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Thought experiment proposed to reconcile psychological versus thermodynamic arrows of time:
A pair of physicists has proposed a thought experiment to help reconcile the seeming disparity between the psychological and thermodynamic arrows of time. In their paper published in the journal Physical Review E, Leonard Mlodinow and Todd Brun claim their thought experiment demonstrates that the two seemingly contradictory views of time, must always align.
When ordinary people think about time, they see the past as something that has come before and the future as a great unknown yet to come. We can remember the past, because it has happened already, but not the future, because it hasn't. Physicists, on the other hand see time as able to move either forward or backwards (towards greater entropy), which implies that we should be able to remember events in the future. So, why can't we?
It's because of the way our memories work the two say, and they've created a thought experiment to demonstrate what they mean. Imagine, they write, two chambers connected by an atomic sized tube with a turnstile in it. If there is gas in one of the chambers, individual atoms of it will move through the tube to the other chamber (towards higher entropy) tripping the turnstile as they go, in effect, counting the atoms as they pass by, until both sides have equal numbers of atoms-creating a state of equilibrium.
http://phys.org/news/2014-05-thought-psychological -thermodynamic-arrows.html
http://physics.aps.org/articles/v7/47
http://journals.aps.org/pre/abstract/10.1103/PhysR evE.89.052102
(Score: 2) by HiThere on Tuesday May 06 2014, @07:16PM
Sorry, but neither the past nor the future are determined. The wave function doesn't collapse for more than an instant...i.e., only in whatever instant is "now". Possibly the spread of potential is slower in the past than in the future, but both are deterministic in the large (e.g., planetary orbits, for periods of less then a thousand years...after that things start getting flaky) and both are non-deterministic in the small (e.g. position of an electron). We live on the interface between large and small, for the periods of time we consider normal. Over really large periods of time planetary orbits are also non-deterministic. Over really short periods of time, electron positions are fairly well determined, based on how well we knew their starting characteristics.
So "the future hasn't been defined yet" isn't a good answer. But the past being "relatively" fixed might be. Just don't confuse "relatively fixed" with actually fixed. Even so... I don't think it's that simple. I think it probably *does* have to do with the flow of entropy at the chemical bond level. So if you explain thermodynamics, you explain the arrow of time. But it's statistical. Also, you put more faith in your memory than it deserves...you can't go back and check on it, but it's not accurate the way a recording is, and even those have an error rate.
But it's even less determined than I suggested. I was describing things as if there were a universal time. Actually, though, "now" isn't well defined except for a nanoscopically small area. Once you get out of the "fuzziness of a photon" around a locale, there is no well defined now where the state wave is collapsed. This is actually what the "Wigner's friend" paradox is describing.
Personally, I find the easiest model of the universe to use is Multi-Worlds interpretation of quantum theory, though I acknowledge that it isn't the only valid interpretation. The thing is that there are several interpretations that all are consistent with the available evidence, so choosing between them is currently a matter of taste. A Super-determinist would chose to see everything as deterministic, even though that was only one possible interpretation. (In fact, the Multi-World interpretation could, itself, be seen as a form of Super-determinism.) The descriptions of the different interpretations sound very different in English, but they make the exact same predictions (as far as can be tested) about matters of fact.
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