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Backwards in Time?

Because it’s hard to argue with people once involved in Nobel Prize-winning work, I take Warren Nagourney (University of Washington) at his word. At one time Nagourney assisted Hans Dehmelt, the UW scientist who won the 1989 Nobel Prize in physics. Now he’s working with John Cramer on a project so bizarre that, as this Seattle Post-Intelligencer story reports, he understands it only faintly.

That makes Centauri Dreams‘ chances of understanding it all but infinitesimal. And because the work involves the paradoxical quantum behavior called ‘entanglement’ and implies communicating information backwards in time, it also conjures up memories of another man one hesitates to challenge. It was Einstein who called certain weird quantum behaviors ‘spooky action at a distance’ and cultivated a continuing distaste for the paradoxes of quantum mechanics.

These are formidable scientists, but then so is Cramer, and in a way he seeks to confirm something Einstein said a long time ago. Einstein didn’t like the idea that entangled particles like photons could affect each other no matter how far apart they were in time or space. Didn’t a signal have to pass between them? The Einstein-Podolsky-Rosen paradox, which describes this behavior, was created just to showcase what seemed to be an absurd situation. How could a measurement made on one photon affect the other instantly no matter how far apart the two particles were?

Nonetheless, the evidence for entanglement seems strong. Let me quote Cramer from the article:

“If you do a measurement on one, it has an immediate effect on the other even if they are separated by light years across the universe…If one of the entangled photon’s trajectory tilts up, the other one, no matter how distant, will tilt down to compensate.”

Doesn’t communicating require a signal? Einstein thought so. He also knew that signals don’t move faster than the speed of light. Quantum theorists have found ways to make entanglement happen that don’t involve communicating, but Cramer thinks entangled particles do ‘talk’ to each other. It’s just that the communications can go backward as well as forward in time. And Cramer’s new experiment will test the proposition.

Read the article for experimental details. If Cramer is right and the experiment works, he may be able to show that a signal was received 50 microseconds before it was sent. And Cramer, ever far-sighted (he’s a science fiction writer as well as a scientist, and well known for his fine Alternate View columns in Analog), talks about implications like manipulating a Mars rover in real time — no speed of light delay.

Thanks to Tim Jones for reminding me about this experiment, and for making a good point that follows from it:

“I suppose the question would be whether to throw in the resources necessary to try and develop a single, killer technology like (quantum) teleportation that might solve the problem of long missions, or assume such research too financially risky and unlikely to succeeed, and press on regardless with the current paradigm.”

It’s always a tough call, and I think the answer remains that both avenues stay in play, though clearly, unless there are major breakthroughs, the longshot technologies will receive a minute portion of available funding. In terms of interstellar flight, we always bear in mind that the sudden insight may change everything, but in the meantime, we know the physics of forseeable missions (at least to nearby interstellar space) using sails and ‘Sundiver’ trajectories (a fine Gregory Benford coinage), about which more next week.

Comments on this entry are closed.

  • philw December 2, 2006, 10:15

    If Cramer’s experiment signals The Hive that we’re here I’m gonna be pissed at him.

  • andy December 2, 2006, 12:19

    As I understand it, quantum entanglement cannot be used for communication without sending a classical signal, which means that even though the entanglement would have an instant (whatever that means) effect, you’d still need to send classical information to take advantage of this, restricting transfer of information to slower-than-light.

  • Edg Duveyoung December 2, 2006, 12:29

    Each person on earth knows about quantum entanglement.

    I have created quantum entanglements MILLIONS of times. So have you.

    Howzat, you ask?

    Consider your dreams. What are the “laws of physics” in dreams? I can have a dream in which I am standing on earth and then instantly be on Mars in my next thought. Sure! No one here would gasp at this. Perfectly okay. Not breaking any dream-rules at all, right? In my dream, I can meet a physicist and ask him/her about this. He/she won’t be concerned that I’ve broken the speed limit of light and landed on Mars so quickly. He/she won’t be bothered that I would have had to travel the 140,000,000 miles at Star Trek warp speeds many times the speed of light. It’s commonplace in dreams to “be anywhere instantly” at the speed of THOUGHT.

