It's About Time
Is the Transaction Interpretation the 3rd rail of quantum mechanics, or is it about to make waves?
Heads-up
Because of the length of this article I’m including a tease here from what I think is the “payout” which comes toward the end (where it naturally belongs). So repeated here is the brief 15-minute excerpt from the Theories of Everything podcast interview with Avshalom Elitzur. The link to the full 2h 19m podcast is also included below.
“Quantum leap” is a phrase borrowed from science, specifically physics (besides being a fairly cool television show). It’s used in conventional speech to emphasize a change in something; not a trivial change, but one of great significance.
It’s ironic that its literal meaning from physics defines the very smallest change observable in Nature. A change in an electron’s orbit around an atom — a “quantum jump” — is one such example. The rub is that though these are among the smallest actions allowable by our present physics, what is actually going on in this tiniest of journeys poses the greatest mystery of the last hundred years and remains “natural philosophy’s” greatest challenge.
It has been a full century since quantum mechanics (QM) revolutionized our understanding of the sub-atomic world. Since that time the mathematical formalism behind it, a “don’t ask, don’t tell” process, has produced results of unrivaled accuracy; yet the debate over the underlying meaning of the mathematics — what it says, or doesn’t say about “reality” — continues unabated.
Some scientists, proponents of a so-called “transaction interpretation” (TI), believe our definition of “reality” now requires an upgrade. By excluding from “reality” the quantum realm that underlies our physical experience of observable, measurable events — e.g., the potential paths of a photon when passing through a pair of slits on its way to a screen — it is too rigid. They assert that a finer definition of “reality” is required to account for this “sub-reality.”
For years that undiscovered country has been consigned to a save-for-later category; to wit: the mathematical formalism used to penetrate it and produce measurable outcomes merely represents a measure of the observer’s knowledge, or lack thereof. This handwaving has held from the beginning of QM’s development a century ago, dubbed the “Copenhagen interpretation,” established by one of QM’s founders, Neils Bohr.
The Flow of Time
The element of time is one of the main stumbling blocks to a deeper comprehension. The quantum world appears to defy the notion of time as we experience it. A consensus may be forming that the quantum world is a separate “reality”; furthermore, one from which our experienced reality (“classical physics” concepts) emerges. In that sense, it may be more real. In this view, our sense of the flow of time is an emergent property of the quantum world, much like our sense of touch emerges from the interactions of electromagnetic fields, or our sense of hearing emerges from the displacement of air molecules.
Those metaphors are somewhat useful but they fail to capture the deeper relationship between the world of our senses and the physical reality that lies underneath. The physics behind our experiences of touch and sound lie very much in the comprehensible, physical world — the world of the electromagnetic field in the former and that of air molecules in the latter. Whatever lies underneath the observance of quantum effects such as a changing electron orbit or the mystery of “entanglement”… does not.
John Cramer, Ruth Kastner and Avshalom Elitzur are three physicists that champion a new interpretation of the quantum formalism; one that accepts the “reality” of quantum processes that defy the normal flow of time and appear to violate the speed limit of light imposed by Einstein’s special relativity.
John Cramer is the pioneer who first proposed the “Transactional Interpretation” (TI) in 1980 and coined “quantum handshake” in a 1986 paper. Ruth Kastner fine-tuned his model, and has proposed an enhanced interpretation which she calls the Possibilist Transaction Interpretation (PTI). Avshalom Elitzur has produced experimental results that appear to confirm the validity of time-reversal processes central to the thesis. Each of their contributions will be explored herein.
Be forewarned: delving into the various interpretations of what is really going on behind the mathematics of quantum calculations leads into more rabbit holes than the Kennedy assassination.
Nature’s constant reminder governing the quest for scientific truth, whether we call that a “theory of everything” or the “grand unified theory,” is this: the map is not the territory. We strive to continually refine the map, but it likely has no final perfect resolution. Philosophers may argue that the map can never become the territory. Human understanding has its boundary conditions.
One of those boundaries is time. Like a river, we are caught in its current. It appears to us to flow in one direction, from the ever elusive “instantaneous” present to the future, leaving in its wake, the past.
In his brilliant novel, Slaughterhouse Five (the movie is also highly recommended), Kurt Vonnegut tells the story of one Billy Pilgrim… who, we are informed in the very first sentence, has become “unstuck in time.” Pilgrim experiences his life in unpredictable and haphazard snapshots from its full journey. He knows how he is going to die because he has already experienced it — many times over.
