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Can We Resolve Quantum Paradoxes by Stepping Out of Space and Time? [Guest Post]

The views expressed are those of the author and are not necessarily those of Scientific American.

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Next month will be the 100th anniversary of Bohr’s model of the atom, one of the foundations of the theory of quantum mechanics. And look where we are now: we still don’t know what the darned theory really means. One of the most radical interpretations (which is saying something) has got to be the so-called Transactional Interpretation, whereby particles send a type of signal backward in time. This past fall, University of Maryland philosopher Ruth Kastner published a book that tries to make sense of it. I’ve invited her to guide us through it.

In the June issue of Scientific American, physicist and writer Hans Christian von Baeyer describes the current state of “deep confusion about the meaning of quantum theory” and discusses one proposal—a denial that the theory describes anything objectively real—for rendering some of the quantum perplexities “less troubling.” Von Baeyer also lists several other possible interpretations, but leaves out what I think is the most promising approach.

The idea, known as the Transactional Interpretation, was first proposed by University of Washington physicist John Cramer in the 1980s and has its roots in the ideas of renowned physicists John Wheeler and Richard Feynman. This interpretation makes use of a concept known technically as “advanced action,” which is characterized not by the usual positive energy but by negative energy. Though it may seem counterintuitive at first, it turns out to provide a natural way to understand certain aspects of the theory that currently seem arbitrary or ad hoc, such as the rule for calculating the probabilities of measurement outcomes.

In the transactional picture, the entities described by quantum states, which are characterized by positive energy, are only half the story. The other half of the story is the absorption of those emitted states, which is accompanied by a negative-energy (advanced) response. Cramer himself compared his account to the handshake of a financial transaction: the emitted state is the offer and the response state is the confirmation. Absorption is the key to untying the interpretational Gordian Knot presented by quantum theory, which has given rise to such perplexities as the famous Schrödinger’s Cat thought experiment. It is absorption that collapses the quantum superposition and saves the poor cat from the fate of being both dead and alive at the same time.

Cramer’s original version of the interpretation, although promising, did not receive widespread acceptance. Physicists and philosophers had trouble making sense of advanced propagation, which is usually considered synonymous with back-in-time propagation and therefore seemed to raise the possibility of causal-loop paradoxes, such as being able to go into the past and kill one’s own parents. In addition, some critics felt that the notion of absorber was not well-defined. My research is aimed at resolving these types of challenges and providing a clear account of what constitutes an absorber. By incorporating principles from relativistic quantum theory, which were absent from the original transactional picture, I have been able to obtain a clear criterion for the boundary between the microscopic quantum realm and the macroscopic classical realm, which is the point at which collapse is overwhelmingly likely to occur (although the collapse process is fundamentally indeterministic).

My development of the Transactional Interpretation makes use of an important idea of Werner Heisenberg: “Atoms and the elementary particles themselves … form a world of potentialities or possibilities rather than things of the facts.” This world of potentialities is not contained within space and time; it is a higher-dimensional world whose structure is described by the mathematics of quantum theory. The Transactional Interpretation is best understood by considering both the offer and confirmation as Heisenbergian possibilities—that is, they are only potential events. That removes the possibility of causal-loop inconsistencies, since neither the positive-energy offer wave nor the negative-energy confirmation wave carries real energy, and neither is contained in spacetime. It is only in the encounter between the two that real energy may be conveyed within spacetime from an emitter to an absorber—and when this occurs, all the energy is delivered in the normal future direction.

The Transactional Interpretation, in this new possibilist version, provides not only a clear physical account of measurement but also a new understanding of quantum reality in which dynamic possibilities give rise to observable physical events through the transactional process. It also renders harmless the “spooky action at a distance” that troubled Einstein. Quantum correlations do not violate the relativistic speed limit because these correlations exist only at the level of possibility.

The transactional picture is conceptually challenging because the underlying processes are so different from what we are used to in our classical world of experience, and we must allow for the startling idea that there is more to reality than what can be contained within spacetime. As is evident from von Baeyer’s article, quantum theory truly challenges us to think outside the box—and, in this case, I submit that the box is spacetime itself. If this seems farfetched, consider the eloquent point made by physicist and philosopher Ernan McMullin: “Imaginability must not be made the test for ontology. The realist claim is that the scientist is discovering the structures of the world; it is not required in addition that these structures be imaginable in the categories of the macroworld.” Only if we face the strange non-classical features of the physical world head-on can we have a physical, non-observer-dependent account of our reality that solves longstanding puzzles such as the problem of Schrödinger’s Cat.