    Consider that in your dreams your brain manufactures an entire universe instantly, and can change anything about it on-the-fly, and everything obeys “laws” perfectly. Laws? Well, for instance, if I dream about a person wearing a red coat, it’s pretty much assured that that person will be wearing a red coat in the “next scene of the dream.” A generalish rule, ya see? Well, who’s enforcing all these rules? Your brain, of course. Continuity is the bread and butter of brain functions. “Things,” even in dreams, must “stay the same” if they’re to “make dream plots possible,” right? If I throw a ball to my friend, Tom, in the dream, my next THOUGHT will almost certainly be of me seeing Tom, still dressed in his red coat, catching the ball. Sure, it could suddenly be Shirley Temple with four arms catching the ball — if the brain wants to do that — but continuity is good thing most of the time, right?

    Continuity. Rules. Instantaneous continuity. It’s merely a common feature of dreams. If I’m dreaming that I have an electron spinning one way and its entangled partner spinning the other way, who’s going to be amazed that I can dream about them being light years apart and still doing exactly the opposite of the other instantaneously? No one. There won’t be any dream physicist complaining that this phenomenon is “magic of some sort,” action at a distance of some sort. There won’t be a mad scramble to invent newer faster particles that allow the two electrons to communicate to each other what changes must be made to keep them dancing together. Everyone who dreams knows this is no miracle, because the brain is the one single source of everything happening in the dream, and it has omnipotence in this regard — it can do whatever it wants to do.

    I submit that today’s physicists are seeing just this. They’re seeing the abyss, the unknown beyond the known, the space beyond all stars, the silence between two thoughts in the mind of God. Can’t the mind of God dream also? Maybe dream up a universe like ours with every detail in perfect position? No problem for an omnipotent God, right? God could decide that quantum entanglement is a fact — give it continuity in the dream — and since God is all places at all times and can do anything, well, it’s nothing at all to keep two electrons as a matching pair.

    Mystery solved. Ain’t no tachyons at work here. Nope, no need for them.

    Newton said, “Hypothesis non fingo” — I make no hypothesis. He just didn’t want to handle that “action at a distance” and “what the hell is space” problem. Couldn’t get his massive intellect to find a way to grab onto it. Perhaps he knew about this “dream continuity” thingy. He knew that his cup of tea was empirical and to heck with forming theories about it.

    This is why the observer messes up the observing process at the quantum foam level. Your mind and God’s mind begin to interweave. What your THOUGHTS are will be revealed to you as you’re coming “out of the void between two thoughts” just like those two electrons dart in and out of the virtual field. Do you know your next thought? Is there a committee meeting about what your next thought will be? Have you ever been part of the design team for your next thought? Your next dream? Your present life?

    There’s no shame, you wonderful gigantic minds out there doing very good science, no need to bow your heads. The mystics stop at this doorway too. Everyone stops here. Concepts are not allowed to enter. Who here will bother to write a treatise that wonders about how “the guy in my dream last night is still is found to have a red coat in my dream tonight?” No mystery.

    It’s the aesthetic of God we see when we measure the laws of physics in action. Why is there quantum entanglement? For the same reason that roses are red — it’s what was wanted by an omnipotent mind.

    Mysteries happen when we see delicately into reality and find out that it’s as mutable, as arbitrary, as free to be anything as our nightly dreams.

    We’re riding on the whims of God, I tell ya!


  • Zen Blade December 2, 2006, 12:51

    What the heck is Edge babbling about?
    I’m having a hard enough time understanding the whole back in time signalling things….

    so, does this mean if we had a piece of equipment at Alpha Centauri, and we wanted to communicate with it, the communication would travel back in time at a constant speed (be it speed of light)… meaning that if we sent something at light speed to Centauri, we would expect an instantaneous response because the response would be sent at the speed of light… in reverse time??

    I’ve got to think about this some more.

    and btw, dreams are limited to your brain’s experiences/knowledge.
    -Zen Blade

  • Edg Duveyoung December 2, 2006, 13:27

    Zen Blade,

    So, you say, “dreams are limited to your brain’s experiences/knowledge.”

    To me your words are poetry.

