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Perpetual "Motion"

  1. Jun 30, 2014 #1
    So I have a somewhat naive question.

    Let's pretend that only an electron existed in a flat, static spacetime. That's all. We can boost to the rest frame of this electron to just say it's sitting there...doing nothing...in flat spacetime.

    Is there something not perpetual about this?
  2. jcsd
  3. Jun 30, 2014 #2


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  4. Jun 30, 2014 #3
    A perpetual motion DEVICE is a device, but there is also the concept of just perpetual motion (without a "device"). This is just motion going on indefinitely without the need to introduce new energy (you could also phrase it in the sense that entropy isn't increasing).

    However after posting this I realized that the system I setup isn't physical. Once you boost to the rest frame of the electron you know exactly how fast it's going therefore you can't know anything about where it is. This will cause the wavefunction of the electron to spread increasing the entropy. So projected onto what I CAN know (ie the wavefunction) there is a definite passing of time through the increased entropy of my increasing lack of knowledge of where the electron is. Or at least that's my logic at the moment haha
  5. Jun 30, 2014 #4


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    There's nothing wrong with "perpetual" motion if what you mean by perpetual motion is "inertial" motion.

    The problem is when someone claims to have a machine which continually extracts energy from a system without ever running out.
  6. Jun 30, 2014 #5


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    And the problem with this is that this violates of the law of conservation of energy.
  7. Jun 30, 2014 #6

    Is inertial motion possible without any other body in the universe?

    Moreover, how can motion be detected if there is nothing else in the universe?
  8. Jun 30, 2014 #7


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    Why wouldn't it be possible?

    If there's nothing else in the universe, then would it care either way?
  9. Jun 30, 2014 #8


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    Are you there to observe it? If so, you can simply define the reference frames.

    This scenario is yours so the answer can be pretty much whatever you want -- but that may not be compatible with reality.
  10. Jun 30, 2014 #9


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    It is perpetual, but it is also not prohibited by the laws of physics.
  11. Jul 1, 2014 #10
    A thread of mine has been closed because i didnt respond to a wrong question. So, i am cautios this time.

    But i cannot stop asking questions to what you have said.

    1. If reference frames can be so simply defined, it means we think of points in space. Then space ceases to be a continuum. Reference frames seem sensible when there are two particles at least.

    2. The scenario that u say is not compatible with reality hints that time itself may be a secondary phenomenon. We cannot even think of the passage of time if there is a single body in the universe. If you say that someone is there to observe it, it makes two things.
    Last edited: Jul 1, 2014
  12. Jul 1, 2014 #11
    what if the single body was you?
  13. Jul 1, 2014 #12

    When i say a single body, it is assumed that it is a body with no internal parts/mechanism.
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