Images courtesy of Ruth Kastner

George Musser About the Author: is a contributing editor at Scientific American. He focuses on space science and fundamental physics, ranging from particles to planets to parallel universes. He is the author of The Complete Idiot's Guide to String Theory. Musser has won numerous awards in his career, including the 2011 American Institute of Physics's Science Writing Award. Follow on Twitter @gmusser.

The views expressed are those of the author and are not necessarily those of Scientific American.

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  1. 1. rloldershaw 11:06 am 06/21/2013

    I worry that we will never have an adequate understanding of quantum mechanics until the theory is recast in a theory that is consistent with general relativity.

    Such a revised QM modeling would require a relativitstic space-time that is fully background independent.

    When physicists resorted to unphysical Hilbert space and a probabilistic approach to modeling the atom, they achieved some nice model-building results that can reproduce observations, but this model may strongly deviate from the way that nature actually works.

    Robert L. Oldershaw
    Discrete Scale Relativity/Fractal Cosmology

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  2. 2. Simon Says 11:08 am 06/21/2013

    May I suggest you incorporate string theory into your ideas? M Theory might help as well. It is possible they exist outside the space/time continuum.

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  3. 3. Scienceisnotagenda 11:24 am 06/21/2013

    Hmmmm….outside of space/time. Therefore ‘anything’ that is thought up has validity. Not science but logic that only makes sense in an imaginary scenario. It’s akin to needing a wooden stake to kill a vampire…the premise for the theory is that vampires exist. Transactional interpretation needs a fantasy scenario to prove its own logic.

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  4. 4. And Then What? 1:43 pm 06/21/2013

    I like this. It fits with some of my own jumbled thoughts regarding what I have termed Negative Space-time and Negative Energy. Here is something I wrote in response to a question from another commentator, regarding a comment I made, on another site.
    “What you have to get your head around is that when you talk about Matter and Energy They are entities that we are easy for us to relate to because we can measure them and perform all manner of experiments on and draw conclusions about the observed results, but when we start talking about Space itself and Space-time that is another kettle of fish. We cannot actually observe Space and so we cannot say what Space is exactly there are probably as many theories as there are theorists. We can draw inferences from our observations of how Matter and Energy behave but that is about it, as far as I know, I could be wrong here and stand ready to be corrected by someone who is more informed than I. So back to your question: “In your thoughts, is the positive space Matter and the Negative space Vacuum? Or do Matter AND Vacuum exist on the positive-space side of your equation, with the Negative-space side being your theoretical construct of equilibrium?”
    Here is the best I can do: Positive Space would exist independent of Matter and Energy. Space is the “Fabric” in which Matter and Energy is imbedded. You have to think in more than 3 dimensions here but essentially Space contains all the different forms of Matter, and Energy that we can see and measure. So in a nutshell, Positive Space containing all visible and invisible Matter and Energy that you would normally think of would stand alone and Negative Space would exist independent of all this. Now of course there are many ways to visualize Negative Space. Perhaps it would always` exist alongside Positive Space, or perhaps it would only come into existence at the instant Positive Space is created and only then exert its effects. Then again Negative Space may have always existed and may surround Positive Space in an ever-expanding a cloud-like shell that grows in direct proportion to the accelerating growth of Positive Space and hence the force exerted on Positive Space grows exponentially as Positive Space Grows. I am not sure if this makes sense to you but if it doesn’t I will try to clarify as best I can. So I guess maybe the answer to your question is: what you are calling Matter and the surrounding Vacuum are necessarily parts of what we term our Universe and Negative Space is an “outside” of this but its effects are able to be felt and influence our Universe. This is probably not a good way of describing it but it is the best I can come` up with right now. Any way I hope this helps or, at the very least, I hope I have not given you a Migraine headache.”

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  5. 5. jtdwyer 2:42 pm 06/21/2013

    So Einstein could have resolved his issues with spooky-action-at-a-distance by accepting time inversion and negative energy? I suspect he would still have chosen: d – none of the above!