However, Billy Pilgrim’s predicament echoes a sci-fi concept that is moored in a bona fide school of thought shared by many physicists (including the one whose work first made it tenable to the scientific community, Albert Einstein) — the block universe (aka block world, BW).
The Block Universe
One of the consequences of Einstein’s theory of (special) relativity was the rejection of any universal “now.” According to relativity, simultaneity is… relative. Two observers can disagree on the time ordering of an event external to them both; for one it may appear in the past whereas to the other it has yet to occur.
It takes no giant leap from rejecting the notion of a universal time-keeper to concluding that we may exist in a “block universe,” a higher-dimensional container of space-time where all events past, present and future all exist… at the same “time”?
Posit a fifth dimension, neither of space or time, where all events and their times (the four dimensions of spacetime: three of space plus the time dimension) are available to peruse. This would be Billy Pilgrim’s reality… with the caveat that he has no control of where he plops down into this block universe, at any one moment.
The consequences are profound if this true. Keep in mind that many great minds (such as Einstein and YouTube physics popularizer Sabine Hossenfelder) believe this to be the case — namely, all events in the universe are predetermined. It follows directly that there can be no such thing as free will. The notion that the choices we make every micro-second of our lives have already been mapped out for (by?) us is… unsettling, to say the least. It’s no surprise then that many physicists reject the block universe hypothesis on philosophical or religious grounds. Psychologically — and spiritually — it is a bitter pill to swallow.
I mean, what then, is the point of it all?
It should be noted there is a lo-cal version of the block universe, a “block-lite” if you will, which holds that the future doesn’t yet exist, but is in the process of constant creation. Only the past and present exist in the block.
Before comparing notes on the three physicists we need to become familiar with some of the well-established features and processes of quantum theory, particularly those that appear to violate our normal sense of the flow of time. A primer on waves, wave-particle duality, quantum theory and the wave function itself will be helpful. I will minimize technicalities and provide links for further explication. If you’re already familiar with these topics you may want to skip ahead.
Wave-Particle Duality
Wave behavior is familiar to us on terra firma from sound and water. We hear the sound from a pulsing speaker cone, moving air molecules which reach and tickle our eardrums. A pebble dropped in a pool produces visible waves. Drop another to see wave interference.
Video: Wave interference; makeshift double-slit demonstration
A wave is a disturbance — within a medium required for its transmission. With water waves, it is, obviously, the water. With sound waves, not so obviously, it is air molecules that vibrate and transmit the waves to our ears, there perceived as sound.
Light is Electromagnetic Radiation
The trouble began way back in the 19th century with the debate over the nature of light. Was it a particle or was it a wave? Depending on the experiment conducted it could be observed as either. Both sides were eventually forced into a reconciliation, accepting the awkward truth that light can be both wave and particle. The physically observable nature of light depends on how it is measured.
But when wavelike behavior is observed, what is the medium?
It took two decades into the 20th century to understand that light waves were vibrations in a field, the electromagnetic (EM) field. Consistent with all known wave behavior scientists assumed there had to be some material in some medium doing the “waving” in these fields. The hypothesized substance was termed the “ether”; the universe must be awash in an “ether wind,” it was believed.
Experiments to measure the speed of EM radiation (i.e., the speed of light) assumed that differences of speed, however slight, would manifest with different directions of its propagation with respect to the ether wind. When no difference was detected it became apparent that the speed of light, c by convention, must be universally constant.
There was no ether. EM radiation was revealed to be a thing unto itself, requiring no medium, and always traveled at the same speed (in a vacuum). Both discoveries were revolutionary developments, the latter led directly to Einstein’s (special) theory of relativity, and the former a foreshadowing of mysteries to come from investigations into the subatomic world. It would not be the last time that scientific experiments defied expectations, rebuking commonsense notions of how the world must work.
Video: Michaelson–Morley experiment
Quantum Theory
The development of physical theories historically have their origin in the mind. Einstein imagined how the universe would appear to someone traveling on a beam of light. It’s probably apocryphal, but Newton’s insights into gravity supposedly stemmed from speculating on a falling apple while reposing under a tree.
But quantum theory didn’t emerge from some scientist creatively pushing the boundaries to refine the map of reality. Instead, it evolved incrementally from the analysis of empirical data that didn’t conform to existing theories; for example observations of light emissions from excited atoms.