    Care to elaborate on why you make such an astounding statement when history — even your own personal history — is filled with moments when the thought-experience is so novel that there is no way that that could have been emergent but instead is mystical? It is the common experience that our thoughts feel “brand new” and never before thought quite exactly so.

    I understand that you want certainty. We all long for it. But there’s a child prodigy born every 1,000,000 births that will make it ever so difficult to suggest that that person’s brain is strictly limited to past experience. You’re saying your nightly dreams are all the products of your past experience? You’ve never had a single thought or dream in which you found yourself scratching your head wondering where “that stuff” came from? If everything’s that crystal clear to you, then you should have your brain examined — could be you’re a miracle, a demi-god, yourself!

    For me, every single thought I have is an unsolvable mystery. I have quantum thoughts, ya see? Can’t nail those suckers down enough to say for sure where they’ve come from. But if you have such clarity, if you KNOW that all your thoughts are from past experiences, then you’ll be a world teacher if you can “make your case” about that. Otherwise, I’m thinking maybe your ego, like mine, loves causality because, well, then the ego can be a causer doncha know? A force to be reckoned with. Not merely a notion in a dream of God.

    And, if I truly knew what I was talking about, I’d be a world teacher too.

    The folks with the sharp pencils are trying to make the math work so’s to understand quantum entanglement. Godel said ya can’t always do that. I think that the math of physics is reaching the Godel-point when it seeks to conceptualize quantum entanglement. You can’t get there from here using concepts, words, formulae. The truth is beyond the system’s ability to express it.

    I’m just playing around here. Love your name by the way.


  • george scaglione December 2, 2006, 14:47

    i am a lucky man to be able to speak up in such a place as this.such a group as this.you know in the movie contact,how jodie fosters character has a friend who is a “man of the cloth”,”almost” as he claims. i hope everybody follows.but if you have seen the movie contact or read the book you will…so this character says “i am a man of reasonable intelligence,but this,my intellect can’t touch this” well friends thats how i feel at this moment. i suspect we all do.if anyone can say more in a fashion which actually would EXPLAIN more i hope to read that in the near future!? this is wonderful stuff and perhaps we are on the cutting edge of REALLY MAJOR BREAKTHROUGHS!! i want to read more my friends please share your thoughts.this kind of thing is the very reason i go online. i seek to understand more. that is all i can say for now,i hope to read alot more soon. respectfully my friend, george scaglione udt109@aol.com if you prefer

  • Ron S December 2, 2006, 17:30

    “If one of the entangled photon’s trajectory tilts up, the other one, no matter how distant, will tilt down to compensate.”

    It’s this wording that implies causality that troubles me. As Andy states there is nothing that travels faster than c so far as quantum mechanics is understood. The entanglement may be no more than constructed correlation in the creation of the photons. That is, no signal is required between photons when one is measured. Of course, if one insists that there is no correlation between the photons (statistically independent) the implication is that there would be a signal of some sort (odd as that may seem) between them when the first is measured.

    Ok, I’m no expert so I have to tread carefully here, but this is what led Einstein and others to conclude that quantum mechanics is incomplete or not fundamental. Whether it be hidden variables or something else in there.

    I am dubious that anything much is in this, although who am I to say. What I would claim is that rampant speculation based on this experiment is very much premature. We are stuck with physics as we know it until proven otherwise.

  • Adam December 2, 2006, 19:37

    Hi All

    Edg is *kind of* right. We make entanglements all the time – but it’s within our bodies and brains. Even in a ‘noisy’ thermal environment some aspects of quantum systems can be entangled for significant lengths of time.

    The thing with the new experiment is that it cracks open the door on retro-causality, just a bit. I often wonder if a quantum system as big and complex as our brains might allow even further retro-chronal signalling, acting as an amplifier, that the experience of deja vu and precognition is telling us something important about the nature of mind and brain.

  • Adam December 2, 2006, 21:25

    Hi Ron

    Cramer’s a lot more cautious than we spectators, refusing to speculate on conclusions, confining his speculations to SF magazines.