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  6. 6. tharter 2:45 pm 06/21/2013

    What makes Schoedinger’s Cat a ‘problem’? I have no issue with accepting that some things are simply not determined. Its really not conceptually different from any limited-information situation in human terms. The Universe is simply divided up into regions of space-time in which any given fact may be true, false, or indeterminate. Standing outside the box I find the cat’s state indeterminate. Meanwhile WHITHIN the box the cat is quite certain of its own state.

    There are simply 2 regions of space-time, one with a determined state of the cat and one without one. How is this different from say a relativistic situation where some region of space-time is outside the light cone in an observer’s frame of reference? Everything in that region is indeterminate WRT that observer. There’s no apriori reason to assign it any more ‘real’ a state than that of a quantum system we haven’t observed. Fundamentally both of these theories involve limits to what is determined in various regions. I don’t see one as being more problematic than the other, yet we don’t hear people wringing their hands about GR… Maybe they should be!

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  7. 7. And Then What? 5:55 pm 06/21/2013

    Actually I should have posted this original comment first, since it was what initiated the question from one of the other commentators:

    “Here is something else to run through you mind, if you get as bored as I sometimes do.
    What if we are being too self-centered in our views of what is taking place? Nature seems to love to create everything in pairs so that for every entity there exists a diametrically opposite entity to balance things out. So what if there exists a “Negative” Space which balances out our “Positive” Space. Now remember that by saying we exist in Positive versus Negative Space is merely a “convention”. So what does this mean, if anything?
    Well maybe just maybe what we believe to be an “outward force of expansion” is really an “inward force of attraction” exerted by Negative Space on or Positive Space. Our Positive Space may have once existed as much denser entity which is being ripped apart by the attractive force of Negative Space so that eventually both Positive and Negative Space will be neutralized into an infinitely stable space which would truly be Universal death. The difference here is that the driving force does not originate within what we call “our” Space but comes from the Universal desire for balance between Positive and Negative Space. I don’t know of any way to test such a hypothesis, so I guess this puts this right up there with String Theory.”

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  8. 8. kebil 6:40 pm 06/21/2013

    FIRST!!! I can’t believe it, I am the first to comment.

    Now bring on the critics, the freethinkers, those that “know” why this is wrong, and are just busting at the seams to tell us how the world “really” works.

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  9. 9. phalaris 6:32 am 06/22/2013

    Does this theory imply that a photon arriving at the earth from 10B-light years away “knew” what electron/atom it was going to interact with when it arrived here? Or that that electron was predetermined?

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  10. 10. arkajad 11:48 am 06/22/2013

    The book by Ruth Kastner states “Transactions are irreducibly stochastic collapses” (p. 57). Yet there is no stochastic process given that governs these transactions. And there is no term “stochastic” in the index. Therefore, I think, something is still missing. On the other hand there is an explicit stochastic process in the Event Enhanced Quantum Theory (EEQT) by Blanchard and myself. I think that a happy marriage of the two approaches is not excluded, provided one identifies our “classical events” with absortion-emission acts.

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  11. 11. juliajuli327 3:03 pm 06/22/2013

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  12. 12. MiguelHeredia 4:49 pm 06/22/2013

    I like the possibility of a “world” outside our reality.
    A question I’m asking for some years already is if our thoughts belong to our universe/to our reality. We can certanly imaging things that are not real or cannot be real at all (at least in this part of the universe) like jumping stones after they are heated (against the 2nd law of thermodynamics) or imaging us flying freely in the skies of N.Y. without any help. Is our mind also quantic? As mentioned above: I like these possibilities.

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  13. 13. gwmckenzie 5:23 pm 06/22/2013

    This has always felt to me a bit like the tail wagging the dog. If mathematics is a tool for describing the physics of events, it shouldn’t be confused with the actual event. Schrödinger’s Cat always seems like a very complicated variation of “If a tree falls in the forest …” The tree either fell (and made a noise), or it didn’t. There is a probability of either event taking place, but the probability isn’t the event, only a way of describing it. Now if I could just reconcile the twin slit experiment that easily …

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  14. 14. And Then What? 10:15 pm 06/22/2013

