Time Travel?

Discussion in 'Pseudoscience' started by the legendary shark, Mar 5, 2016.

  1. the legendary shark Registered Member

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    Hello, everyone.

    As this is my first post on this forum, I thought I'd first type a little about myself to add some context.

    I am not a scientist or academic in any significant sense. In fact, I am a simple, 50 year old, truck driver who was recently made homeless. I have always, however, been fascinated by cosmology and astrophysics although my understanding is shallow. When driving, instead of listening to mindless radio I enjoy listening to podcasts and lectures and it was whilst listening to one of these (TGC's Impossible - Physics Beyond the Edge, I think) that the following idea occurred to me.

    I do not even dignify the following with the description of "hypothesis" because it is simply an idea that crossed my mind as I was listening. I know that my knowledge, and therefore my understanding, is poor and so I do not present this idea as "something I've worked out" or even as something demanding serious scientific consideration. I am fully aware of the fact that this thought is based upon an incomplete understanding of the topic and may not, given the depth of scientific knowledge and thought already extant, and the billions of minds on the planet, even be an original idea. Indeed, I don't even fully understand this idea myself so I hope you'll forgive me - and educate me - for the misconceptions and errors it contains.

    Thank you for your indulgence.

    Time travel, as far as I understand it, is not specifically "outlawed" by current understanding but does seem to be highly unlikely due to the potential paradoxes inherant to such an idea. Leaving aside the "Many Time-Lines/Universes" hypothesis, I wondered if time travel might be possible in this universe.

    Let us imagine a time-telegraph - an instrument capable of sending a single particle back through time. Current thinking is that, if a particle is sent back through time from Wednesday to Tuesday, a paradox may be constructed. The receiver on Tuesday detects the particle from the future (Wednesday) and must answer a question based on the received particle, for example, is the particle positively or negatively charged? If the equipment receives a positively charged particle and the scientist reports it as negatively charged, then a negatively charged particle would be sent back from Wednesday. This means a negatively charged particle could be sent back from Wednesday to Tuesday, where it would be received and misreported as a positively charged particle, therefore a positively charged particle would be sent back and so on, creating a paradox. (The charge could be used as a yes/no answer to a question, for example.) Sorry if that's not very clear.

    However, this is what occurred to me. In the time between Tuesday and Wednesday, everything has moved. The equipment (and let's imagine that the transmitter and receiver are the same instrument) is on a planet which is spinning and orbiting a star which is itself orbiting the galactic centre, the galaxy is also moving and the universe is also expanding. Therefore the chance of calculating all this motion so that the particle ends up finding the correct point in spacetime might be very difficult to calculate with sufficient accuracy - but not impossible. However, if a particle was sent back from Wednesday to Tuesday on the correct vector, that particle must, at the point of transmission, have to pass through itself (assumption), to briefly occupy the same point in spacetime.

    My idea was that the particle cannot do this (assumption) and so would be somehow perturbed from its course by atomic charges or forces. Given the change of vector, and the motion of the equipment in expanding spacetime, might this mean that the particle would travel from Wednesday to Tuesday but emerge at least one light day away from the receiver? A particle sent back one second might "emerge" at least one light second away from the receiver - or miss the receiver by the same distance. This would make time travel possible without the danger of causing a paradox. Unfortunately for science fiction authors, this would mean that if a temporanaut was sent back 65 million years to study the dinosaurs, he or she would emerge at least 65 million light years from the earth. The information sent back in time would be too distant to impact past information and therefore be incapable of affecting it in any way. Indeed, without a receiver, the particle travelling back in time might never "emerge" and continue its course right back to the Big Bang (assumption).

    This idea might be tested by constructing a seperate time telegraph and receiver one light second apart and sending a particle back in time by one second. The receiver, upon receiving the particle, signals the transmitter. Given perfect timing and equipment, the transmitter would only know if the experiment had been successful at the same instant the particle is "sent back," if that makes any sense. Given the slight delays caused by real-world equipment, however, the transmitter would probably only know if the experiment was successful after transmission. Again - time travel without the paradox.

    Thank you for your indulgence, I hope this post made some kind of sense and look forward to your comments. (I'd also like to know which fields of mathematics I should study in order to try and figure this out properly - if it's a viable idea which, of course, I'm not sure it is.)
     