It was believed that in atoms, electrons, the source of electricity, orbited atomic nuclei similar to planets around the Sun. A change from a higher orbit, an excited state, to a lower one, expelled the excess energy in the form of EM radiation; i.e., light. Conversely, incoming EM radiation absorbed by an atom would propel an electron to a higher orbit. Any such change in orbit should produce an emission or absorption of light measured as a continuous change in energy. But this was not the case. The discrete wavelengths observed were at odds with the expectations from established EM theory. The data showed that electrons simply jumped from one orbit to another, emitting or absorbing energy only at precise discrete values, thereby never actually traversing the distance between the orbits.
The great scientific minds of the day struggled with this until Werner Heisenberg seized upon a new mathematical framework to explain the data. It is notable that his new theory, dubbed the matrix formulation of quantum mechanics, wasn’t arrived at by an insight into what might be happening with the electrons in the atom, but rather by examining the numbers from the data and searching for a predictive pattern. It took another scientist to recognize that the arrangement of the numbers configured a matrix, a familiar mathematical structure from the domain of linear algebra. The theory stemmed from the data.
Following the matrix formulation, Erwin Schrödinger developed an alternative formulation that was later shown to be functionally equivalent. In his view, electrons weren’t thought of as balls orbiting atoms like satellites orbiting a planet or planets around a star, but rather as standing waves, with only specific orbits permitted corresponding to specific wavelengths. He thought of these orbital waves as some kind of matter wave, moving through space and time carrying energy and momentum; a physical wave packet that coalesced into a particle (“corpuscles”).
Schrödinger was eventually disabused of this belief, leading to a consensus labeled the “Copenhagen interpretation,” a joint understanding between the founders: Heisenberg, Shrödinger, Neils Bohr, and Paul Dirac. It held that we should only be concerned with physical measurements that produce observable results. What the wave actually represents between measurable events (such as an electron jump resulting from the absorption of a photon) is fundamentally not knowable. Science shouldn’t speculate about what the wave actually represents; we should refrain from “looking under the hood.” This approach is often cynically derided as “shut up and calculate.”
Video: Heisenberg Uncertainty Principle; Superposition
Double-Slit Experiment
Certain facets of QM pose explicit challenges to our perception of time, pointing to another level of reality beyond what we are able to experience.
Video: Double-Slit Experiment - PBS Great Courses documentary
The famous double-slit experiment was first used to argue for the wave nature of light. Coherent light is passed through a barrier with two slits onto a screen forming the familiar diffraction pattern. But a most curious thing was observed when the light is slowed down to emit one photon at a time: the diffraction pattern is retained. Each seemingly random point illuminating the screen, one from each singularly emitted photon, eventually forms the familiar diffraction pattern. This is interpreted as the photon interfering with itself. The quantum mysteries deepen when an attempt is made to catch which slit the photon goes through. This breaks the wave nature and the diffraction pattern disappears. (The photon then assumes its particle nature and proceeds through the normal geometric path expected from going through one slit or the other.)
The strangeness went to eleven when Paul Dirac theorized that all sub-atomic particles such as the electron also exhibit this identical wavelike behavior, producing a diffraction pattern when run through the double-slit apparatus. This forced the realization that particulate matter also possesses a wave-particle dual nature. If sent through a double slit before hitting a detector screen, the wavelike nature in the form of an interference pattern is presented. If an attempt is made to observe the particle immediately after passing through the slits and before its detection, the particle nature is adopted.
Why should one particle emitted have a memory of previous ones, and “know” where to arrive at a point on the screen to eventually fill in a diffraction pattern? Is this a further indication that the passage of time is of no relevance to the quantum world?
The Wave Function
The state of an isolated quantum system such as an electron in an atom is described by a mathematical construct known as its wave function. By convention it is labeled by the Greek letter Ψ (psi). The wave function is used to calculate a probability of a particular characteristic of the quantum system (e.g., a particle’s location) at some future time. The process produces results that are unerringly accurate.
Distinct from other formulae describing physically observed, measurable phenomena, the wave function Ψ contains imaginary numbers. Imaginary numbers don’t represent measurable quantities. Right away this is a red flag. A mathematical trick is used in the formalism to produce a quantum calculation that is usable (i.e., a physical measurement). Ψ is multiplied by its complex conjugate[1] Ψ*, a process which always results in a real number[2] (i.e., measurable). This process is known as the “Born rule,” after physicist Max Born.
Note, this was a purely ad hoc development. There was no insight into what is actually going on within the wave to justify this mathematical operation other than it produced a real number. The complex conjugate of a wave function is its time reversal. Ψ* is the time reversal of Ψ. The real number produced from the multiplication corresponds to the probability of the outcome under investigation.