  • george scaglione December 3, 2006, 12:31

    this is a very heavy subject to which i will continue to lend an eye,i hope i will hear and see more.whoever would not mind e mailing me about any of this i can be reached as i say at udt109@aol.com thank you very much either way your friend george scaglione

  • Eric James December 3, 2006, 13:45

    Just a question:

    If a photon is moving through time from point A to point B, doesn’t it seem logical that reversing time would also reverse the direction of travel? That is, if it’s going back and forth in time. wouldn’t it simply go back and forth in space?

  • Ron S December 3, 2006, 15:43

    Eric, I’ll attempt a short response, keeping in mind that I am not a physicist.

    In classical dynamics motion is *defined* as a a change of position with time. Then we can consider whether there is a similarity or identity between the cases where a photon goes from A to B and where a photon goes from B to A in the reverse time direction. They can look the same – there is symmetry.

    One path to follow that might be insightful is Feynman diagrams. Interactions in the reverse time direction are part of these graphs. I did a quick scan of the Wikipedia entry and it seems like a reasonable place to look for more info.


  • Eric James December 3, 2006, 19:25


    This brings up an interesting question in regards to time. Theorists often wonder why time progresses so smoothly in GR, but not in QM. I’m wondering if this assumption is incorrect.

    We know of time reversals in QM because it’s simply part of the theory and the math. We don’t actually experience these time reversals. One might then wonder what are the particles in question experiencing?

    This brings to mind some rather profound questions:

    If time stopped, how long would it stop for? How would we measure it?

    If time reversed, how far back would we go? How would we measure it?

    Our only ability to measure time is in the forward progression due to causality.

    Let’s say we want to measure the length of a board. We grab a tape measure from our toolbox and measure the board, right? How might we measure it if time is reversing? We might start at the point of measuring, but in the end we would simply unmeasure it, put away our tape measure (moving backwards) and unlearn the knowledge of having ever measured it to begin with. If time reverses again, we’d have to start all over again.

    Therefore, it can be concluded that time can only be experienced linearly, even though it need not be linear. Time could run back and forth repeatedly (like a busted VCR) and we’d never know it.

    Of course this brings up questions related to deja vu’, but this gets too philosophical for my taste. For me it’s enough to understand that in our experience time must always appear linear, even if it’s not. Of course this doesn’t mean that time isn’t smooth, it only means that it might not be smooth (but it doesn’t matter).

  • Steven December 4, 2006, 6:39

    If two particles are entangled, it means that they are ‘connected’ somehow and therefore, no signal is required. I’m not particularly good in analogies but I’ll try and use one: If you imagine spraying water out of a hosepipe and whipping the pipe up & down, you will see delays in where the water drops. (if you whip the pipe up, the stream of water will still be on the ground and visa versa)

    Imagine now that the waterstream is frozen solid. Now there wont be any delays if you whip the pipe up and down. When you whip the pipe up, the other side of the ‘frozen stream’ will instantaneously whip up as well. If you have access to a library I suggest you read John Gribbin – In search of Schrodinger’s cat for a detailed explanation on entangled states.

    The discussion on time: Just as Ron stated that he is not a physicist, I must concur. I only read science books and online journals and with knowledge gained from that I can supplement this discussion. Time coexists with space according to Einstein’s theory of general relativity. Therefore a particle going back in time should traverse backward in space, but as Ron noted; these transitions are symmetrical.

    According to Machio Kaku in his book Hyperspace, particles don’t travel back in time per se, but pop in and out of existence without traversing space/time. Particles pop out of our Universe(our space and time) and into a Multi-verse and then back in our Universe again. In doing so the particle pops back into our Universe at an earlier time-slice.

    A few cosmologists including prof. Stephen Hawking postulates that our experience of time is due to the expansion of the Universe. And that when/if the Universe contracts we will experience time backwards. I find that hard to conceive but every thesis/hypothesis/postulate and theory must be entertained until negated.

  • Ron S December 4, 2006, 21:48

    Just like us, physicists enjoy speculation. Whether a Hawking or a Kaku. Most of these speculations, naturally, go nowhere. Usually we tend to only remember the ideas that work! In this regard, I remember that Hawking pretty much gave up years ago on his idea that time, and maybe how we experience it (whatever that means), would reverse if/when the universe contracts.