    Strange as it may seem, and as hard as it might be for those people who think that we know a great deal more than we actually do about our Universe, I would put it to you that we have only scratched off a very small hole in the coating that covers the window of Understanding. What I mean by this is, everything we, as a Species, have figured out about the workings of our Universe revolves around Matter and Energy and how it independently behaves and sometimes interacts. About the only thing we know for sure, to the best of my knowledge, about How Matter and Energy interacts with Space-time is that Matter seems to warp Space-time in proportion to the calculated density of the Matter in question or conversely Space-time reacts to The presence of Matter in proportion to the increase in Density of the Matter in question. Even this is probably a crude approximation of what actually is going on but it must suffice for now. The two dimensional analogy of this phenomena, while sufficient to crudely illustrate the effect is far from a proper description of the 4 dimensional Space-time reality of the effect.
    IMHO in order to advance our understanding of our Universe we will probably have to fundamentally change our approach. I believe that, if we are to significantly advance our understanding, what we call Matter and Energy should be looked at as what they actually are and given the importance that they deserve based upon their approximate percentage of the overall constituent parts that make up our reality. Don’t get me wrong they are an important piece of the puzzle as far as our understanding to date, but we may be fast approaching a threshold with regard to their usefulness in helping us to understand what is going on at the Quantum level, in particular. Perhaps we should be putting more thought into the liquid part of the soup rather than the bits and pieces that are floating around in it.
    The major problem with such an approach is that it will require a completely new paradigm as to how we think about our reality and our place in it. Just constructing the necessary Tools to test Hypotheses will not be an easy task. Never mind the mind-boggling mental task of constructing the Hypotheses to test, in light of our limited knowledge of the subject under observation. I would like to live to see how this plays out but unfortunately I will probably have to watch, and cheer from the ethereal sidelines.
    This, of course, presupposes that anyone will ever take up the task which will probably equate to smashing One’s head against the proverbial brick wall in a public square at Rush-hour.

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  15. 15. Mythusmage 12:04 am 06/23/2013

    How do we place ourselves outside space/time when we are space/time?

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  16. 16. pinetree 1:20 am 06/23/2013

    Never mind that useless cat, so there is a possibility that I am a genuis and a possiblity that I am idiot. Both will try do win the attention of the Absorber. And it’s random which one wins. Now that explains a lot about life…

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  17. 17. rekastner 1:22 pm 06/23/2013

    Actually, if we compare this to the “Many Worlds” interpretation — which has an infinite and more or less continuous splitting of spacetime into copies at every ‘measurement’ — my approach is a good deal less radical. One world, it’s just bigger than we thought. Our observable spacetime can be thought of as just the ‘tip of the iceberg’. The quantum level is beneath the surface.

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  18. 18. Chryses 5:20 pm 06/23/2013

    Are there any measurements that may be made or experiments that could be performed which would establish this as Science?

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  19. 19. S. N. Tiwary 4:31 pm 06/26/2013

    Paradoxes, in Quantum Mechanics, are amazing and weird but can be resolved going beyond space and time because everything happens in space-time.
    S. N. Tiwary

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  20. 20. Dr. Strangelove 9:50 pm 06/26/2013

    George, quantum interpretations are not science/physics. They are philosophy/metaphysics. They do not predict anything new. They just imagine observed phenomena in different ways. The key word is different imaginations, not different observations. IMO it is a waste of time for scientists to dabble with metaphysics. They should heed the words of philosophers. From Bertrand Russell: science is what you know, philosophy is what you don’t know. A better advice from Wittgenstein: metaphysics is nonsense. It is not nonsensical in itself but any statement about it must be.

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  21. 21. Narendra Nath 10:53 pm 06/26/2013

    Quantum entanglement is the hardest fact to comprehend, as it demands that if we talk of a single particle, it can be in either of two possible energy states or you need two particles system so that both the neighbouring quantum states get occupied by one each. The advent of Quantum (optical) computation will provide a choice state in between the two logic states to help decide which of the pair states gets occupied. Such a difference between the microscopic and macroscopic pictures make it tough to analyse a classical experiment to verify the quantum effects!Perhaps the answer may lie in cosmology about how the universe came into being or it always existed. Higgs God particle and its discovery relates to an event that follows in time scale well beyond the birth through Big Bang! The concepts that we have evolved about space and time may need alternative verification and confirmation about the homogeneity in space and time ever since the birth of the Universe through an anomaly like the Big bang creation! Uncertainty relations implicitly indicate that space and time anomalies can generate matter and energy. Thus, we need to know what content of matter/energy in the universe originated due to Big Bang creation anomaly and what got created due to non-homogeneity in space time!

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  22. 22. skeam 5:02 pm 06/27/2013

    I think it would be neat if absorption is what collapses superpositions. And I agree that we need to think outside of the usual time/space/locality “box” (since quantum mechanics does not seem quite compatible with it, whichever way you turn it).