Since inception of the Born rule in the 1920s, this process and the reason why it produces correct results has been continuously questioned and debated. The Copenhagen interpretation’s answer is “shut up and calculate.” It works, and the entire process should be considered as a whole: a sub-atomic event; the wave function that describes it; and what is observed when a measurement is done. They are inseparable.
Entanglement and Non-Locality
“Entanglement” is another facet of QM behavior that apparently violates time as we understand it, namely relativity’s proviso that nothing can travel faster than the speed of light.
When two or more particles share the same wave function they are said to be entangled[3]. This means their quantum states are intrinsically linked; in essence they share the same fate. Performing a measurement on one instantly affects the other; the link holds despite the separation between them. The distance could be so great that to convey information between them would require faster-than-light communication. Such behavior is referred to as “non-local.”
The link between entangled particles can’t be explained by laws of physics as we understand them to operate in spacetime. This particular phenomenon is the source of Einstein’s objection to QM, famously referring to it as “spooky action at a distance.” This is the reason why some scientists, including Einstein, claim that QM is an incomplete theory. A casual internet search will show that the scientific community generally frowns upon philosophical flights of fancy, holding to the view that entanglement is not something to be alarmed about. Their arguments essentially boil down to “it is what it is” and “shut up and calculate.”
Sabine Hossenfelder also dismisses the “woo woo” of entanglement by comparing it to two cards, one labeled with 1, the other -1, each given to two people who are then sent off into space to a ridiculous distance apart. When one of them checks their card, they instantly know what is on the card of the other. No “spookiness” at all.
I’m fairly certain there are more physicists who reject Sabine’s interpretation than go along with it. The general consensus is that, to use Sabine’s metaphor, the cards are not established as 1 or -1 at the outset. The cards are in a state of indeterminacy until one of their holders takes a look. The cards exist in a state of “superposition,” being either 1 or -1, only to be actualized as 1 or -1 when a measurement is made, which “collapses the wave function.”
Video: Superposition
Again, a casual search on “entanglement” will show the diversity of opinion in the scientific community. I mentioned rabbit holes earlier. Among the many conundrums provided by QM, entanglement holds pride of place in this regard, along with the infamous “measurement problem,” which will be touched on shortly.
TI theorists recognize entanglement as a doorway into the hidden realm that underlies the one we experience, the one that physicists such as Cramer, Kastner and Elitzur acknowledge, and to a large extent, hold to be “real.” And TI does provide an explanation for it.
Many Worlds Interpretation
Before getting into the nitty-gritty of addressing the transactional interpretations I would be remiss in not mentioning one other particular, popular interpretation: many worlds (MW). This holds that in any quantum process, the wave function, which can include multiple possibilities of what may occur, never collapses into one observable reality in our spacetime. Rather, the universe itself branches into new universes, perhaps one for each possibility. This is the source of the multiverse hypotheses, so popular in sci-fi and superhero comic books and movies.
I find it difficult in the extreme to believe that every flit of thought that crosses my mind, every neuron firing while I think, creates a new universe, and that this is true for every millisecond of my waking and sleeping life, that of every other person’s life, and why not every animal’s life? Throughout the universe? Etc., etc.
If MW floats your boat, fine. How could it ever be disproved, or proved? I leave it there.
Transaction Interpretations
There have been several attempts to establish new interpretations of the mathematical formalism. Note, they are interpretations, not new theories; they do not change the mathematical formalism. The math used to extract quantum measurements is unchanged. None result in different predictions from the tried-and-true results; they merely offer new interpretations of what is actually going on “under the hood.”
Time Symmetry
What the transaction hypotheses share is the conception of time symmetry, meaning time reversal, i.e., from the future to the past. Every quantum event that results in an actualized, measurable event (e.g. a photon illuminating a point on a screen) is enclosed temporally and spatially by an emission event and an absorption event.
This is important: In the transaction view, both emissions and absorptions transmit waves that travel forward and backward in time. Due to the nature of wave interference, the waves that extend temporally and spatially outside the twin boundaries, (i.e., before the emission event and after the absorption event), cancel out due to destructive interference. What is actualized into a observable spacetime event is the result of the wave behavior between the two events; specifically, a handshake between the two waves: the offer wave (from the emitter) and a confirmation wave (from the absorber), forming an “actualized transaction” between them. In this scenario, what we experience as time, normal time that flows from past to present and present to future, actually emerges from the transaction, from the substrata of this deeper reality.