    Another area is when we extrapolate theories (i.e. mathematical models) well beyond the domain in which they have been, or might ever be, tested by experiment/observation. Lumpiness of time at exceedingly small scales is one example of this in quantum theory, as is the singularity and tachyon in relativity theory. These may be no more than artifacts of the mathematics when pushed into domains where they no longer apply. Sort of like pushing Newtonian dynamics into the realm of the very fast and massive.

    Regarding time experience, yeah that’s a juicy one, Eric. I kind of like the way Richard Dawkins thinks about it. Hopefully I’m paraphrasing him correctly when I say he says that we have evolved to experience time, space, matter and energy in ways that promote our survival. One example he gives is a rock’s solidity. Despite it being almost entirely empty space (just widely scattered electrons and nuclei) we perceive it as solid since it’s a time tested survival tactic. Or in other words, kicking boulders impairs our survival. As another silly exposition of this idea, we perceive time flowing ‘forward’ since we could become somebody’s lunch if we experienced time as moving, um, sideways. Sideways thinkers were culled, thus leaving forward thinkers to continue evolving.

    Take that for what it is or not as you please! It’s hard to know what to do with these sort of speculations. I don’t have the expertise to comment further.

  • Adrasteia December 8, 2006, 4:00

    If time stopped, how long would it stop for? How would we measure it?

    Obviously not in units of time.

  • Stephen December 11, 2006, 14:15

    I picked up a time machine at Best Buy a few years ago (or may i haven’t done that yet – i get so confused). It’s got one of those acronyms that isn’t explained. Maybe you’ve heard of it – V. C. R. I’ve no idea how it works inside. Maybe it uses these entanglement thingies. But, anyway, i mostly use it to go into the past. You know, when they used to make really good TV shows, like Gilligan’s Island.

  • george scaglione December 14, 2006, 13:52

    you know i do know that alot of people have difficulty with the concept of transmitting a message into the past.me too my friends but i’d like to hear more though.just yesterday saw a star trek i believe from season one where they encounter an advanced space craft from an advanced race where the whole thing keeps shifting between dimensions!! really cool yes but … i’d appreciate anyone who could take a crack at explaining that too!!!?? regards your friend george

  • ljk March 7, 2007, 17:18

    Time Travel – Not Possible?

    Mathematically one can go backwards or forwards in the three spatial dimensions. But time doesn’t share this multi-directional freedom.

    “In this four-dimensional space-time, you’re only able to move forward in time,” Liu told LiveScience.

    Full article here:



  • ljk April 10, 2007, 9:58

    Did time begin? Will time end?

    Authors: Paul H. Frampton

    (Submitted on 9 Apr 2007)

    Abstract: Did time begin at a Big Bang? Will the present expansion of the universe last for a finite or infinite time? These questions sound philosophical but are becoming, now in the twenty-first century, central to the scientific study of cosmology. The answers, which should become clarified in the next decade or two, could have profound implications for how we see our own role in the universe. Since the original publication of Stephen Hawking’s {\it A Brief History of Time} in 1988, the answers to these questions have progressed as a result of research by the community of active theoretical physicists including myself. To present the underlying ideas requires discussion of a wide range of topics in cosmology, especially the make up of the energy content of the universe. A brief summary of my conclusions, that of three different possibilities concerning the history and future of time, the least likely is the conventional wisdom (time began and will never end) and most likely is a cyclic model (time never begins or ends), is in the short final Chapter which could be read first. To understand the reasoning leading to my conclusions, which go against the views in other books on cosmology but which I think are likely to prevail, could encourage reading of this entire book.

    My hope in writing this, my first popular book, is that it will engender reflection about time. Many a non-scientist may already hold a philosophical opinion about whether time begins and ends. This book’s aim is to present some recently discovered scientific facts which merit the reader’s consideration.


    63 pages latex


    Astrophysics (astro-ph)

    Cite as:

    arXiv:0704.1132v1 [astro-ph]

    Submission history

    From: Paul Frampton [view email]

    [v1] Mon, 9 Apr 2007 17:09:10 GMT (75kb)


  • ljk May 28, 2008, 22:52

    Does Time Run Backward in Other Universes?

    One of the most basic facts of life is that the future looks
    different from the past. But on a grand cosmological scale,
    they may look the same.

    Full article here: