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The Possibility of Paradox-Free Time Travel 421

Posted by kdawson
from the fire-up-the-delorean dept.
relliker writes in with word of a paper up on the ArXiv by Seth Lloyd and co-workers, exploring the possibility that "postselection" effects in non-linear quantum mechanics might allow paradox-free time travel. "Lloyd's time machine gets around [the grandfather paradox] because of the probabilistic nature of quantum mechanics: anything that this time machine allows can also happen with finite probability anyway... Another interesting feature of this machine is that it does not require any of the distortions of spacetime that traditional time machines rely on. In these, the fabric of spacetime has to be ruthlessly twisted in a way that allows the time travel to occur. ... Postselection can only occur if quantum mechanics is nonlinear, something that seems possible in theory but has never been observed in practice. All the evidence so far is that quantum mechanics is linear. In fact some theorists propose that the seemingly impossible things that postselection allows is a kind of proof that quantum mechanics must be linear."
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The Possibility of Paradox-Free Time Travel

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  • Time Cube? (Score:5, Funny)

    by Lythrdskynrd (1823332) on Sunday July 25, 2010 @02:38PM (#33022414)

    http://timecube.com/ [timecube.com] ... obviously.

  • I learned everything about this already from Futurama
    • by khasim (1285) <brandioch.conner@gmail.com> on Sunday July 25, 2010 @02:50PM (#33022518)

      The problem with all of those approaches is that they assume a "meta-time" (even if not stated as such) that will alter the PRESENT based upon changes in the FUTURE.

      That's how a photograph that you have right (taken in the future) now will change based upon events that have not happened yet.

      Once you get past that, you understand that there is no "grandfather paradox". If it exists in the current time then it exists in the current time. The future will not reach back and "clean up" the present to make it more acceptable to the future.

      Obligatory cartoon linkage:
      http://www.smbc-comics.com/ [smbc-comics.com]

      • by Schadrach (1042952) on Sunday July 25, 2010 @03:21PM (#33022752)

        So, what you are suggesting in the case of the grandfather paradox is that you kill your grandfather, are never born, and yet continue to exist unscathed? Essentially being a causeless effect, or rather an effect that causes it's cause never to have occurred?

        Essentially the opposite of a closed temporal loop where something is it's own cause.

        Of course the SMBC leaves out the third possibility: You go back in time and only change things that were unintended, causing you to not notice any changes because they "were always like that" as of the moment you made said changes. But that of course assumes that changing something that would effect you in some way actually does effect you, and not cause you to live without ever being born (for example).

        • by Cylix (55374) * on Sunday July 25, 2010 @03:34PM (#33022864) Homepage Journal

          The post selection method would be...

          You killed the man you thought to be your grand father, but it turns out you are from an illicit relationship. Your grand mother quickly remarries and the man assumed all the roles the other fellow would have done.

          That version of the grand father post selection paradox can go soap opera silly really fast. It would get really strange if everyone you kept killing in your family tree resulted in discovering that each generation was conceived in a series of illicit relationships. Take that days of our lives!

        • Pretty much, yep. (Score:4, Interesting)

          by khasim (1285) <brandioch.conner@gmail.com> on Sunday July 25, 2010 @03:43PM (#33022904)

          Essentially being a causeless effect, or rather an effect that causes it's cause never to have occurred?

          Pretty much, yep. Because you are now existing at a prior point in the chain of causality. So you've already accepted either:
          1. circular causality (and a supreme janitor who cleans up the past to keep the future tidy) (and how would you tell the difference) or

          2. effect without cause (because you exist prior to your parents giving birth to you).

        • by tius (455341) on Sunday July 25, 2010 @06:33PM (#33023990)

          I think the problem is that everyone assumes that time is essential to processes within the universe. There's nothing that I've ever read or studied that suggests reasonably that this assumed correlation is actually real.

          Consider that if time is real, and not fundamental to processes (i.e. the correlation is not causal) then it is entirely possible to travel back in time and kill your grandfather without self destructing. This is because in the stream of processing your existence, all the important stuff has already occurred in the process dimension.

          But looking around this idea it seems more likely to me that time is an illusion as far a real dimension is concerned. It strikes me more as an analog to temperature; i.e. it's a statistical like reference. Do we really experience the passing of time or do we really just have a sense of passing of process?

          How do we measure time? By change in processes. You can pull in relativity and still see that the effects on time are purely due to the real effects on the spacial dimensions. The relative dimensional changes in space lead to changes in the processes used to measure time.

          I'm not sure if this is true, but if it were it eliminates the absurdity of the grandfather paradox.

      • I hate time-travel.

        It will never work, for exactly the reason you brought up--meta-time; that is to say, that more than one time period has to physically exist at any moment in meta-time, and you can "travel through time" by going between these physically-existent worlds. How do you travel through meta-time? Presumably, that's actual time in exactly the same sense as normal time, only it keeps track of what people do in this theoretical framework of moving from one physical, literal world to another copy

        • Re: (Score:3, Informative)

          by Dwonis (52652) *

          And if the past and future already exist, what the hell does energy even mean? No, I say, fuck all that.

          I'm pretty sure that quantum mechanics experiments have taught us that the universe doesn't care what you fuck.

  • One of these quantum universes has to have every quantum event probability = 0%, and one p=100%. Those two together are the paradox of possibility-free time travel. In one, there's no chance of free will. In the other, a time machine is certain.

    • by Artraze (600366)

      The idea of free will v.s paradox free time travel, and really all time travel paradoxes in general, is built upon the notion that the universe is causal. That seems like a pretty basic and safe assumption, but we are making it based how things seem, not direct observations and experiments. If our technology gets to the point where we're manipulating space and time, than we would be in a much better position to know. For now though, all we 'know' is time travel doesn't exist and the universe is causal.

  • But if I'm going BACK in time, I'm taking some aspirin, toothpaste, deodorant, and toilet paper with me. I hope the machine is big enough.

  • Caution about ArXiv (Score:5, Informative)

    by vsage3 (718267) on Sunday July 25, 2010 @02:46PM (#33022482)
    I have neither the capacity nor the will to vet the paper, but it should be noted that ArXiv is not peer reviewed. While experimentalists use it as a place to publish pre-prints of their papers and will typically only put them up after the papers have been accepted, but theorists use the medium as a substitute for publishing and so many wacky and untrue claims get put up there.
    • Re: (Score:2, Informative)

      by Anonymous Coward

      "...many wacky and untrue claims get put up there."

      This is demonstrably untrue. Since the mid-90s ArXiv has been the standard way in which theorists communicate their papers to a wider audience. Although you're technically correct that it's not peer reviewed in the traditional sense, it does have quite a strict authentication and author endorsement procedure that filters out 95% of the garbage that would appear there if it were open to all. In addition, reading a paper's abstract and looking at the names an

      • by martin-boundary (547041) on Sunday July 25, 2010 @04:52PM (#33023368)
        Nonsense. Appeal to authority is one of the standard logical fallacies.

        The problem with this in the case of theoretical papers is that theory, quite often, is complicated. So complicated that there will be bugs in the statements of the proofs, and ambiguities or inaccuracies in the statements of the theorems. These are picked up by peers when they review a paper formally, but usually skipped when they peruse the paper cursorily.

        What's worse, when a paper is coauthored by a well known researcher and one of his students, it's highly likely that the student did all the work and was merely pointed in the right direction by the other. Then the authoritative paper you read on xxx is no better in quality than a paper written by an unknown.

        It's ok to feel that appeal to authority works surprisingly well... if your standards are so low. But some people have higher standards and make a clear distinction between formal peer review and unpublished dissemination.

  • by Joe The Dragon (967727) on Sunday July 25, 2010 @02:49PM (#33022504)

    Time travel leads to Parallel universes that make paradox not happen in the one you left.

  • by greyworld (802114) on Sunday July 25, 2010 @02:49PM (#33022512) Journal
    Am I the only person who has noticed the Authors name? Seth Lloyd = Sith Lord I think we should be very cautious of these findings.
    • by rubycodez (864176)

      and at least one of the others must be watched with caution, as sith lords always appear in pairs.

    • You should be cautious because he's a Mech E. If his CS and physics ideas had any merit, he'd switch departments.

  • Dress it up! (Score:5, Insightful)

    by Beelzebud (1361137) on Sunday July 25, 2010 @02:50PM (#33022520)
    You can dress up pseudoscience with a bunch of equations, but tell me how this is based on any type of actual science. If this is science, then Deepak Chopra must be an actual genius...

    I'm not an expert but it does seem like a lot of physicists are just lost in their own little worlds. I realize science is a process, but spending valuable time "researching" time travel, before we can even explain what time or even gravity is, seems like skipping over the hard work to spend time on "fun stuff".
    • Re: (Score:2, Interesting)

      by maxwell demon (590494)

      I don't think the authors expect to see post-selection time machines any time soon. However such work may enable us to understand better the structure of quantum mechanics. By exploring what is and isn't possible in theory, we get guidelines in which directions it makes sense to look for adaptions of quantum theory (e.g. for quantum gravity), and which directions are better avoided.

      • by Artraze (600366)

        Exactly.

        From TFS:
        >In fact some theorists propose that the seemingly impossible things that postselection allows
        >is a kind of proof that quantum mechanics must be linear.

        Work like this is not meant to be practical; it's a thought exercise. It provides a sort of preview of different things that may or may not be possible, and can inspire other scientists. For example (given the above context), it may generate a testable idea which can then be used to disprove non-linear quantum mechanics.

      • by impaledsunset (1337701) on Sunday July 25, 2010 @04:20PM (#33023142)

        I'm completely with the parent.

        While I don't think that you can call pseudoscience the exploration of the implications of a theory that are unlikely to be possible in practice, let's assume it's pseudoscience. So what? It was pretty interesting read, at worst it will serve as an inspiration to some science fiction author. It's interesting. You know why? Because it is "fun stuff"! Also, as the parent stated, exploring the theoretical possibilities provides better understanding of the model, allows you to improve the model and might allow you to find the boundaries where the model stops being correct. Also, making advances in the part that don't apply in practise might improve the understanding of the practical part of the model. Infinitesimals don't seem to exist in our universe, but the models that explore their properties closely have been the basis for most of the physics.

        Also, I might not understand the article completely, but it, along with another report that was posted to Slashdot less than an year ago, seems to show a method of time "travel" that doesn't allow to send information back in time at all. Seems reasonable, and not against anything that I know about the world I'm living in. It would completely blow out my idea of time -- I'm a firm believer that only the current moment exists, and you can't affect or travel to previous ones, and that other interpretations of time are merely implementation details of the physical models we use -- but these results wouldn't be against any physics I know. Also, even if there is an experiment that confirms that this paper isn't bullshit, and it is empirically proven that this kind of time "travel" is possible, the results won't have a single interpretation. I wouldn't be surprised even if someone builds another model that doesn't involve any time travel that explains the same empirical results.

        Yes, someone needs to verify the premises and the conclusions, I don't have good enough knowledge to do that myself on the first read, but I didn't see any mistakes pointed out by the GP, only baseless claims, so I'd rather go with the article and/or the paper. I have a direct question for the GP: We have no idea what time is, OK. Suppose that our current theoretical model allows for time travel (which would seem to be the case unless the article is full of mistakes). Are you denying that testing them would allow us to be closer to understanding what time is?

    • Re:Dress it up! (Score:5, Insightful)

      by Lifyre (960576) on Sunday July 25, 2010 @03:16PM (#33022726)

      Having been part of the physics community for a few years (got a BS in it for some reason) I can say those little worlds often result in some useful science. Usually when someone not in the fantasy land looks in sees that one or two things that guy is working on might have merit and looks into it. Who knows if one of these guys working on time travel might actually figure out what time is? If we don't know what time or gravity even is who is to say that this work might not be instrumental in figuring it out? As long as it is a minority working on the fantastical, science will still make progress with a few boosts here and there by some crazy idea that actually works.

  • Primer (Score:5, Interesting)

    by kylben (1008989) on Sunday July 25, 2010 @03:01PM (#33022614) Homepage
    The movie "Primer" had an interesting take on avoiding paradoxes. http://video.google.com/videoplay?docid=3909854615539675694# [google.com] (entire movie online)
    • by swb (14022)

      That was a great movie, but difficult to keep track of the time travel.

      I don't think they ended up with specific paradoxes, but I seem to recall a lot of attempts to fix things by going further and further back; perhaps not explicit paradoxes, but a lot of manipulation of the past to try to impact the future.

    • The main thing I learned about time travel from Primer is that it leads to headaches when it gets involved. I'm really hoping I'll never be one of the people who are supposed to comprehend what's happening should we invent it.

      • by kylben (1008989)
        I stopped trying to keep track halfway through and just focused on the universal human drama of having to decide whether to kill the guy that died in your kitchen next Tuesday.
      • by AJWM (19027)

        I'm really hoping I'll never be one of the people who are supposed to comprehend what's happening should we invent it.

        Yeah, especially considering that the movie wasn't an advanced course, but only a ... wait for it ... Primer.

  • Or... (Score:2, Insightful)

    by haystor (102186)

    Or, we go with the simple, elegant solution to the problem...it's not possible.

  • Did he prove that paradox-free time travel is possible thanks to possibility that quantum selection is non-linear, or did he prove by contradiction that quantum selection is linear?

    • Re: (Score:2, Informative)

      by maxwell demon (590494)

      Neither. Assuming he's right (and the Technology Review article correctly reproduced his claims; I haven't actually read the arXive article yet), he proved that you cannot have non-linear quantum mechanics without time travel. Given that some people try to resolve the measurement problem by adding nonlinearities, that's certainly an interesting result.

    • Re:the other angle (Score:4, Interesting)

      by icannotthinkofaname (1480543) on Sunday July 25, 2010 @04:08PM (#33023052) Journal

      I think it's the first one, but only because I'm pretty sure it can be rephrased thus:

      "He proved that paradox-free time travel is possible through postselection of quantum teleportation by postselecting the condition that quantum mechanics is non-linear."

      However, I believe this phrasing assumes that the probability of quantum mechanics being non-linear is nonzero, so if I just divided by zero, I apologize.

  • by fahrbot-bot (874524) on Sunday July 25, 2010 @03:07PM (#33022656)

    ...anything that this time machine allows can also happen with finite probability anyway.

    Now, if we can just hook in the logic circuits of a Bambleweeny 57 Sub-Meson Brain to an atomic vector plotter suspended in a strong Brownian Motion producer (say a nice hot cup of tea)...

  • Well you lost me right after 'the grandfather paradox'. I even read the article and I *still* don't understand. Is there a summary for dummies ?
    • Re: (Score:3, Informative)

      by CODiNE (27417)

      Grandfather paradox: Go back in time, shoot your grandfather... now your father wasn't born, you weren't born. Which means your grandfather doesn't get shot, so you get to be born, etc... the universe flip-flops your time travel forever, the record is skipping for eternity.

      I personally like Primer and it's time machine concept. You could go back to yesterday and kill yourself, that version of you would die but you would not disappear. Also if you kept the yesterday you from going in the time machine yo

      • by lbalbalba (526209)
        Yeah, thanks... I got the 'grandfather paradox', and even the concept of the fact that you doing something in the past will not retro-actively change the future as well (paradox free time travel). I just failed on all the 'quantum mechanics' and 'postselection' etc. stuff... That is, I understand the concepts that make this work, just not the individual mechanisms that make up the solution.
      • by JWSmythe (446288)

        Unless destiny says that specific important events can and will happen without fail. Those who shape the future will always exist, and those who don't ... well ... don't really matter.

        Obviously if you went back in time and killed your grandfather, that would show that you did exist. So in killing your grandfather, your creation simply came through a different path than you remembered. A simplified explanation would be, you go to McDonalds to get a hamburger. There are peopl

  • Other issues exist (Score:4, Interesting)

    by AnAdventurer (1548515) on Sunday July 25, 2010 @03:14PM (#33022704)
    And if you travel outside of your light-cone? (other then math breaking down)
  • by Tablizer (95088) on Sunday July 25, 2010 @03:23PM (#33022768) Homepage Journal

    Quantum mechanics is a big tease. It seems whenever it's about to give you Jetsons or Stargate technology, there's always a big fucking loophole or caveat. You can go into the past, but you can't come back and/or die; you can travel faster than light, but the universe will end before you reach your destination; you can predict the future, but will change it in the process without knowing what the change is; you can date 3-breasted aliens, but they all have penises, or whatever. (Okay, I made up the last one.)

    There must be a God, because nature wouldn't find a way to tease us with so many Almost's and fuck with our minds in so many different ways that QM does.

    Or maybe it's the anthropic principle keeping us from destroying the universe with time weapons?

    Something odd is going on. Time for a congressional investigation.

    • by Gorobei (127755)

      Sheesh, you get semiconductors, lasers, quantum bomb detectors and god knows what else, and you want a stargate right now?

      • by JWSmythe (446288)

            Want a stargate? I already have one. My grandfather found it in the desert in Egypt years ago. I can turn it on, but I haven't found a combination of these freakin' buttons to do anything useful.

  • by bar-agent (698856) on Sunday July 25, 2010 @03:23PM (#33022772)

    As far as I can tell, the article is saying that if you impose a condition in the present, you cause the past to change so that it matches. This process of imposing a condition must affect the quantum mechanical properties of whatever you are checking, similar to a quantum computer.

    So basically, if your granddad rigs up a machine that kills him depending on the quantum state of a particle, and then he leaves that particle in an indeterminate quantum state until he has your dad and your dad has you, and then you collapse that particle's waveform into the state that would have killed him, he will have died back then. And somehow paradox is avoided.

    Wha?

    • by TubeSteak (669689)

      So basically, if your granddad rigs up a machine that kills him depending on the quantum state of a particle, and then he leaves that particle in an indeterminate quantum state until he has your dad and your dad has you, and then you collapse that particle's waveform into the state that would have killed him, he will have died back then. And somehow paradox is avoided.

      Schrödinger's Granddad?

      It's like allowing the cat to have kittens and letting them out of the box with quantum guns strapped to their heads.
      On second thought, this could make a great movie.

  • idea of time travel (Score:4, Interesting)

    by phantomfive (622387) on Sunday July 25, 2010 @03:34PM (#33022860) Journal
    I can accept FTL travel as maybe possible, but time travel seems farfetched to me. It means that every single state that the universe has ever been in is preserved (somewhere) in it's exact state. We're not talking about the awareness of the state being preserved on the speed-of-light boundary away from the location of the state, it's the actual state, in a way that can be modified and changed. Does this even seem reasonable? How could all that be stored?

    Not only that, it means that a change in one of those states will instantly change every subsequent state. So when you travel back, everything will be different. This is really hard to believe.
    • Re: (Score:2, Informative)

      by maxwell demon (590494)

      I can accept FTL travel as maybe possible, but time travel seems farfetched to me.

      You can't have one without the other.

      • Why? By current physics, you can't have either. FTL travel could possibly come up in the future as we come to a better understanding of physics. My argument was that we will never come to time travel, no matter how our understanding of physics changes.
    • Re: (Score:3, Interesting)

      >Does this even seem reasonable? How could all that be stored?

      Yep. People who believe in parallel universes don't seem to comprehend the vast amount of data that would need to be stored to make such a thing possible. Every electron twitch - boom, new universe, with all of its state intact, loaded into a new memory location far away from the previous one.

      I guess with time travel they are saying all the previous states are still stored. Pretty close to the same thing. You would need a whole other unive

      • by agrif (960591)

        Yep. People who believe in parallel universes don't seem to comprehend the vast amount of data that would need to be stored to make such a thing possible. Every electron twitch - boom, new universe, with all of its state intact, loaded into a new memory location far away from the previous one.

        Maybe the universe is just a gigantic collection of patchsets. Or, if you're familiar with git, that's a better analogy because the source is less rigidly hierarchical than standard VCS. Or...

        If you've ever used the amb operator in Lisp or any other language, think of every quantum event as a variable defined by the amb operator. It's not well defined until you ask it, specifically, what it is.

        Or, if you're not into amb, think of the universe as a deep tree search of all possible combinations of events, whi

      • by PagosaSam (884523) on Sunday July 25, 2010 @07:30PM (#33024278)
        You know, that a funny thing about infinities. You have room for everything. ;-)
    • Re: (Score:3, Informative)

      by JohnFluxx (413620)

      There seem to be a few misconceptions from the people that have replied.

      If we take "FTL" to strictly mean travelling faster than light travelling nearby, then in any macroscopic ordinary sense special relativity doesn't let you do this. There are a few exceptions - for example if the curvature of space is such that it can no longer be considered flat, such as near extreme black holes. Or for extremely short periods of time.

      But often this definition is too strict, and "FTL" proponents would be happy with a

      • Re: (Score:3, Interesting)

        by blincoln (592401)

        But often this definition is too strict, and "FTL" proponents would be happy with arriving someone else faster than it would take light to travel that same journey, without getting caught up in the details of whether you were actually travelling faster than light at any point. There are various possible loopholes - teleportation, moving space itself, using a "hyperspace" to travel in, and so on.

        Assuming that the theory of relativity is more or less accurate (specifically regarding the ability of observers m

  • Fact (Score:5, Funny)

    by Charliemopps (1157495) on Sunday July 25, 2010 @03:46PM (#33022920)
    “The Encyclopedia Galactica has much to say on the theory and practice of time travel, most of which is incomprehensible to anyone who hasn’t spent at least four lifetimes studying advanced hypermathematics, and since it was impossible to do this before time travel was invented, there is a certain amount of confusion as to how the idea was arrived at in the first place. One rationalization of this problem states that time travel was, by its very nature, discovered simultaneously at all periods of history, but this is clearly bunk. The trouble is that a lot of history is now quite clearly bunk as well.”
  • The concept of a paradox is entirely a human concept - in other words, it's in the eye of the observer. The universe wouldn't "classify" you going back in time and killing your great-grandparents before you were born as a paradox, simply because the universe is not an observer. It would happen - so what - "It is what it is". That would just be part and parcel of the way the universe works in that particular case.

