Intelligent Design

Time: Can time flow backwards in quantum physics? Maybe …

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In a Viewpoint article, “Weak measurements just got stronger”, for This Week in Physics ( April 27, 2009) Sandu Popescu, Physics 2, 32 (2009) In the weird world of quantum mechanics, looking at time flowing backwards allows us to look forward to precision measurements:

In 1964 when Yakir Aharonov, Peter Bergman, and Joel Lebowitz started to think seriously about the issue of the arrow of time in quantum mechanics [1]—whether time only flows from the past to the future or also from the future to the past—none of them could have possibly imagined that their esoteric quest would one day lead to one of the most powerful amplification methods in physics. But in the weird, unpredictable, yet wonderful way in which physics works, one is a direct, logical, consequence of the other. As reported in Physical Review Letters by P. Ben Dixon, David J. Starling, Andrew N. Jordan, and John C. Howell at the University of Rochester this amplification method makes it possible to measure angles of a few hundred femtoradians and displacements of 20 femtometers, about the size of an atomic nucleus [2].

[ … ]

Viewed from one angle, this story is all about fundamental philosophical ideas. Does the spin indeed have a value larger than 1/2 or is the result simply an error in the imprecise measuring device used? Does the spin indeed have both the x spin component and the z one well defined? And, above all, does time indeed flow in two directions in quantum mechanics? To be sure, the strange outcome of the measurement of Sπ/4 in this pre- and post-selected ensemble could indeed be obtained as an error in the measurement, an error in which the pointer of the measuring apparatus moved more than it should have. The explanation can be fully given by standard quantum mechanics, involving regular past-to-future-only flow of time. But the explanation is cumbersome and involves very intricate interference effects in the measuring device. Assuming that time flows in two directions tremendously simplifies the problem. As far as I can tell, Aharonov, Albert, and Vaidman hold the view that one should indeed accept this strange flow of time. I fully agree. Not everybody agrees though, and this is one of the most profound controversies in quantum mechanics.Viewed from one angle, this story is all about fundamental philosophical ideas. Does the spin indeed have a value larger than 1/2 or is the result simply an error in the imprecise measuring device used? Does the spin indeed have both the x spin component and the z one well defined? And, above all, does time indeed flow in two directions in quantum mechanics? To be sure, the strange outcome of the measurement of Sπ/4 in this pre- and post-selected ensemble could indeed be obtained as an error in the measurement, an error in which the pointer of the measuring apparatus moved more than it should have. The explanation can be fully given by standard quantum mechanics, involving regular past-to-future-only flow of time. But the explanation is cumbersome and involves very intricate interference effects in the measuring device. Assuming that time flows in two directions tremendously simplifies the problem. As far as I can tell, Aharonov, Albert, and Vaidman hold the view that one should indeed accept this strange flow of time. I fully agree. Not everybody agrees though, and this is one of the most profound controversies in quantum mechanics. 

Also, today at Colliding Universes, my blog on competing theories about our universe. (You can search it via the Search Blog box at the top left, beside the “B” logo.) :

Origin of life: The misnaming of the Great Oxidation Event – which maybe never happened, so forget your prof’s huffing way back when

Hubble Space Telescope: And awesome introduction

History moment: Moon landing recalled

22 Replies to “Time: Can time flow backwards in quantum physics? Maybe …

  1. 1
    Mapou says:

    Interesting. Thanks for posting this. I am always annoyed whenever I hear physicists talk about time flowing in any direction. The fact is that time cannot change at all, by definition. Changing time is an oxymoron. Why? Because changing time is sefl-referential. This is the reason that Sir Karl Popper wrote in Conjectures and Refutations that spacetime is Einstein’s block universe in which nothing happens! It’s also the reason that nothing can move in spacetime and that any talk of time travel through wormholes by the likes of Stephen Hawking, David Deutsch and Kip Thorne is pure hogwash. Crackpottery in high places! This truth has been known for over a century and it is a perfect example of why peer review in science is really a joke. It’s all about politics.