The notion of time-reversal field emission precedes TI. A 1946 paper from Richard Feynman and John Wheeler postulated time-symmetric radiation of electromagnetic (EM) fields. They proposed that an EM emission would split into two halves, each with half the energy, one radiating forward in time, the other backward. All potential absorbers would combine to match the emission wave resulting in doubling the forward emission and canceling the backward-in-time wave. Clearly, as you will see, this laid the foundation for (quantum) TI.
Three Interpretations Share Time-Reversal Feature
For a given experiment, a quantum wave function, Ψ (psi), will be found that solves the Schrodinger wave equation. Its complex conjugate, Ψ*, will also be a solution. As mentioned above, the two are then multiplied to produce the probability of an outcome, such as its location.
Video: Schrödinger Equation
Mathematically, Ψ* corresponds to the time reversal of Ψ. This corresponds to the time-reversed path of a particle from its detection/absorption to the time and place of its emission… from its future to its past.
In the standard Copenhagen Interpretation, the actual meaning of Ψ* is ignored, since traveling back in time is not acknowledged as something that can happen; it explicitly violates causality. The mathematics is just recognized as necessary for the formalism to produce a (real number) result, since the wave functions contain complex (imaginary) numbers. [Recall: a complex number multiplied by its complex conjugate produces a real number.] The real number that results corresponds to a “probability amplitude.”
TI interprets the time-reversal (confirmation) wave as not merely a necessary mathematical device, but a valid entity, and essential for understanding the mechanisms by which it all works.
John Cramer’s ‘Quantum Handshake’
John Cramer originated his “transactional interpretation,” aka the “quantum handshake” interpretation in his 1986 paper, “The transactional interpretation of quantum mechanics,” published in Reviews of Modern Physics. Cramer later produced an account suitable for general audiences in his 2016 book, The Quantum Handshake. [Note, the notion of time-reversal field emission precedes Cramer’s TI; he didn’t create it from whole cloth. Forty years earlier Richard Feynman and John Wheeler postulated time-symmetric radiation of the EM field[4], as noted above (“Time Symmetry”).]
In TI a quantum process begins when a source/emitter (e.g., an energy packet from an electron that has dropped to a lower orbit/energy state) sends out — to the universe! — an offer wave. Possible recipients (e.g., another atom) receive the offer wave and send back potential confirmation waves, which Cramer sometimes refers to as “echoes.” These potential confirmation/echo waves travel backwards in time, so the emitter receives them at the instance of emission. The offer wave chooses from the potential confirmation waves that one that best satisfies conservation constraints (such as conservation of energy, momentum, angular momentum, charge, parity, polarity, energy), and a quantum handshake is enjoined. Cramer later augmented his hypotheses to establish how a hierarchy among the echo waves is determined from which the offer wave makes it choice.
[In the scientific literature, the choice of names for the two waves seems to be somewhat awkward. The forward-in-time moving wave Ψ, is called the “retarded” wave. The time-reversal wave Ψ* is known as the “advanced” wave. I find these somewhat awkward and so refer to these by the other names used for them: “offer wave” (retarded) and “confirmation wave” (advanced) to describe Ψ and Ψ*.]
Cramer insists that the waves exist in 3d-space — but with respect to time, in what he refers to as “pseudo-time.”
The Measurement Problem
Another of the controversies in quantum mechanics is the role of the observer in the measurement of a quantum process. The famous Schrödinger’s Cat thought experiment is commonly used to illustrate it. The wave function describing a quantum state persists as long as it isn’t measured. Once an observation/measurement is made the wave function collapses and a physical event in space-time is observed. The role of the observer raises questions about consciousness, and its requirement for reality to manifest (i.e. the “observer-dependent reality” conundrum).
Video: Schrödinger’s Cat/Superposition
Cramer’s TI claims to solve this. Rather than an observer “making reality,” the transactional handshake becomes, in effect, the measurement, and hence, “reality.” The “making of reality” occurs whether or not a conscious being is there to observe it. It is the transaction, the handshake between offer and confirmation waves, that produces an event observable in the real world. Every observable event results from a transaction; but not every transaction must be observed (by a sentient being?).
TI answers all of the “unmentionables” of the Copenhagen Interpretation, including the almost mystical nature of quantum entanglement. In the quantum world, within the wave function of entangled particles, the distance between the particles hasn’t yet come into existence.
Since time is no barrier to these transactions, there must exist some realm beyond, below or outside, our experience of the passage of time. Cramer does not offer any hypotheses regarding the nature of “pseudo time,” but he includes this speculation in his book, relative to the choice of confirmation wave from which to form transactions:
Transaction formation hierarchy, simplification or not, has interesting implications for the structure of time itself in quantum processes. In some sense, the entire future of the universe may be reflected in the formation of each transaction, with the echoes from time-distant future events allowed the possibility of forming transactions only after the echoes from near-future absorbers have been weighed and rejected.
Ruth Kastner’s Possibilist Transaction Interpretation
Physicist Ruth Kastner also champions the transaction interpretation, and she has proposed her own model which she calls the Relativistic Transactional Interpretation, aka the Possibilist Transactional Interpretation (PTI). Kastner’s expansion can be found in several papers; her 2012 book, The Transactional Interpretation of Quantum Mechanics: The Reality of Possibility; as well as several YouTube interviews.
In contrast with Einstein who believed QM to be an “incomplete theory” because the mathematical formalism reflects behavior that violates established notions of how the world must work (locality, determinacy, causality… “God does not play dice with the universe”…), Kastner believes it is complete — we just need to listen and respect what the math is telling us. And what it is telling us is that an underlying “reality” of the formalism describes a world — indeed, a very strange one — from which our observed spacetime emerges. In her work she refers to it alternately as the “quantum sub-strata,” a “pre-epistemic,” and “pre-phenomenal” world — which should be considered “physically real,” though not an “actualized” world. It is a universe of possible actualized realities, “incipient transactions,” one of which emerges, for any quantum event, following an actualized “transaction.” This distinction between “physically real” and “actualized” differentiates her interpretation from Cramer’s. Whereas Cramer claims the wave function occurs in real space, albeit in a “pseudo time” framework, Kastner believes they exist in a “quantum land, behind-the-scenes realm,” and “not tagged to a time index.” The quantum sub-strata. She is fond of using a “tip of the iceberg” analogy to describe it.
Kastner draws the distinction between incipient transactions in TPI as physically real possibilities that exist in the mathematical higher-dimension Hilbert space, as opposed to mathematical artifacts in Cramer’s TI, necessary to compute an actualized transaction that becomes observable in spacetime. She labels the possible paths in a wave function as “sub-empirical” and “pre-spatiotemporal.”
More to the point, she views spacetime events that we can observe as emergent from the quantum transactions. As such, time itself is an emergent property from these underlying quantum sub-strata processes.
Kastner believes that the offer and confirmation waves are “not actually moving back and forth in spacetime,” they are “physically real processes taking place at the quantum level.”
Cramer has this to say about Kastner’s interpretations in a footnote in his book:
We note that Ruth Kastner’s “Possibilist Transaction Interpretation” adopts just this point of view and treats quantum wave functions as being real objects only in an abstract multi-dimensional Hilbert space, from which transactions emerge in real space. The possibilist approach is perhaps not incorrect, but we consider it an unnecessarily abstract roadblock to visualization.
Video: Theories of Everything: Retrocausality & The Transactional Interpretation of Quantum Mechanics. Ruth Kastner’s interview with Curt Jaimungal
Avshalom Elitzur’s ‘Two State Vector Formalism’
If you have gotten this far, you’re about to get your reward.
Curt Jaimungal is a science journalist who runs a YouTube channel, “Theories of Everything” (TOE) and writes a Substack under his own name. It was a chance appearance of a link to one of his YouTube videos in my news feed that prompted me to write this article.
I read about TI several years ago and it made an impact on me at the time, but the TOE interview with Avshalom Elitzur, titled “A New Theory of Time,” really knocked me out. I have excerpted the most mind-blowing 15-minute segment from it here, and also included the link to the full 2h 19m video.
Jaimungal has a natural talent for interviewing, unlike many in the business who have difficulty disguising who they really believe is the more interesting person in the room. He only interjects when it is appropriate, and often at the precise moment when, “wait a minute…” crosses your mind. He is equal to the task of fully comprehending the scientific and mathematical complexities presented by his erudite interviewees. A first-rate interviewer.
His interview with Avshalom Elitzur was at times spellbinding.
Elitzur does not march under the TI banner, though he acknowledges the overlap with Cramer’s and Kastner’s proposals. In the video he doesn’t mention a “quantum handshake.” He dubs his interpretation of what is going on in the hidden quantum realm, the “Two State Vector Formalism” (TSVF)[5].
Like Cramer and Kastner, he assumes the reality of the time-reversal wave function (aka state vector; constituting the second one of the two in the name) and that it holds a crucial place in producing the results that are observed when a quantum event becomes manifest in spacetime (i.e., observable).
He has taken matters further by running lab experiments, confirmed and published by a team in Japan, investigating behavior of the time-reversed wave function that have produced some astonishing results.
