With admittedly little insight into the mathematical operations that underscore current interpretations of classical and quantum physical laws, this writer (having read numerous books on the subject) has yet ended up confused more than informed. Part of the reason has to do with the writing style of author-physicists who, admirably, seek to popularize complex topics. While some stick to concrete ideas and definitions others lapse into abstractions with no spatial, geometric or experiential foundation, i.e. concepts that don't seem to coincide with the world we live in; for example multi-verses, time travel and the existence of extra dimensions. Often unable to bring their explanation down to earth, they rely on cart-before-the horse mathematical models to create reverse resolution.
While this method is reasonable the speculation typically goes well beyond that into areas that might never be confirmed or refuted. At times it seems in their zeal to uncover a theory of everything, these thinkers come up with so many "every-things" as to be left with nothing. In this opinion, science should dovetail at least loosely with common sense. In that context, a series of items is discussed in concrete terms about current theory and the nature of our world.
The confusion-driven search for a theory of quantum gravity is feverish in scientific circles. Confusion results from the fact that on a large scale gravity is lawful with regard to the influence of one body on another (whereby the more massive body will draw the less massive one in via an inverse square law based on the respective mass and distance between the two). However this only applies to objects with mass equal to or beyond that of an atom. The subatomic (quantum) world acts differently, particularly regarding massless particles which move around seemingly on their own, independent of surrounding matter and in a way that makes it impossible to track their position and momentum sequentially.
At face value this conflict begs for resolution which is why physicists have sought a theory of gravity that encompasses both General Relativity and particle (quantum) physics. But is this confusion justified?
Do we need a theory of quantum gravity?
One could ask: if gravity is a function of mass and particles such as photons and electrons have no mass, why they should behave as if in a gravitational relationship? How can something that "weighs" nothing attract something else? In addition, "mass" reflects the congestion of particles or atoms within a body; for example uranium, with an high density of atoms has greater mass than a more sparsely congested liquid such as water. As the density of a body decreases (at some point down to a single particle such as a quark) it would have less mass. With only one particle there can be no congestion unless the particle itself has internal components that congeal. Even then, (assuming there exists a root form of matter which cannot be further broken down) there would have to be a point where gravity could not pertain due to zero mass. In other words, gravity is ultimately a spatial, mathematical composite that cannot exist without at least two components pressing on one another. As an aside, this is something to consider when discussing the mass of any singularity. More specifically, once anything is whittled down to a single body can its information/communicative content reach a point where its implicit redundancy adds up to zero congestion and zero mass, despite the antecedent "crunching" of diverse elements that ended up in a singularity?
In that context one could argue that Einstein's model of gravity is sufficient; the search for a quantum/classical combine unnecessary.
Beyond that, since both gravity and massless particles travel at light speed wouldn't gravitational influence on the particle be canceled out as a result of relativity? For example if you travel at 100 mph on a highway and a wind of 100 mph is facing you, your car would come to a stop - all things being equal, and exhibit neither momentum or regression. Along the same lines; gravity would require differentials in mass, acceleration etc. (something that is discussed below in term of Information Theory).
Furthermore, celestial bodies do not simply adhere to gravitational relationships. All are hurtling through space at enormous speeds. As a result it isn't just gravity that is influencing their movements, but also momentum, centripetal and centrifugal force, inertia or "drafting" (as when a cyclist cuts down on friction by undercutting wind factors when riding directly behind a competitor) and the action/reaction principle as depicted in Newton's third law of motion - the latter holds that as a body thrusts forward it does so into an atmosphere containing some matter (not all of space is a vacuum), which leads to a counter-reaction in the opposite direction. Conceivably any and all of these forces are influencing planetary and galactic movement. Is it possible that the acceleration of the universe, as well as dark matter could be explained as some juxtaposition of all these influences rather than through a single explanation such as superstring theory, brane theory or hologram theory?
One interesting thought experiment would be to imagine gravity's influence if all bodies, notwithstanding mass and distance, were completely inert: that is, had no momentum, rotation, or any susceptibility to centripetal, centrifugal forces, drafting, or action-reaction mechanics. Presumably gravity could not exist in such a state because in an inert universe any sort of gravity-induced attraction/collapse would entail a change in momentum, i.e. movement. Thus, if lack of motion cancels out gravitation then one might assume motion is the most essential correlate, or even cause of gravity.
