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posted by martyb on Friday December 04 2015, @03:27AM   Printer-friendly
from the arrow-of-time-goes-only-one-way? dept.

Researchers at the Federal University of ABC, in Brazil, have made a major breakthrough: they've confirmed that thermodynamic processes cannot be reversed, even in a quantum system. This revelation not only explains a fundamental aspect of our universe but could also influence how quantum computing systems are designed.

[...] The microscopic and macroscopic worlds currently operate using two different standards -- general relativity governs the macroscopic world while quantum physics rules the microscopic. In our macro world view, thermodynamic (entropic) processes only move in one direction. That is, using an egg analogy, you can't uncook an egg much less get it to hop back into its shell and seal the crack. But in the subatomic world, many of these processes are "time-symmetric" -- essentially, they're reversible.

However, what Tiago Batalhão and his team at the UFABC discovered actually runs counter to our expectations. Their experiment sought to measure the entropy change within a closed system of carbon-13 atoms submerged in liquid chloroform while they're subjected to an oscillating magnetic field. The idea is that polarizing the field should cause the atoms' nuclear spins to all rotate one direction, while reversing the field's polarity would make their spins flip and rotate the opposite direction.

Now, if this process were time-symmetric as our current understanding of physics dictates, the atoms' spins should flip back and forth without issue and return to their initial states once the magnet was turned off. But the UFABC team found that the atoms' spins couldn't keep up with the magnet's oscillation rate and some would eventually fall out of sync with their neighbors. This means that entropy within the closed system was actually increasing -- precisely the opposite effect from what should be happening. It effectively proves that thermodynamic processes are not reversible at the quantum level. What's more, it reveals a disconnect between the current laws of physics and what we're actually observing.

Yet, earlier this year scientists did figure out how to unboil eggs...


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  • (Score: 0) by Anonymous Coward on Friday December 04 2015, @03:37AM

    by Anonymous Coward on Friday December 04 2015, @03:37AM (#271681)

    An experiment can disprove, but cannot prove hypothesis/theory.

    • (Score: 0) by Anonymous Coward on Friday December 04 2015, @05:18AM

      by Anonymous Coward on Friday December 04 2015, @05:18AM (#271698)

      I can do neither. It can provide evidence, not prove, against the null hypothesis.

      • (Score: 0) by Anonymous Coward on Friday December 04 2015, @05:22AM

        by Anonymous Coward on Friday December 04 2015, @05:22AM (#271699)

        It, not I

        I presume you mean

        • (Score: 2) by xav on Saturday December 05 2015, @12:56AM

          by xav (5579) on Saturday December 05 2015, @12:56AM (#272028)

          Stop speaking to yourself, please.

    • (Score: 3, Informative) by aristarchus on Friday December 04 2015, @06:32AM

      by aristarchus (2645) on Friday December 04 2015, @06:32AM (#271708) Journal

      An experiment can disprove, but cannot prove hypothesis/theory.

      So let me lay it out for you: we are disproving that thermodynamic processes can be reversed. We are not proving that they cannot. Which means what? You still have to prove they can, you and Wheels. Who knew that Dr. Sheldon Cooper was a Soylentil?

      --
      "Believe it or not, your opinion on this topic is really not necessary,"
  • (Score: 2) by NotSanguine on Friday December 04 2015, @03:44AM

    The result of this experiment is suggesting that the Second Law of Thermodynamics [wikipedia.org] applies at a quantum level.

    IANAP and I did not read TFA, so perhaps I'm missing something here.

    --
    No, no, you're not thinking; you're just being logical. --Niels Bohr
  • (Score: 2) by Appalbarry on Friday December 04 2015, @03:57AM

    by Appalbarry (66) on Friday December 04 2015, @03:57AM (#271690) Journal

    Surely there is nothing in this universe that can't fixed with a 3D printer?

    Or so I've been told.

    • (Score: 0) by Anonymous Coward on Friday December 04 2015, @04:24AM

      by Anonymous Coward on Friday December 04 2015, @04:24AM (#271693)

      Or indirection and caching.

    • (Score: 1, Funny) by Anonymous Coward on Friday December 04 2015, @01:25PM

      by Anonymous Coward on Friday December 04 2015, @01:25PM (#271777)

      Systemd will save the universe from entropic heat-death.

      • (Score: 0) by Anonymous Coward on Friday December 04 2015, @01:35PM

        by Anonymous Coward on Friday December 04 2015, @01:35PM (#271779)

        I thought Multivac would.

  • (Score: 3, Informative) by Anonymous Coward on Friday December 04 2015, @04:32AM

    by Anonymous Coward on Friday December 04 2015, @04:32AM (#271695)

    "That is, using an egg analogy, you can't uncook an egg much less get it to hop back into its shell and seal the crack without addition of external energy.

