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Thread: Are Time Loops Possible?

  1. #1 Are Time Loops Possible? 
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    I'm new to physics and I was wondering if this sci-fi/fantasy plot device that appears in Groundhog Day possible?


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    KJW
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    Quote Originally Posted by MegaDestructor View Post
    I'm new to physics and I was wondering if this sci-fi/fantasy plot device that appears in Groundhog Day possible?
    Nobody knows for sure. They have neither been encountered nor unequivocally excluded. General relativity admits them, but general relativity is not the whole of physics. There may be other physical laws outside the scope of general relativity that excludes them. It would seem that time-like loops violate the second law of thermodynamics, and on this basis, I think they are impossible.


    There are no paradoxes in relativity, just people's misunderstandings of it.
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    Quote Originally Posted by KJW View Post
    Quote Originally Posted by MegaDestructor View Post
    I'm new to physics and I was wondering if this sci-fi/fantasy plot device that appears in Groundhog Day possible?
    Nobody knows for sure. They have neither been encountered nor unequivocally excluded. General relativity admits them, but general relativity is not the whole of physics. There may be other physical laws outside the scope of general relativity that excludes them. It would seem that time-like loops violate the second law of thermodynamics, and on this basis, I think they are impossible.
    What about that endlessly repeating/moving crystal that was in the Scientific news a couple of months back?

    If you didn't pay attention to it at the time I will get you the reference .Did that bear any comparison at all to the OP's question?

    https://www.sciencedaily.com/release...0308131228.htm

    It certainly seemed mind boggling but my mind is easily boggled and the physics of that would be a foreign country to me...
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    Interesting concept, repeating nonstable crystalline structures that keep changing orientation. Could computers use this like they use RAM?
    Growing up, i marveled at star-trek's science, and ignored the perfect society. Now, i try to ignore their science, and marvel at the society.

    Imagine, being able to create matter out of thin air, and not coming up with using drones for boarding hostile ships. Or using drones to defend your own ship. Heck, using drones to block energy attacks, counterattack or for surveillance. Unless, of course, they are nano-machines in your blood, which is a billion times more complex..
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    I think (from hazy memory) that , whilst reproducible any application is very far in the future.

    From what you said I am guessing there is no "Groundhog" state in the configuration to which it returns.

    Are there an infinite amount of configurations?
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    Quote Originally Posted by geordief View Post
    What about that endlessly repeating/moving crystal that was in the Scientific news a couple of months back?
    It's not clear to me what aspect of time crystals you consider to be pertinent to what I said. Oscillatory motion is not new and doesn't indicate closed time-loops because the repeating regions of space are limited and connected to regions of space that are not repeating and advancing in a definitely forward time direction. That is, each subsequent repetition is at a different time to previous repetitions in spite of the cyclic nature of the time crystal. It is worth noting that in principle, time crystals differ from ordinary crystals by having a lower time-translation symmetry, not a higher time-translation symmetry. That is, whereas ordinary crystals have a continuous time-translation symmetry, this symmetry is broken in time crystals to a mere discrete symmetry.

    Time crystals do not violate the second law of thermodynamics because: (1) they are driven by laser pulses, and (2) they are small systems governed by quantum mechanics rather than classical mechanics.
    There are no paradoxes in relativity, just people's misunderstandings of it.
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    Quote Originally Posted by KJW View Post
    Quote Originally Posted by geordief View Post
    What about that endlessly repeating/moving crystal that was in the Scientific news a couple of months back?
    It's not clear to me what aspect of time crystals you consider to be pertinent to what I said. Oscillatory motion is not new and doesn't indicate closed time-loops because the repeating regions of space are limited and connected to regions of space that are not repeating and advancing in a definitely forward time direction. That is, each subsequent repetition is at a different time to previous repetitions in spite of the cyclic nature of the time crystal. It is worth noting that in principle, time crystals differ from ordinary crystals by having a lower time-translation symmetry, not a higher time-translation symmetry. That is, whereas ordinary crystals have a continuous time-translation symmetry, this symmetry is broken in time crystals to a mere discrete symmetry.

    Time crystals do not violate the second law of thermodynamics because: (1) they are driven by laser pulses, and (2) they are small systems governed by quantum mechanics rather than classical mechanics.
    Sure,I just thought I'd run it past you. I had zero real input beyond idle curiosity.
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    It is worth noting that if in some frame-of-reference, the entire space at t1 is identical to the entire space at t0, t1 > t0, then after t1, the spacetime will be indistinguishable from the spacetime formed by excising the region from t0 to t1 from the spacetime and joining t1 to t0. This is because after t1, everything that occurred between t0 and t1 will be completely forgotten. It will be as if this region never existed.
    There are no paradoxes in relativity, just people's misunderstandings of it.
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    As KJW has pointed out, there is an aspect of Physics that suppose the possibility of time loops and many other time related absurdities, but not every aspect of physics do so. Mainly General relativity and Special relativity champion this, but time is still some sort of a puzzle to physicists, hence it is hard to conclude with the current knowledge we have.