    It’s really not all that hard to understand. Velocity in space is given as v = dx/dt. Velocity in time would have to be written as v = dt/dt which is nonsensical because the units cancle out. One often hears that we are moving toward the future at 1 second per second but nothing is further from the truth. The truth is that there is only the NOW, the changing present. That’s it! Change is real. Time is abstractly derived from change.

    If those quantum physicists really understood the abstract nature of time, they would also understand why particle interactions are probabilistic and not deterministic as Einstein had claimed (God does not play dice and all that jazz). It would also save them from looking like so many crackpots in the eyes of those who do understand that time is not a variable. In a way, it’s refreshing to know that crackpottery is not just the exclusive realm of Darwinian evolutionists. All scientific theories should be criticized and they should be criticized incessantly and mercilessly.

    Read Nasty Little Truth About Spacetime Physics for more on this ingrained crackpottery in the physics community.

    Oh, by the way. Space (distance) does not exist either but that’s a different story. 🙂

  2. 2
    RDK says:

    Are you really trying to make the point that change in time is impossible because it is self-referential? Then I guess all of Kurt Godel’s work, Principia Matehmatica, and every math theorem ever made is automatically impossible and false just on the merit that it’s self-referential.

    And that website is obviously a joke. It’s so awful it’s actually funny how serious it takes itself while still sounding like it was written by a snotty high school creationist. I read down far enough to get to the part where it calls Kurt Godel a non-scientific, chicken-feather voodoo god, and then I just clicked off because it was kind of hard to see the rest of the website with tears of laughter flowing from my eyes.

  3. 3
    Mapou says:

    RDK :

    Are you really trying to make the point that change in time is impossible because it is self-referential? Then I guess all of Kurt Godel’s work, Principia Matehmatica, and every math theorem ever made is automatically impossible and false just on the merit that it’s self-referential.

    Well, if it is truly self-referential, it is obviously hogwash. One does not have to stop being a follower to see that. Even flaming zealots can think for themselves every once in a while.

    By the way, I am pretty certain that it was Newton who wrote Philosophiæ Naturalis Principia Mathematica. Godel is best known for his incompleteness theorem and for having advanced the laughable notion that the General Theory of Relativity allows time travel via a closed spacetime curvature. One can always identify a crackpot as soon as they claim that time travel is possible. It never fails.

    And that website is obviously a joke. It’s so awful it’s actually funny how serious it takes itself while still sounding like it was written by a snotty high school creationist. I read down far enough to get to the part where it calls Kurt Godel a non-scientific, chicken-feather voodoo god, and then I just clicked off because it was kind of hard to see the rest of the website with tears of laughter flowing from my eyes.

    Very funny. I’ll be sure to put a warning sign on the page soon to act as a repellent against those whose sensibilities are easily offended. However, if you liked the humor, be sure to click on the humor page the next time you visit. It’s a hoot.

  4. 4
    herb says:

    A haven’t read the Gödel stuff yet, but I find Mapou’s point about the block universe (which I am visualizing as a 4-dimensional spacetime-cube) quite compelling.

  5. 5
    Mapou says:

    RDK, after re-reading your message, I realized that you did not mean that Godel wrote Principia Mathematica. You must be referring to Russel’s and Whitehead’s PM. Sorry for the mixup.

  6. 6
    RDK says:

    No problem; I was indeed referring to Bertrand Russel’s work.

    Although I still don’t quite understand why people are under the impression that time-travel is impossible just because it’s self-referential? I can think of plenty of better reasons why time-travel is impossible, but self-reference doesn’t pop straight into my head.

  7. 7
    Mapou says:

    RDK :

    Although I still don’t quite understand why people are under the impression that time-travel is impossible just because it’s self-referential? I can think of plenty of better reasons why time-travel is impossible, but self-reference doesn’t pop straight into my head.

    The best reason is always the simplest and shortest one. Why go into long and convoluted explanations when a short sentence will do, eh?

    Let me add that if you cannot understand how self-reference is illogical, then I am afraid that this discussion has come to an end.

  8. 8
    Mapou says:

    Herb, thanks for responding. It is a well-guarded secret in relativistic circles that nothing can move in spacetime. It is not mentioned in most books (there is only one exception that I know of) on relativity because it destroys the connection of spacetime with physical reality that we were brainwashed into believing for close to a century. It is a lie that falling bodies follow their geodesics in curved spacetime. Why? Because spacetime is 100% abstract. It does not exist. Why? Because its existence would forbid change/motion. It’s very simple, really.

  9. 9
    herb says:

    Hi Mapou,

    Just so I’m clear on your position, I take it that you do accept that SR and GR make correct predictions in some sense.

    In other words, despite the fact that “spacetime” does not correspond to reality, it still can be thought of as a differentiable manifold mathematically.

    For example, if we were to track the orbit of a planet around the sun using our usual measuring devices (rulers and clocks, ultimately), and put all this information into the equations of GR, we would find the planet was actually following a “geodesic” in “spacetime”, even though the spacetime concept is absolute rubbish of course.

  10. 10
    Nakashima says:

    Mr Mapou,

    I think it would be clearer to say that world lines do not move, they simply exist. A particle would then be a slice through a world line at a particular value for t.

  11. 11
    Nakashima says:

    Mrs O’Leary,

    If information could flow from the future to the past in some useful way, that would open the door to a telic explanation of events. This could be an important area for ID researchers to develop further. Thank you bringing this news item to our attention.

  12. 12
    R0b says:

    Mapou:

    Let me add that if you cannot understand how self-reference is illogical, then I am afraid that this discussion has come to an end.

    Since the above references the discussion of which it is a part, it must be illogical. Even worse, it references self-reference, of which it is an example, so it must be doubly illogical.

  13. 13
    Frost122585 says:

    Nothing can deal with the results of the uncertainty principle. The micro level is beyond our ability to master as the observer impacts the observed in such a way that the exact location and momentum of the observed cannot be accurately reached.

  14. 14
    Frost122585 says:

    Therefore it may not be the continuity time that is the illusion, but the continuity of matter.

  15. 15
    Nakashima says:

    Mr R0b,

    Even worse, it references self-reference, of which it is an example, so it must be doubly illogical.

    Instead of quoting the Knights Who Say Ni, let me note that two illogics make a logic, at least one quarter of the time according to Mendel, or at least half the time according to Schrodinger (but you are never sure of which half).

    This concludes the silly portion of this program.

  16. 16
    Mapou says:

    Herb @9

    I believe that SR and GR make correct predictions only to a degree, because neither were derived from first principles. I don’t believe that they are physical theories in the correct sense of the word. They are mere math abstractions, not unlike Newtonian mechanics. Newton’s equations explained nothing either, somnething that Newton was humble enough to admit and Newton was not a very humble man. But he knew that all he had was a mathematical description. The relativists, by contrast, BSed the world for close to a century by insisting that they understood gravity and that it had to do with bodies curving spacetime and being force to move along their worldlines by said curvature. It’s all unmitigated BS, of course. In so doing, they retarded progress in our understanding of gravity for at least a hundred years.

    For example, if we were to track the orbit of a planet around the sun using our usual measuring devices (rulers and clocks, ultimately), and put all this information into the equations of GR, we would find the planet was actually following a “geodesic” in “spacetime”, even though the spacetime concept is absolute rubbish of course.

    Correct. Having said that, there is one thing about GR that I absolutely disagree with and it is the notion that gravity propagates at c. I believe that gravity is a non-local phenomenon and is instantaneously felt everywhere. By the way, Newton’s equations assumed that gravity was instantaneous. In my opinion, he was right. This explains why Newtonian gravity is so amazingly accurate. Just add speed of light consideration and clock slowing to it and it should be as accurate as anything else.