    Attempting to say that this would result in a paradox as far as the universe is concerned is anthropomorphizing the universe to an absolutely unforgivable degree. Sure, it makes for a good time travel story, but the universe won't lose any sleep over it, any more than it does for me writing "The next phrase is false." "The previous phrase is true." "Both the previous phrases are true" "The previous phrase is true" There's no paradox. The universe doesn't suddenly go wonky, and cats mate with dogs, etc.

    • Re: (Score:2, Insightful)

      by maxwell demon (590494)

      While the concept of a paradox is indeed about our language and logic, the point is that theories about the universe are also just in our language and logic. The point is that it's possible to say nonsense, and sometimes such nonsense shows up by the statement (or collection of statements) being paradox. So basically time travel paradoxes mean that any description of the universe which involve classical causality and time travel are internally inconsistent, and therefore cannot be used to describe the real

    • There's no paradox. The universe doesn't suddenly go wonky, and cats mate with dogs, etc.

      Believe me, I really wanted to mod you up until this point, but there's an assumption here that needs to debunked. [youtube.com]

  • Quantum Leap (Score:2, Informative)

    Clearly no one has watched Quantum Leap. You can only time travel within your own life. Time travel is so far off that we won't see anyone traveling back in time yet.
  • by koolfy (1213316) <koolfyNO@SPAMgmail.com> on Sunday July 25, 2010 @04:16PM (#33023112) Homepage Journal

    it does not require any of the distortions of spacetime that traditional time machines rely on.

    Wait, did I missed the part where time machines were something traditional or common or anything like that ?

    Seriously, time travel became mainstream and nobody told me ?

  • If (Score:3, Insightful)

    by Dunbal (464142) * on Sunday July 25, 2010 @04:24PM (#33023172)

    If time travel existed at some point in the future, we would have had evidence of its existence in the past...

    • Re: (Score:2, Insightful)

      by maxwell demon (590494)

      Only if time travel allows you to go back into the past arbitrarily far.

      • by Dunbal (464142) *

        True. Then time travel would be spotted "n" years before it is "discovered", "n" being your non-arbitrary number.

    • by JWSmythe (446288)

      Exactly what kind of evidence would you expect?

      If someone went back 20,000 years, and dropped their very nice pen from 1,000 years in our future, wouldn't you expect that the pen may have decomposed by now?

      Or.. it's still laying out there, and no one has done an archeological dig yet at that specific geographic point to find it.

      Or... as humans tend to do, someone found it and destroyed it because they didn't understand it.

      • by Dunbal (464142) *

        I would expect time travel to exist at every point in time, since theoretically a person/persons capable of time travel would eventually visit pretty much every year for whatever reason (if only to avoid bumping into themselves). Remember that they have the whole future ahead of them, so lots of trips to different times in the past can be scheduled. If a future WITH time travel exists, then essentially time travel must appear simultaneously across the entire past, even if the future people are visiting diff

  • Was Seth Lloyd perhaps inspired to design paradox-free time machines by the great Christopher Lloyd?

  • Knowing (not predicting, not hinting, but knowing) our future is, from the future perspective, altering the past. That means that physic proved that we won't be able ever to know for sure our future?

    Well, is not so bad, at least we won't go extinct because of blue butterflies.
  • John Titor (Score:4, Funny)

    by ModernGeek (601932) on Sunday July 25, 2010 @04:43PM (#33023304) Homepage
    John Titor
  • I always liked the notion that even if I went back in time and tried to kill my grandfather, I would never succeed, because obviously I didn't kill him.

    Of course, there's no great correlation between my liking something and it being physically true. Not yet, anyway.

  • I thought on some current thinking there is no such thing as "time"; like money, it is just a representation of something more fundamental - change in entropy perhaps. Things in the Universe change, and we assign a scale to the perceived rate of change by comparing it to something else that changes in what we consider to be a regular way. Like money, the value of time varies according to where it is being used or measured.

    If this view or something like it is correct, then "time travel" is a bogus concept. (

  • The seemingly impossible things that relativity allows is a kind of proof that Newton is right and Einstein is wrong. We'll all laugh at him after light isn't bent around the eclipse.

    FTFY

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