I will summarize them here, but watching the video excerpt is the surer and quicker way to understand what’s going on. I’ve screenshot his charts below, but Elitzur’s narration is really necessary to get the picture.
An interferometer is a tabletop laboratory device that splits a light beam into various paths using a light source, mirrors, beam-splitters (half-silvered mirrors), and detectors. Elitzur’s setup is essentially an interferometer nested within another interferometer. It has a photon emitter that splits into three possible paths with three corresponding detectors.
After running the experiment which results in one of the detectors being activated (detector 2, D2, from his video), the only path that could’ve been taken is clear from the diagram. He then examines the two other paths that terminate in detector 1 (D1) and detector 3 (D3).
These paths he identifies as “fake futures”.
He then runs the actualized “true” future detection at D2 backwards. As you can see from the diagram, it arrives at two possible locations: the actual true source from the photon emitter and a “fake past” that goes directly through the first beam-splitter (BS1) and off the interferometer. This paths is labeled as a “fake past.”
When D2 is activated it is clear that nothing could have traversed the fake paths, yet he has found that indeed, activity does happen within the fake paths – and it is very strange activity indeed.
Apparently in sections where the fake paths overlap, that is, the intersection where both fake futures and fake past paths would’ve traversed — and only where they overlap! — both a particle and a negative particle (dubbed “nega-particle”) appear for a very brief time. Elitzur claims the nega-particle is a new animal to physics, not the same as an anti-particle which has opposite charge (as a positron has to an electron), but negative mass.
A particle with negative mass would behave in an opposite manner to a normal particle. It’s response to a gravitational field would be opposite. When impacting upon normal matter it doesn’t impart a repelling force, but actually causes an attraction. Anti-gravity, anyone? Elitzur claims they have detected and measured just such a small attraction where the nega-particle impinges on the mirror in the apparatus. The mirror is attracted to the nega-particle.
Spacetime ‘Becoming’
Elitzur’s main interest seems to lie in gaining a better understanding of time. What, when is “now”? From the consequences of his TSVF lab experiments he has formed some ideas about the relation between the quantum world, spacetime and the nature of the universe. He rejects block world and many worlds, and like Kastner, he accepts that spacetime is emergent from quantum events. He believes that the universe is in a state of becoming; at each moment, space and time is being created. The future does not exist in some higher-dimensional space à la BW that could conceivably be visited by Billy Pilgrim.
To date, ELitzur is most famous for his “bomb experiment.” Given a bomb that is so sensitive that coming into contact with just one photon is sufficient to trigger explosion, the consequences of superposition can be employed to determine whether it is live or a dud without causing detonation. This is because in the quantum realm, even “false paths” register activity. Furthermore, in what he calls “quantum oblivion,” the memory of the event is wiped… from the universe. The past is actually changed. Watch the video to see Elitzur make his case.
Video: Theories of Everything: A New Theory of Time (complete). Avshalom Elitzur’s interview with Curt Jaimungal
Thoughts… Questions… Speculations…
It may come as a surprise that Many Worlds and Block Universe are now dominant beliefs within the physics community, and if we can believe Elitzur’s statements regarding the rejection of some of his papers, TI, TPI and TSVF are at best minority opinions and maybe even considered fringe. This might be attributed to the time-reversal aspects. Backward time may be too big an ask. It implies the negation of causality, and that may be a bridge too far for some scientists.
But if the apparent backward time behavior is a projection of a quantum sub-strata world “event” onto spacetime, I’m not sure that anything in TI really manifests as backward time-travel in spacetime. The weird appearances of the extra-particle/nega-particle in Elitzur’s experiment may seem to contradict this, but I’m not sure it counts as a manifestation of backward time travel. Is there really a violation of causality here? I’m not sure.
Maybe if confirmation of Elitzur’s experimental results are repeated enough, a critical mass will be reached and there will be a paradigm shift. TI makes sense to me on a gut level. And it provides answers for all those questions that remain unanswerable under the present interpretations, specifically the measurement problem and entanglement.
When I saw the nega-particle and its negative-matter consequences, the sci-fi nerd in me immediately flew to… anti-gravity? Flying cars? Finally?
Wouldn’t it be something if, assuming the nega-particle is verified, some clever monkey finds a way to exploit this almost (albeit) instantaneous, mirage-like behavior and harness it to engineer anti-gravity? If anti-gravity is ever realized, would its history point to this very experiment?
According to TI, our experience of spacetime emerges from quantum interactions. The next level of refinement of our map of reality then, is the acceptance that this thing we call time — that we can never really comes to terms with subjectively because our consciousness is inextricably linked with it — must emerge from quantum transactions. Emission and absorption gets somehow translated into temporally ordered events as they emerge to our “reality” in spacetime.