  17. 17
    Frost122585 says:

    I must also add about Godel that he was argueing for the ideaity of time- that time is connected to the behavior of physical matter. I actually think that Godel’s argument is cogent and sound. The problem is it is only a logical and mathematical argument. Time travel is possbile in anyone’s imagination- just like evolution is!

    It is a question of whether it has, or will ever happen that answers the question

    “Could” it happen?”

    I Could ask the question “could John Mccain have won the election last year?”

    Anyone can come up with a physical argument for anyhting. Our immigration is almost limitless. That doesn’t mean that the physics is good or bad in a time travel argument. We just need to watch out for our tax dollars being wasted on things like this and man made global warming which is also imaginary but supported with statistical computer modeling.

    We don’t know if it is possible- But all of our experience points to the answer being that it is not. There has been no time travels from the future or the past coming to us.

    So the quackery is not in all of the physical theories being put forth but in the minds of those people believing them as proof for time travel and accepting them as truth based on no evidence except a mathematical synthetic construct.

  18. 18
    magnan says:

    Mapou,”I believe that SR and GR make correct predictions only to a degree, because neither were derived from first principles.”

    Really, only to a degree? And what do you mean by from first principles? I am not necessarily entirely supporting SR and GR as true understandings of ultimate reality.

    See the following on an actual test of the Special and General Theories of Relativity (at http://www.phaenex.uwindsor.ca.....ew/261/255 ). Note the last paragraph.

    “Accurate clocks have provided important tests of both the special and general theories of relativity. The
    periodic rate of a hydrogen maser carried in a rocket to 10,000 km changed with speed and altitude by the
    amounts predicted by the special and general theories. In other experiments observers have measured the
    delays predicted by relativity for radio waves passing near the sun. Future improvements in the stability of
    clocks should make possible even more rigorous tests of fundamental theories.
    The most severe tests of general relativity have been those of Joseph Taylor and his associates on
    millisecond pulsars that are one member of a binary pair (two stars so close together that the period of their
    orbital motion about the common center of mass is typically 10 hours or less). Although these binary stars are
    too distant to be resolved with either an optical or a radiotelescope, their orbits can be measured with exquisite
    accuracy by the modulation of the pulsar rate through the Doppler shift as the pulsar in its orbit successively
    Taylor and associates found that the orbital period of the binary is
    changing by just the amount expected from the loss of energy by the radiation of gravity waves predicted by the
    Einstein general theory of relativity—the first experimental evidence for the existence of gravity waves. The orbit
    is measured so well that it tests the strong field as well as the radiative aspects of relativity. The measurements
    confirm the Einstein form of the general theory of relativity and leave little room for alternative theories.

    The ratio of the observed rate of change of the binary period to that calculated from the Einstein theory of relativity including strong field aspects and gravity waves is 1.0032 ± 0.0050.”

    Mapou “…there is one thing about GR that I absolutely disagree with and it is the notion that gravity propagates at c.”

    (later from the same paper):
    “In a sense, these binary pulsar measurements permit a determination of the velocity of propagation of gravity waves since the excellent agreement between observations and calculations disappears when the velocity of propagation of gravity waves in the theory is allowed to differ from the velocity of light c by more than 0.1%.”

  19. 19
    Mapou says:

    Magnan,

    GR predicts a lot more mass/energy for the universe than can be accounted for. You may disagree by conjuring up all sorts of voodoo nonsense like dark matter/energy but, in my opinion, that’s a blatantly obvious failure of the theory.

    By first principles, I mean that there is no physics in GR (nor Newtonian gravity, for that matter), just math engineering. True physics is about particles, their properties and their interactions. Everything else is either abstract or voodoo.

    Re: the rest of your message.

    Due to the massive and deceptive brainwashing that accompanied relativistic physics (see my earlier posts here) in the last century and the ridiculous extrapolations (time travel, wormholes and the like) that ensued, I cannot take anything relativists say at face value. Sorry.

  20. 20
    Frost122585 says:

    RDK is right on this one. Time is relative to the flow of matter and perspective. But what Godel got wrong and what RDK is missing here is that such examples of reversed material relationships creating a “seemingly” backwards travel though time are non-existent as far as empirical evidence- we don’t have evidence of it not for it- just mathematical and physical constructs that speculate about the possibilities of matter. A christian may explain this theologically by saying God designed time’s arrow so that time travel is not possible.

    One also has to deal with the problem of the grandfather hypothesis – if you went back and killed you grandfather what would happen to you? In Godel’s case the person from the future would still exist and possibly along side another version of himself. But is that really time travel then? If you cant change the present existence of the time traveler then hasn’t one only altered reality as opposed to only rewritten it’s results?

    Time travel in the Godel universe is not time travel because for Godel time is merely ideal and therefore dose not actually exist. This is important to understand.

    Godel was insane though make no mistake he had emtional, spirtual, mental problems- and he became overly obsessed with things that were not of reality (like time traveling). One thing that put him in the mental hosptial was his attempt to solve Contor’s continumm hypothessis which had to do with synthszing inifinte sets. It is now widely held that there is no solution to the continum hyptohesis but Godel went nuts trying to solve it- which is sad because things like infinity are concepts that transcned mathematics but he was fooled into believing in unsupported notions of reality.

    Make no mistake though, his incompleteness theorem is beyond brilliant. All of his serious mental problems happened after he discovered the theorem and he began to question everything including his own mental health. It was written by someone that he began to see the world as having a giant “not” in front of it. The incompleteness theorem is a mathematical, logical and overall philosophical masterpiece- possibly the greatest of all time. It is the highest logical extension of the liar’s paradox. Godel proved the truth of Platonism that mind is greater than a machine and that formal systems cannot contain the human rational mind- and later he would write nor could mechanics explain the human rational soul.

    Godel’s theorem is a close friend of ID.

  21. 21
    magnan says:

    Mapou (relative to the binary pulsar measurements and implications for the speed of propagation of gravity): “Due to the massive and deceptive brainwashing that accompanied relativistic physics (see my earlier posts here) in the last century and the ridiculous extrapolations (time travel, wormholes and the like) that ensued, I cannot take anything relativists say at face value. Sorry.”

    I guess you simply reject out of hand whichever observational data documented in the professional literature that doesn’t meet your requirements. I think a more reasonable approach would be to assume the astronomers weren’t lying about the data and the interpretation is valid to the extent that it is most likely unless an alternate more plausible interpretation is available. The penalties for outright fabrication are severe in science if it is found out, and most researchers are basically honest in my opinion.

    That given, I agree about the tenuous nature of claims of dark matter explaining the galactic stellar rotational velocity anomaly, for instance. A lot of such ideas are speculation brought on to bolster the current theory. Another area is the issue of the possibility of the existence of ether drift, supposedly dismissed by GR and the Michelson/Morely interferometer test. But the binary pulsar measurements stand, in my opinion, unless evidence is forthcoming that the astronomers committed fraud.

  22. 22
    Mapou says:

    Frost122585,

    I’m sorry, but my opinion is that Godel was a true blue crackpot and his incompleteness theorem is just self-referential nonsense. Godel himself had doubts about it.

    As an aside, not one of Godel’s supposedly awesome accomplishments is of any use to anybody. Not one is used in any technology or scientific process. The Godel phenomenon stems from a bunch of mathematicians engaging in a collective self-congratulatory orgasm, in my opinion. Future psycho-historians will dismiss the whole thing as a symptom of a chronic inferiority complex. LOL.

    But please, do not let my dismissive view of Godel bother you too much. It’s just one man’s opinion. And it’s not all that important.

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