I read an article today that somwhat confused me. Is this the same as time travel...which I have always thought was a contradiction. Are they talking about reversing law of thermodynamics? In which case I don't know if this is the same as time reversal. Complicated topic....maybe someone can expalin in layman terms. below the link



The arrow of time is essentially just a different way of looking at the second law of thermodynamics. Essentially when we see entropy increase we are so "familiar" with it that we associate this with time progressing forward. I would say the arrow of time is a more subjective statement of the second law that relates to our perception.

If, by some mechanism, we observe entropy to decrease, it would look like time is flowing backwards. But this is not really going back in time, or what you would call "time travel". Essentially here the system just "became more ordered", going against the second law and thus appearing to move backwards in time.

  • $\begingroup$ you explain this very well...and have been most gracious.... ...i am very disappoineted in how the popular press states things in ways to get attention without paying attention to reality ...thank you for setting this topic straight $\endgroup$
    – user86411
    Mar 14 '19 at 1:20
  • $\begingroup$ @Sedumjoy Thank you. Yeah I saw the same thing come across my phone and I didn't even bother clicking on it haha $\endgroup$ Mar 14 '19 at 1:50
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    $\begingroup$ Let us hope that the wording time machine didn't originate by the scientists. It is also possible. $\endgroup$
    – Alchimista
    Mar 14 '19 at 9:40
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    $\begingroup$ The paradox is that subjectively we could never observe a large scale reversal of the second law of thermodynamics because memory only works in the direction of globally increasing entropy. $\endgroup$
    – gandalf61
    Mar 14 '19 at 13:34
  • $\begingroup$ @gandalf61 Right. If you were to somehow decrease the entropy everywhere without effecting memory, then I guess you would have created a "time machine"? Although there isn't only one unique "lower entropy universe", so you might not be traveling back to the correct past. Sounds like a fun sci-fi concept to me :) $\endgroup$ Mar 14 '19 at 13:36

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