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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: 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?

    --
    "I guess once you start doubting, there's no end to it." -Batou, Ghost in the Shell: Stand Alone Complex
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  • (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).