At face value the notion that particles have no lawfully discernible locations or momenta and can act lawfully only when observed seems either weird or tautological, depending on one's perspective. One explanation for this phenomenon (the anthropic principle) holds that the observer is implicitly connected to the physical world, thus can never truly be an observer. In other words he is as dependent a variable as the particle being observed; it is as if only God can truly be an observer. Other explanations refer to the particle being virtual, darting in and out of reality or parallel universes, thus being beyond the circumscribed physical laws peculiar to our universe. Both explanations raise the question of why, even if the observer changes the particle's behavior, both wouldn't be subject to physical laws.
This point has been made far more eloquently. For example Witten believed the act of observing stimulated particles because the observer's vision could only occur by firing photons at the particles (Zimmerman-Jones, Robbins 2014) - leaving the observer in roughly the same position as someone bobbing for apples. Others, for example Bohr, argued against this idea, stating that the uncertain nature of particle behavior is built into the particle and nature itself; seemingly mysterious, then again, perhaps not.
Mind and Matter...
One way to address this issue is by discussing the layout of the human brain. Early Russian research, beginning with Pavlov, demonstrated the existence of a brain mechanism known as the second signal system. He demonstrated that the dual hemispheric makeup of the cerebral cortex leads us to categorize experience in two ways: one spatial/material and one associative i.e. symbolic/linguistic (Windholz 1990). The encoding of the former onto the latter - much like a card catalogue - enhances not only our communicative capacities but also our memory storage. For instance we don't have to commit to visual memory all items in the sequence... 'apple', 'orange', 'pear', etc. because we can assign the label "fruit" to each and access all of them by cross reference. As a trite, but perhaps amusing aside it appears that by conceptual symbolic thought our brains are able to override the quantum (individual, piece by piece) model of nature favored by quantum physicists through nifty, integrative mental mechanisms.
Yet while this neural mechanism provides a mnemonic and communicative advantage it can also lead to a hyper-categorization of experience. That is why Eskimos label a dozen types of snow when in fact the composition of snow is always the same.
If, due to that neuropsychological mandate, we cannot break free of a dual signal system then we cannot conceive of an un-categorical phenomenon like quantum mechanics. Due to the human penchant for categorical drift we are forced to attribute the uncertainty of particle behavior to something. That "something" might have less to do with reality than with the evolution of the human brain (which, after all is designed to survive, not just discover).
In that context one could ask whether we even need labels to describe non-locality. Perhaps there is no such (material) "thing" as a photon. Its apparent capacity to operate as a wave or a particle might really pertain more to our cognitive dispositions than to the photon's nature. Our brains are finite and until we can soundly, experimentally verify a theory (bearing in mind that neither an atom, electron or a photon has ever been observed) we might be looking at nature through a neuropsychological prism.
The Particle/Wave Duality...
Another issue in physics is the apparent dual nature of reality - more precisely of matter. In various contexts a particle can behave like a discrete entity with circumscribed location and motion, yet at other times exhibit a wave property (which ameliorates its positional features as it appears to draw out and scatter probabilistically). It is an interesting quality that adds to the confusion in scientific circles. Once again, however this might be explained with Occamesque simplicity.
Consider the following hypothesis. A particle such as a photon or electron does not decay. Yet it has been established that all systems undergo entropy (decay) unless they are replenished periodically by outside energy sources. Even with that, entropy usually wins out due to the passage of time. That is because, among other things, those outside sources are finite and will themselves wind down. Thus, perhaps something inherent in the particle's non-entropic quality can address the duality problem.
One can begin by asking why a photon does not decay. One possibility is that the underlying source of entropy is time itself.
An example comes to mind. If a person could remain at a certain age - say 15, in year 1967, and that year extended into perpetuity he would never age. In that case an outside energy source would be unnecessary; first because he wouldn't need it, second because with no time lapse it would be impossible for "new" energy sources to be absorbed because a time lapse would be required even if just for one to open his mouth, bite down and ingest the new source of energy. Renewal, or counter-entropy implies a temporal sequence from depletion to energy restoration, which involves an event transition and a time lapse. Without a time lapse, there can be no entropy and no need or possibility to re-energize. In that context it might be time that ultimately determines entropy.
If a particle is traveling at light speed, it is moving neither forward nor backward in time. It becomes "constant" not only in terms of its unsurpassable speed but also as a chronological anchor point in the universe. Since it does not experience time lapses it cannot by definition be at one location at one point in time, then in another later on. While the "where" and "when" of human measurement depends on time passage massless particle do not recognize time passages. In the particle's range of experience there is no such thing as time.
Similarly, with no time elapse, there can be no spatial transition. That means the particle is what it is and everything that it is temporo-spatially; neither here nor there. It's dual nature is a simple manifestation of its para-chronological and para-spatial make-up. Theories superimposed on its behavior create closure, which satisfies the dual signaling system of the human brain, but might not reflect the non-spatial, non temporal realities of the subatomic world.
The Classical/Quantum Dichotomy...
It is understandable that physicists venture beyond parsimony at times in the attempt to unify classical and quantum physics. Perhaps because simple answers have been ruled more complex solutions are the only recourse. Yet our universe is undeniably systemic and as such it must be integrated on some level. The elegant stability of its various characteristics make that obvious. For example, just the right amount of matter overrides anti-matter to make existence (symmetry-breaking) possible. Another example is seen in the even distribution of matter and energy spread throughout the universe. Others can be seen in the spatial regulatory limits of the Planck length, Newton's inverse square law and the regulatory trick played on us by light speed which is so functionally stubborn that any possible differences in speed that might occur as a result of two people viewing an object in motion from different perspectives must lead to a corrective change in time lapse (time dilation) in order to hold "c" constant. All such mechanisms offer clear indications of a universe with a disposition toward stability.
The pervasive existence of cosmic order suggests there might be a congruent and/or co-functional relationship between quantum and classical physics (an idea implied by David Bohm via the hidden variables theory of quantum mechanics (Riley, 2010). Ultimately both the classical (order-based) and quantum theories must agree, and perhaps even be dependent on one another. Still physicists continue to grapple with the apparent discrepancies so it is worthwhile to discuss this issue further.
Information and the Pre-material Universe...
One way to connect classical and quantum physics is through a concept that simultaneously refutes and confirms both theories. It is found in an essential component of Information Theory. This bears some preliminary discussion.
Many theoretical physicists have referenced "information" in their writing, particularly regarding the behavior of black holes (Barbon, 2009). Information in that context typically refers to matter and energy. For example, if an object is sucked into a black hole, the object will break up, as seen in various Star Trek movies. Yet since the law of energy conservation holds that the energy of the object cannot be annihilated, can only change its form the info-energetic components of the object cannot disappear. In effect, all of the information content must continue to exist in some form. One reason why Stephen Hawking believed that radiation would materialize and radiate beyond the black hole (and not be completely absorbed) was that the law of energy conservation, combined with beneath-the-surface energy fluctuations that characterize a quantum state means that some of the information content - the stuff that popped in and out of existence (virtual particles) had to continue to exist, and to retain the information content of the mass that was absorbed into the black hole. More simply put; you cannot get something from nothing, or nothing from something. That use of the term information as applied to matter and energy is useful but possibly incomplete.
An Abstract Universe...
This writer has discussed this topic in previous articles but the idea is worth repeating. Information equates not just with mass and energy but with existence in every sense of the word. While theoretical physics assumes matter and energy are essentially all there is - thus the word "physics", there is a universal "something" that is not completely physical.
Information theory holds that "something" can only come into existence by being extracted from a prior state of monotony or uncertainty. The latter refers to a super blend without any internal distinctions, whether in the form of mass or force. The amount of information corresponds to the amount of uncertainty that is reduced. For example, if we type out the letters "tele"... and ask which word it refers to, answers would vary (uncertainty would be high). But if we add one letter at a time, each new letter (say initially the letter "p" it would reduce uncertainty by one bit. Now we have the letter sequence "telep." Still this can entail several possibilities so uncertainty still prevails, as does redundancy. If, however we add the letter "h", followed by the letters o... n... e. the word "telephone" emerges ( a kind of grammatical "creation"). At that point maximal information has been attained, while uncertainty is reduced to zero. In an analogous process this gives the idea of nothing a slightly different meaning.
Within that model each reduction in uncertainty..(i.e. each distinction extracted from redundancy item) creates a viable message... a "something" that can apply not just to language but conceivably to any aspect of nature.