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  3. paddoboy Valued Senior Member

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    Time travel in its simplest form and as allowed and predicted by GR, is people in different frames of references, where time in one frame is passing slower than time in another frame, and that this person returns to the original frame. eg: If you and I were twins, and I set off at 99.999% light speed for 6 months, returned in another 6 months later, so that by my own biological and on board clocks, 12 months have passed, I would be returning to an Earth 230 odd years into my future, with you long dead and buried.
     
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  5. DaveC426913 Valued Senior Member

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    This similar problem has occurred to me (and I'm sure, others).

    All time travel stories make the implicit assumption that the target (in the past) is geographically located in the same place as the sender's location. Or, if not the same spot, the target is selected as a location that is calibrated with respect to the sender's location.

    To me, this is a huge hand-waving assumption, made for the sake of a story, because it is an essentially intractable problem.

    How does a time machine travel (or merely see) through time, yet tie itself to some basement laboratory sending location that does not even exist in the past? Does it have an anchor to some fluffy laylines in the Earth or what? If it goes back 65 million years, does it account for tectonic shift?

    It can't be a matter of taking into account the motions of Earth, Sun and Milky Way, since that would require some absolute frame of reference, which is expressly forbidden by relativity.

    This, to me, is one of the things that prohibits the possibility of time travel even in principle.
     
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  7. DaveC426913 Valued Senior Member

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    I lie. There is one way that time travel could make a connection, not just through time, but also through space.

    If the receiver were built first, in some specific location, and it managed to broadcast its location forward in time. The sending time travel device/vehicle could travel only as far back in time as that receiver, and could be used to calibrate the location of the arrival from the future.

    Too bad that means that we can never travel into our own past, not until someone builds a receiver.

    H.G. Wells' Time Traveller (who is never named) would have had to build a receiver in his lab, and turn it on before getting in his machine. He could go forward and come back, but he could never travel back farther than the point where he turned on the signal.
     
  8. the legendary shark Registered Member

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    11
    Thanks for your replies.

    I was actually thinking about a way that time travel (by which I mean sending a particle or information specifically back through spacetime, ie., contrary to the "arrow of time") might be theoretically possible without causing a paradox. I have no idea about the mechanics of doing this - I'm not certain anybody does - and that aspect I've not attempted to investigate. I perhaps should not have mentioned temporanauts and traveling back to study dinosaurs because this might have given the wrong impression. My thought was primarily concerned with natural conditions and/or effects that might allow for time travel whilst at the same time disallowing paradoxes.
     
  9. DaveC426913 Valued Senior Member

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    Tachyons are hypothetical particles that travel faster than c. They are not forbidden by relativity.
     
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  10. the legendary shark Registered Member

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    True, but even if they do exist I don't think they can be used to carry information. As far as I understand it, it's information that causes paradoxes. (I love the idea that as tachyons lose energy, they increase in speed!)
     
  11. DaveC426913 Valued Senior Member

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    Well, that will go for any set up you think of that allows travel into the past. To move forward with your idea you must first abandon that assertion, then find a means to do the traveling.
     
  12. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    Time travel is impossible, for the simple reason that only an evolving present exists. Yes there is a past that did exist and a future that will exist.

    True by traveling very fast in a round trip from Earth and back to Earth your body may have aged only 30 years while your twin brother who stayed on earth has aged 90 years. This could also happen with no need to leave earth by going into suspended animation for 60 years at age 30. Neither is time traveling - only slowing your net rate of aging. Neither is possible now, but suspended animation seems to be much less expensive and is done now for embrios.

    Yes there are many paradoxes the rule out true time travel, but none are needed to show it is impossible. You can neither go back and watch yourself blow out the candles on your 10 years old birthday cake; Nor go into the future to watch your body being buried. The first of these events did occur and the second has yet to occur, but neither exists now "some where in space time" for you to visit. Only the evolving "now" exists in space time.
     
    Last edited: Mar 6, 2016
  13. C C Consular Corps - "the backbone of diplomacy" Valued Senior Member

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    Media speculation is jumping the gun. The pregeometry related movements and their overthrow of the primacy of causality, space, and time will take years of experiments to bear the fruit necessary to brush away the old school. Philip Walther's team only took a tentative step last year with their test, demonstrating an ambiguous mix or garbling of past (cause) / future (effect). Caslav Brukner's group just recently got a 63,000 dollar grant from FQXi to help boost their research. Plus, these particular endeavors are only conservatively looking forward to items like better quantum computers. Not a distant prospect of even the possibility of mitigated time travel at the microscopic scale or particle level.