    However, the second law of thermodynamics says entropy will always increase for an isolated system, or at most stay constant, which is in conflict with the concepts of time loops.

    Furthermore, it is pertinent to note that the so called arrow of time is caused by the low entropy state at the beginning of the universe which in-turn causes several physical arrows, such as arrow of time, psychological arrow of time, cosmological arrow of time, etc... By careful study one realizes that it is the second law of thermodynamics that makes it impossible for water to flow up the hill, for an egg to make an omelet and for us to grow old, despite the laws of physics saying the reverse of all this is possible.

    What is the second law that casts a dimming shadow on the expectation of physics? perhaps it can impend such time loops and some time absurdities as well. But we must keep our fingers cross as we learn more about spacetime and energy.
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    As KJW has pointed out, there is an aspect of Physics that suppose the possibility of time loops and many other time related absurdities, but not every aspect of physics do so. Mainly General relativity and Special relativity champion this, but time is still some sort of a puzzle to physicists, hence it is hard to conclude with the current knowledge we have.

    However, the second law of thermodynamics says entropy will always increase for an isolated system, or at most stay constant, which is in conflict with the concepts of time loops.

    Furthermore, it is pertinent to note that the so called arrow of time is caused by the low entropy state at the beginning of the universe which in-turn causes several physical arrows, such as arrow of time, psychological arrow of time, cosmological arrow of time, etc... By careful study one realizes that it is the second law of thermodynamics that makes it impossible for water to flow up the hill, for an egg to make an omelet and for us to grow old, despite the laws of physics saying the reverse of all this is possible.

    What is the second law that casts a dimming shadow on the expectation of physics? perhaps it can impend such time loops and some time absurdities as well. But we must keep our fingers cross as we learn more about spacetime and energy.
    "I am sorry for making this letter longer than usual.I actually lacked the time to make it shorter."###
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    Quote Originally Posted by merumario View Post
    As KJW has pointed out, there is an aspect of Physics that suppose the possibility of time loops and many other time related absurdities, but not every aspect of physics do so. Mainly General relativity and Special relativity champion this, but time is still some sort of a puzzle to physicists, hence it is hard to conclude with the current knowledge we have.

    However, the second law of thermodynamics says entropy will always increase for an isolated system, or at most stay constant, which is in conflict with the concepts of time loops.

    Furthermore, it is pertinent to note that the so called arrow of time is caused by the low entropy state at the beginning of the universe which in-turn causes several physical arrows, such as arrow of time, psychological arrow of time, cosmological arrow of time, etc... By careful study one realizes that it is the second law of thermodynamics that makes it impossible for water to flow up the hill, for an egg to make an omelet and for us to grow old, despite the laws of physics saying the reverse of all this is possible.

    What is the second law that casts a dimming shadow on the expectation of physics? perhaps it can impend such time loops and some time absurdities as well. But we must keep our fingers cross as we learn more about spacetime and energy.
    Because we are talking about time loops I can forgive that double post. :-)
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    Nope!!! Everything goes by the Laws of Physics until now ! May be in future its possible !! I think we will be long dead before it happens !
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    Quote Originally Posted by Aslam View Post
    Nope!!! Everything goes by the Laws of Physics until now ! May be in future its possible !! I think we will be long dead before it happens !
    De Ja Vu is the nearest I think we can ever get to it.
    Same with going back in time.
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    Quote Originally Posted by Aslam View Post
    Nope!!! Everything goes by the Laws of Physics until now ! May be in future its possible !! I think we will be long dead before it happens !
    Not at all. If it turns out that causality can be violated, please come and let me know last week? Thank you.

    Many truths that we have conjectured about reality have turned out to need a little fine tuning. Gravity is a force whereby mass attracts mass ... except that it doesn't: it is not a force but an illusion created by bodies in free-fall through curved space. Nothing can travel faster than light ... unless space itself is expanding faster than the speed of light. Nothing can communicate instantly over astronomical distances ... except entangled particles, and even in that case, curiously, no actual information can be transmitted.

    But if there is one thing we can be sure of it is that causality cannot be violated.

    https://en.wikipedia.org/wiki/Chronology_protection_conjecture
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