In this picture, actualized transactions in the quantum world create the “now” in spacetime, while simultaneously (?) spin off the past. How this can be reconciled with relativity’s apparently ironclad denial of universal simultaneity is, I believe, yet to be explained. Elitzur’s ideas of the big picture seem to get sketchy there. More work is needed?
A conundrum: We recognize the emission and absorption as two separate things or states, things that are observable in our world, thereby implying distance, and space. But what do they correspond to in the quantum world? In what manner are they separated in the quantum realm? From what do they emerge?
And another: In Elitzur’s experiment, this thing about only the paths of overlap between “fake” past and futures actually manifesting a “mirage” particle and its negative companion… Why is this so? What differentiates the overlap paths from paths that lie either on the “fake past” or “fake future” tracks?
It almost seems like rules in a game. Unsurprisingly, many of the tech bros subscribe to the “simulation” theory, that we live in an AI simulation à la The Matrix. This can be expected from engineers who are racing to produce generalized AI and believe it potentially leads to immortality. If consciousness is just a numbers game of neural connections, when their time is up they can just upload their “consciousness” into a synthetic humanoid robot.
But this brings up an important point. Right now AI is making phenomenal strides, and no one is willing to predict what its impact will be on humanity even five years hence. Recently it has advanced to the point where mathematicians are using it to write proofs of conjectures. (Actually, of a “lemma,” which is defined as a generally minor, proven proposition which is used to prove a larger statement.) Admittedly, AI has not provided a proof for any of the really difficult conjectures that have stymied mathematicians for ages … not yet, that is…
Once AI has reached, or surpassed, the genius of our greatest minds, how will it explain the mysterious world lying within quantum mechanics? What will be its understanding of time? This is something the scientific community should anticipate with bated breath … assuming the world hasn’t gone Skynet by then.
Some believe ultimate reality can never be constrained by and codified into a human-constructed language. Perhaps reality is not humanly comprehensible. Maybe it can be experienced at some higher level of consciousness; but that trespasses into the metaphysical, lying outside the realm of the scientific method.
Yet I am more inclined to subscribe to the “woo woo.” Our sense of “self” is more than a connection of neurons in a meat sack. Spiritual teachings from the East have always appeared to me as more sophisticated than Western religious traditions. Notwithstanding the cartoon nature of the Hindu pantheon and the belief in reincarnation, the spiritual metaphysics of their ancient writings have more common cause, in my opinion, with the revelations coming from science’s objective investigations into Nature, explicitly from the world of the quantum.
There is a piece of ancient wisdom from the East I once heard, and as time goes by its possible truth value seems to grow with these investigations into the quantum world:
The observer, the thing observed, and the act of observing… are all one and the same.
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LINKS
Book: John Cramer, “The Quantum Handshake: Entanglement, Nonlocality and Transactions”
Video: How the Quantum Eraser Rewrites the Past | Space Time | PBS Digital Studios (Delayed choice, Entanglement)
Video: Planck's Constant and The Origin of Quantum Mechanics | Space Time | PBS Digital Studios
Video: Quantum Entanglement and the Great Bohr-Einstein Debate | Space Time | PBS Digital Studios (wave function; entanglement; EPR; Copenhagen interpretation)
[1] A complex conjugate is formed by simply replacing every occurrence of i, the imaginary unit, with –i. (i is the square root of -1.) For an elementary primer on imaginary numbers, please read my Substack, “Imaginary Numbers for Dummies.”
[2] Ψ* denotes the complex conjugate of the wave functionΨ. The product of a wave function and its complex conjugate, Ψ ⋅Ψ*, results in a real number that represents the probability density of finding a particle at a given location and time.
[3] Entanglement can be induced by directing a photon to a half-silvered mirror, referred to as a beam-splitter. At the mirror the photon is split into one photon that is reflected and another that is transmitted through with no change in direction. The two photons are now in a state of entanglement.
[4] A 1946 paper from Richard Feynman and John Wheeler postulated time-symmetric radiation of electromagnetic (EM) fields. They proposed that an EM emission would split into two halves, each with half the energy, one radiating forward in time, the other backward. All potential absorbers would combine to match the emission wave resulting in doubling the forward emission and canceling the backward in time wave.
[5] The “state vector” is the complete mathematical representation of a quantum event. A wave function is derived from the state vector to investigate a particular property of the quantum, such as its position or momentum.
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