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Arrows of time

  1. Aug 16, 2005 #1
    I've read that there is a thermodynamic arrow of time, based on the fact that entropy can only increase or stay at the same level. But why is it thought to be directed in the same direction as the psychological arrow of time. Could there be an arrow of time directed in the opposite direction to our psychological arrow of time, so that time moves forward (or backward relative to the the psych' arrow) with decreaseing entropy. If on a macro scale time moved the opposite direction to the psychological arrow we humans wouldn't be able to tell the difference easily, since our memories would still be of the past (the past according the our psychological arrow of time that is).
  2. jcsd
  3. Aug 16, 2005 #2
    Psychologically, you never percieve a broken glass reassembling itself and jumping
    up onto the table.

    Even if you flipped a switch and reversed time abruptly, things would flow
    psychologically forward after only a short time even though the time evolution
    of the universe was formally reversed.

    That is, you drop a glass and it shatters. If at the instant of shattering, you could
    reverse the flow of time (say by putting a negative sign on Planck's constant) then
    the glass would start to reassemble itself. But very quickly, it would start to
    deviate from this psychologically reversed behavior and fail to reassemble. This is
    because even backwards the laws of statistical mechanics work, and there are
    many many more ways for a glass to break [and subsequently fail to reassemble]
    than there are ways for them to correctly reassemble.

    The mathematical equations of time work the same way forward or backward, but
    the statisitcal mechanics of many-body interaction always results in an increasing
    entropy which is what gives rise to the psychological perception of time (and the
    actual reality that broken glasses never reassemble themselves.)

    I now speculate that for a brief time, maybe milliseconds, your memories
    would start to unwind as well, but very quickly they would start to be
    recorded again because your memories are a lot like the history of a breaking
    glass. If it fails to reassemble, then there's no reason to think that your
    memories would all unwind in time either.
    Last edited: Aug 16, 2005
  4. Aug 16, 2005 #3
    Edited: I realise now that you said the laws of statistical mechanics still hold with time flowing in the other direction. Why is that, if there's an easy way of explaining?
    Last edited: Aug 16, 2005
  5. Aug 16, 2005 #4
    But then the recombination of the glass would be scale dependant?..you could for instance have a path-integral that recombines the Glass at the planck scale. This could decrease the Entropy in our Scale-Universe, whilst increasing the Entropy at the planck scale.

    There was a theory once, where the planck scale was determined as being "another-universe". I dont recall who came to this conclusion, but remember this was the outcome for MWI?

    By the way, what is the field-entropy?..where does the Entropic Arrow point?
  6. Aug 17, 2005 #5


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    The two quantities, our psychological perception of time and the increase of entropy, are not themselves directly comparable (in the mathematical sense), so the directions of the "arrows" associated with them are completely arbitrary. If entropy were decreasing with our psychological perception, then it would still be called an arrow of time.

    It may be that our perception of time is directly impacted by changing entropy, but this is just speculation. When people usually talk about arrows of time, they mean only that something is changing consistently in the same direction with our perception of time.
  7. Aug 17, 2005 #6
    There was another identical thread posted some weaks ago, but I cannot find it.

    Yes, this is because processes happen all the time with continuity.
    Last edited: Aug 17, 2005
  8. Aug 27, 2005 #7
    We know that time is not a product of Gravity because if Gravity ceased to function then time would still continue, Things would just float around in Zero Gravity.

    If all energy ceased to function then Time will stop.
    If all Matter ceased to function then time will stop.

    Time must be a product of Matter and Energy and not Gravity but Gravity is a product of Matter and Energy, Seems Gravity is inbetween a rock and a hard place.

    If a person grows old then they perceive they're is a value of time, But actually the reason a person grows old is because they're genes are decaying into less information.

    Every time the cells in our bodies replicate some of its information gets lost, This causes a breakdown in the memory of our genes which makes us look old after middle age, This is usually when the memory in our genes begins to lose the most information and eventually leads to death in old age due to a malfunctioning system.

    If we can keep our genes from loosing information during replication then it's quite possible to live forever.

    Getting back to Time, Time is a product of Matter and energy, To travel backwards in time is to become one with the past, This is a very complex thing to comprehend, If you approach the speed of light then time slows down, so it is said, Approaching the speed of light with a normal space ship that could achieve this hypothetally would only traverse into the future faster and not backwards in time, In order for a ship to go backwards in time that ship would require a computer so intelligent and faster than lightning to comprehend the cycles of the universe so that the time travel ship could harmonically become one with ancient space time which is different than todays universal harmonics, Is the Harmonics of the Universe's frequency getting faster or is it getting slower, Due to the knowledge that energy decays with forward time then the Harmonics must of been faster in ancient times, The traveler would have to attenuate the time travel machine or ship to the Quantum fluxuations of ancient past as well as kick ass to the speed of light to increase the amount of time that flows in the new direction.

    Ancient Time is like a Phone Number that can be dialed in, The Harmonics of time, The Velocity is how fast the signal is sent, And you would be the signal.

    Just my thoughts.
    Gerald L. Blakley
    Last edited: Aug 27, 2005
  9. Aug 27, 2005 #8


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    Please read the PF guideline on posting, especially regarding speculative posts.

    Furthermore, you made several errors in understanding of physics to base your speculation. For example:

    This is, unfortunately, a very common misinterpretation of Special Relativity. If you are approaching the speed of light, YOUR TIME doesn't change a bit ACCORDING TO YOU. Your time will only slow down from the perspective on ANOTHER observer in another reference frame that sees you moving with such velocity.

    Do not use various principles of physics that you do not fully understand to form your "opinion". If you do that, you are building something on very shaky foundation.

    Again, if you wish to make your own speculative posts, please refer to our Guidelines and the IR section of this forum.

  10. Aug 27, 2005 #9
    Hi Zap.

    Cool with me.

    I do know about relativity of an observer, I just didn't speculate it, but it is what I ment, My appologies.

    Gerald L. Blakley
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