    • (Score: 0) by Anonymous Coward on Friday December 04 2015, @03:54PM

      by Anonymous Coward on Friday December 04 2015, @03:54PM (#271823)

      But Humpty had the strength of all the king's horses AND all the king's men!
      Surely that would be enough energy to put him back together again?

  • (Score: 2) by jasassin on Friday December 04 2015, @05:32AM

    by jasassin (3566) <jasassin@gmail.com> on Friday December 04 2015, @05:32AM (#271700) Journal

    I have this recurring nightmare of a puddle of water interacting with entropy and solidifying back into a cube.

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    • (Score: 2) by xav on Saturday December 05 2015, @01:02AM

      by xav (5579) on Saturday December 05 2015, @01:02AM (#272030)

      I guess your bed sheet are soiled when you finally wake up.

  • (Score: 2) by darkfeline on Friday December 04 2015, @05:41AM

    by darkfeline (1030) on Friday December 04 2015, @05:41AM (#271702) Homepage

    So the world really is time asymmetric? I guess that disproves Merlin, for starters.

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    • (Score: 2) by HiThere on Friday December 04 2015, @09:26PM

      by HiThere (866) on Friday December 04 2015, @09:26PM (#271957) Journal

      Which Merlin? If you're talking about the Disney version, what disprove him is that an electron moving backwards in time is (cannonically isomorphic to) a positron. So he'd explode.

      --
      Javascript is what you use to allow unknown third parties to run software you have no idea about on your computer.
  • (Score: 3, Touché) by MostCynical on Friday December 04 2015, @08:00AM

    by MostCynical (2589) on Friday December 04 2015, @08:00AM (#271718) Journal

    https://en.wikipedia.org/wiki/Humpty_Dumpty [wikipedia.org]

    On-topic, is this evidence against time travel?

    --
    Books are a poor substitute for female companionship, but they are easier to find. P Rothfuss “The Wise Man's Fear"
    • (Score: 2, Informative) by Anonymous Coward on Friday December 04 2015, @08:48AM

      by Anonymous Coward on Friday December 04 2015, @08:48AM (#271735)

      Not necessary.

      It just goes to show that entropy is not time position dependent, but knowledge (information) dependent. Imagine classic demonstration: suppose you get an empty transparent acrylic box which can house three layers of same number of identical ping-pong balls per layer. You fill the bottom raw with white balls, then fill another layer of balls, but paint them in different color. Leave the third layer empty.

      Put the lid on, turn the camera on, then shake the box.

      The recording will show how entropy rises with time, as the balls in layers get mixed. If you play the recording in reverse, it would seem that entropy decreases (with time flowing backwards).

      However, imagine that you could edit the video, identify each individual ball and reassign their colors at the end of experiment (after the shake) and then follow their path back through time. You would see that if you proclaim the state of the system after the shake as ordered, then entropy increases in direction opposite to the "arrow of time".

      So, entropy is sort of measure of "time distance traveled" in either direction, from arbitrary selected "ordered" state of the system (or iow from state of the system at arbitrary selected time coordinate).

  • (Score: 2, Insightful) by Anonymous Coward on Friday December 04 2015, @08:13AM

    by Anonymous Coward on Friday December 04 2015, @08:13AM (#271719)

    What's more, it reveals a disconnect between the current laws of physics and what we're actually observing.

    No, it doesn't.

    To quote from the actual scientific article: [aps.org]

    Let us discuss the physical origin of such time asymmetry in a closed quantum system. Using an argument put forward by Loschmidt in the classical context, its time evolution should in principle be fully reversible [1]. How then can a unitary equation, like the Schrödinger equation, lead to Eq. (1) that contains a strictly non-negative relative entropy? The answer to this puzzling question lies in the observation that the description of physical processes requires both equations of motion and initial conditions [1,13]. The choice of an initial thermal equilibrium state singles out a particular value of the entropy, breaks time-reversal invariance, and thus leads to the arrow of time. The dynamics can only be fully reversible for a genuine equilibrium process for which the entropy production vanishes at all times. Moreover, issues linked to the “complexity” of the preparation of the initial state to be used in the forward dynamics (or the corresponding one associated with the time-reversed evolution) have to be considered [33].

    So there's nothing missing in our laws of physics, they can explain the observed behaviour quite fine.

  • (Score: 2) by Dunbal on Friday December 04 2015, @01:47PM

    by Dunbal (3515) on Friday December 04 2015, @01:47PM (#271780)

    And yet a hen lays a perfect egg every single day. Quantum hens!