    Brukner & colleagues: http://www.nature.com/ncomms/journal/v3/n10/full/ncomms2076.html

    Walther & the rest's experiment: . . . Thus we can take the interference in our experiment to demonstrate that the two events cannot be ordered according to any definite causal relation; in this sense, our experiment can be seen as the first realization of a ‘superposition of causal orders’. Indeed, it is shown elsewhere that the 2-SWITCH realized here corresponds to an example of a causally non-separable process, as defined in ref. 5.

    In conclusion, we have shown how to use additional degrees of freedom of the physical system encoding a quantum system to apply quantum operations without a fixed, definite causal order. This allowed us to accomplish a task which is impossible with a fixed order of operations. Our demonstration of superimposed quantum circuits illustrates that removing the requirement of a fixed-gate order can provide quantum algorithms with real practical advantages and it shows a feasible way to obtain this advantage.
    http://www.nature.com/ncomms/2015/150807/ncomms8913/full/ncomms8913.html
     
  14. paddoboy Valued Senior Member

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    21,703
    As we have discussed before, that is debatable at worst.
    Time travel is allowed for by GR, and many reputable physicists and opinions are open on that score: Difficult? Beyond our means at present? Yes certainly, but not impossible according to our knowledge at this time..

    GR tells us that all frames of references are as valid as each other: The bloke travelling round the Earth very fast, whose clocks tick at one second per second until he reaches 30 years of age both mechanically and biologically. Nothing fake, it is real and his time as far as he is concerned does not slow down.
    The bloke left on Earth also in his frame sees time pass at one second per second until he has aged a realistic and true 90 years.
    When the traveller is reunited on Earth, his 30 years of aging are as real as the stay at home's 90 years of aging and an Earth 60 years into his future.
    Anyone in suspended animation has his body clock stopped, while mechanical time keeps ticking. There is no time dilation as such.
    This is also the general view of many reputable physicists.
     
  15. krash661 [MK6] transitioning scifi to reality Valued Senior Member

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    every single one of these time travel topics--across the world--are very ridiculous and comical--every single one, no matter whom or what(including popular mainstream scientist).
    in the past(on here and other sites), i have mentioned exactly why.
     
  16. krash661 [MK6] transitioning scifi to reality Valued Senior Member

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    the physical state of an entity aspect is not the issue. the actual issue is simply the consciousness aspect. also keep in mind-- " a system -to-a-system"
     
  17. DaveC426913 Valued Senior Member

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    No, you haven't.
     
  18. DaveC426913 Valued Senior Member

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    It is not impossible in principle. There are GR solutions (granted, exotic ones) that allow the traveling backward in time. They don't require hypothetical negative energy or exotic matter, they "simply" require a black hole of a particular shape.

    What happens is, near the BH (but outside the EH), the space-time axes get rotated by 90 degrees, so that when one travels in what was one of the spatial directions, they are actually now traveling along the timelike dimension. Peel off after a while and you'll find yourself in the past or future, depending on which way you turn.

    I'll see if I can find a reference.
     
    Last edited: Mar 7, 2016
  19. DaveC426913 Valued Senior Member

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    This is a tautological (fallacious) argument. You claim time travel is impossible and cite that the reason for that is that we cannot travel to the past or future.
     
  20. krash661 [MK6] transitioning scifi to reality Valued Senior Member

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    you must be new here. maybe check before you tell me i have not.
     
  21. DaveC426913 Valued Senior Member

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    #12 is your first post in this thread.

    If you wish to make your point here in this thread, you should do so.

    I have pointed out elsewhere that I am King of all Creation. I don't need to rehash that here, you'll it have to accept that it's true for the duration of this thread.

    Please Register or Log in to view the hidden image!

     
  22. krash661 [MK6] transitioning scifi to reality Valued Senior Member

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    it appears you simply cannot grasp this piece of that sentence that you quoted--which is: " in the past(on here and other sites),
    is that so? except i rather sit here and read the ridiculous shiit you are saying instead of typing a bunch of more shiit that then after i have typed it all out, you will come back with more ridiculous nonsense and tell me that i am wrong. again, i will only help the ones i see fit for me to do so..
     
  23. DaveC426913 Valued Senior Member

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    I see the problem; it was due to your punctuation. Sentences normally start with a capital. Mia Culpa.

    Ah. You are a school child. If I'd known that, I would have used language fit for the playground. Again, Mia Culpa.
     

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