In a cosmic context, "nothing" would equate with complete/infinite redundancy. For example, with no distinctions between a photon and an electron, between, plasma and matter, between a fermion (matter-carrying particle) and a boson (a force-mediating particle) there could be no existence; neither perceptible to the human eye nor with any functional or communicative properties.
By that process, perhaps the entire universe - its essence, its functions, its communicative features originated, not quintessentially in a big bang but more functionally through information expansion in process that could be called cosmic resolution.
In some ways this is coincides with the anthropic principle but goes beyond that to a broader world mechanism which can be discussed through another experiment (sorry about the redundancy).
Imagine a universe with no distinctions among particles, forces, stars, planets, flora and fauna; only an infinite blend. In that state nothing could communicate with anything else. Changes, adaptations, messages, force and mass variations, as well as symmetry-breaking would all be impossible. This redundant world would not just be in a permanent state of entropy. It would not be a "world" at all because only with a transition from a state of uncertainty to information can existence originate.
A Proto-physical Explanation...
In that sense, a bridge between classical and quantum physics might lie in information dynamics. Without the uncertainty of the quantum world there could be no classical, lawful world. In that sense classical and quantum physics might be complementary rather than contradictory. In other words, just as one cannot get information without a prior state of uncertainty, one cannot get the lawful classical world without it being extracted from the uncertain quantum world.
Room for Dissent...
There are several problems with this argument (I told you I was fairly ignorant on this subject matter). One is that it explains the universe in abstract, rather than material terms. In this model Information theory replaces physics as a prime frame of reference. Second, it transcends both the quantum and classical models by postulating a 'derivation' theory of the cosmos whereby one cannot have order without an initial state of disorder. That would seem to refute the typical order to chaos sequence implicit in thermodynamics. Another problem lies in the implication that something can arise from nothing, which runs contrary to the principle of energy conservation.
How to address such conundrums? It is not an easy task. Quantum mechanics has been not only verified by research but employed very effectively technologically. So have classical concepts - or else we couldn't not travel into outer space or use GPS systems in our cars. On the other hand so has Information Theory, both technically and mathematically. The notion that information is measured by a reduction in uncertainty is almost well established (Stover 2014).
Another potential problem is that this idea raises interesting questions about reality; converting it to something more metaphysical because origin and causation are considered pre-material. It is scientific in that information lends itself to measurement through the uncertainty reduction postulate but the ultimate unified theory is not a field or theory of quantum gravity but a non-material info-resolution process.
What About the Beginning?
How might one conceptualize the pre-informed universe? One way is by drawing a parallel between two forms of energy - potential and kinetic. Potential energy corresponds to mass but has no impact or communicative possibilities or any effect at all, without movement (which converts it to kinetic energy). Potential energy is a state of pre-existence with no cause-effect manifestations. Like potential energy the proto-universe might have been implicit, at least until one bit (the first distinction) of information was extracted from its absolute state of redundancy.
Once a distinction occurred and separated from the pack (electron, photon, helium gas etc.) something interesting would have happened. Not only would the information content of the cosmos have increased at that point, but through separation by distinction it became possible for the first foray into communication to begin. That is because only with a capacity for signal differentiation can there be a message. Thus the newly distinct particle/gas entities were at some point able to exert influence on each other where none existed before in the potential universe. That in itself would have led to more rapid signal distinctions. An information explosion would have unfolded into a plethora of celestial bodies (which could be equally categorized as cosmic bits). Eventually, the four main forces would have separated functionally.
From information to systemization and complexity...
As more distinctions occurred, more bits of information would have obtained. Atoms developed distinctions in the form of electrons, a nucleus, protons etc. as part of information proliferation. Massive clouds of gas swirled until gravity pulled some together into distinct galaxies, which entailed still more information (uncertainty reduction) in the universe.
The question is whether existence, as applied to the origin and evolution of the universe can be seen as an evolving information system. If so, the quasi-entity prior to creation would have to be described as somewhere between a physical and a pre-material world. Not "nothing" as with a vacuum, but "nothing" in a functional/communicative sense; governed most basically by a process encompassed in information dynamics, and ultimately manifest through a resolution process, not unlike the cognitive quest for discovery by those who study the universe.