    However, what exactly is it that is absorbed to end the superposition in experiments where e.g bigger particles like molecules have been in superpositions? Clearly, it’s not the entire molecule being absorbed in such a way that it vanishes, like a photon might be.

    Also, in the transactional model, in cases where the situation is not as neat as in the illustrated experiment with just two detectors, but rather with very many possible absorbers in many directions (like the detector screen in the two-slit experiment, or even some wave going out spherically in every direction), would that mean that every possible absorber around the emitter takes part in a transaction with the emitter? That seems enormously complex, although perhaps not totally inconceivable.

    Also, in the transactional model, does it not matter for the transaction mechanism if the distance to different possible absorbers is different? Can they still all exchange the transaction with the sender in order to select which one is going be actualized, and which ones vanish?

    Another thing I don’t quite understand with the transactional idea – but maybe there is some explanation – is that i seems to me there “should” also have to be third “round” where the detectors/absorbers are somehow “informed” of which one of the several possibilities is actually actualized and which are not. How will they otherwise “know” which one actually “wins” and gets the absorption and which ones don’t? Because in the description with the waves going back and forth, everything seems to appear just the same to all of the absorbers, with no way for them to “find out” who wins.

    Comparing this to a financial transaction with several parties involved, it would not be enough for just the sellers and the buyers to communicate their offers and bids, there also needs to be a way to communicate which one wins.

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  23. 23. edprochak 5:03 pm 06/27/2013

    This sounds very promising.

    My question is that it is not clear who is speaking the sentence beginning “My research …” in the fourth paragraph (between the two figures). Is it the article author, George Musser, or is it the person interviewed, Ruth Kastner?

    Just confused.

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  24. 24. debu 9:35 am 06/28/2013

    Space and time are not relativistic space-time as Einstein taught us. Time is entropical local time in the back drop of absolute nothing space occupied by ether called dark energy. So space is never empty but occupied by non isotropic dark energy composed of graviton and antigraviton swirling and whirling around masses in different proportion as per mass so that a permeability P is required in Newton law F=P.G.M.m/R.R . But graviton has mono magnetic coupling pushing masses on earth towards center of earth we call gravity. Anti gravitons are pushing space out for expansion. CERN recently found two Higgs Bosons ..they are graviton and anti graviton. Read the revised atomic model without strong and weak forces published by Durgadas Datta to understand mono magnetic coupling effect and gravity etc etc.

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  25. 25. Bryan Sanctuary 10:41 am 06/28/2013

    This approach is, I agree, challenging and requires some faith. I still think that the resolution of EPR, non-locality and quantum weirdness will be simple (KISS) when it is finally accepted.

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  26. 26. christinaak 8:28 am 07/5/2013

    I think this is another dead end approach to understanding quantum behavior, and I am losing hope that a sensible approach will be found in the near future.

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  27. 27. rekastner 5:11 pm 07/11/2013

    Some commenters have asserted that ‘everything is in space and time’ and that ‘we are in space and time’. Remember that to be ‘located in space and time’ means to be confined to a finite region, which certain quantum objects (such as quanta in momentum eigenstates) certainly are not. Moreover, a system of 2 or more quantum objects has more than 4 degrees of freedom, meaning that it cannot fit into spacetime which has 4 coordinates (x,y,z,t). Many researchers deal with this by saying that quantum states are not about reality and that they just represent our knowledge of a system. But treating quantum states as measures of our knowledge encounters serious problems (e.g. the PBR theorem). I offer an alternative approach: expand your conception of reality. (If you find this approach metaphysically extravagant, compare it to the far moremetaphysically extravagant ‘many worlds’ approach, which fares poorly in trying to explain the Born Rule for probabilities of outcomes.)

    As for this being a ‘dead end’, I invite commenter #19 to read my book before making that kind of assessment. Remember that all extant interpretations ignore absorption, and I claim that this is the missing key to the locked door.

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  28. 28. billinsandiego 2:24 pm 07/13/2013

    Reframing gwmckenzie’s use of the “tree falling in the forest” problem might be a way of looking at Musser’s solution. The tree falling does not actually make a sound – only the potential of a sound. The air as an “introducing” medium, then the ear that “absorbs” the vibrations, finally then the brain (the observing scientist), which interprets the absorbed potential as sound.

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