields, and that gravitational fields are thought to emit photons spontaneously.
This spontaneous emission of photons is what we refer to as the cosmological constant or dark energy, and in our current thinking on the topic we imagine that particles of antimatter are created and annihilate with particles of matter leading, occasionally, to the emission of a photon. I suspect that this is incorrect and that no such thing as antimatter really exists. I suspect that positrons are really tunneling W particles and that this Dirac Sea, or background of tunneling electrons, is really giving rise to this phenomenon of the cosmological constant, or vacuum energy, we observe inn nature. As a consequence, we would need to adumbrate our standard model of particle physics by about half. This ought to be seen as a positive thing in physics. No longer do we have untestable assumptions (such as the creation and annihilation of particles) in our models, and we have a far easier means of now beginning to probe the quantum nature of gravity. The other fascinating consequence of this way of thinking is that gravity would no longer be a fundamental force; instead it would be a secondary effect of electromagnetism. This should have been what we anticipated all along; and now, we might have a quantum theory focusing on only three forces and a theory of gravitation that is truly particle-based.
It could cause a revolution in physics and cosmology and could set us on the path to reappraising all sorts of phenomena in nature. We may gain a better understanding of black hole physics; we may gain the insight that tunneling electrons enter the event horizons of black holes, absorb a particle there, and tunnel out again to deposit it into the background. In this way, we could explain how black holes radiate away. And this process wouldn’t be limited merely to black holes. In line with a recent discovery from Radbound University in the Netherlands, we could anticipate that all objects would radiate away in this manner. We might also seek an explanation for neutrino oscillations (the fact that neutrinos change between their different types or flavours); we could imagine that the background of electrons is exchanging Z particles with these neutrinos and, via a neutral current, the neutrinos change flavour. We could also look to the very early universe and seek an explanation for why there was so much antimatter back then and so little now; a problem known as the baryon asymmetry problem; and rejoin upon our explanation of a universe without antimatter.
It’d be something of a bitter pill for physicists to have to swallow, but it would be a necessary one. If I’ve managed to achieve nothing else in my work on quantum gravity, I think I did at least coin the term gravitoelectroweak interaction, and I might well be the discoverer of that interaction. I’ve been working for many years from the fringes of physics and trying to interest the mainstream with my ideas. As is typical when people do this, I’ve had no luck and haven’t managed to interest any qualified physicists in my ideas. Though I’m not disheartened; I know that the model I’ve produced is testable, that it’s scientific, and that it should stand as a credible means of explaining the force of gravity via quantum mechanical effects. Hopefully, eventually, the scientific community will see the value of it also.
