[Martin Taylor 2018.04.06.15.29]
[Bruce Nevin 2018-04-06_11:34:00 PT]
Good check point. The lead-in to this April 4 popsci article
does include the word “fool”.
Further checking the author's references, this was
published in October
https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.117.170401
The attached 2nd-Law-broken.pdf, published in July, seems
to be a follow-up popularization.
Joseph Nils Becker has done considerable work on control of
quantum states in diamonds at Oxford
https://www.researchgate.net/scientific-contributions/2084525317_Jonas_Nils_Becker
where Ian Walmsley has indeed demonstrated quantum effects
in the operation of microscopic heat engines.
https://arxiv.org/abs/1710.08716
The short paper you posted was interesting, in that I used to have
on my web site a live demonstration of exactly this small-scale
effect of entropy in a small isolated system increasing and
decreasing erratically, but it long ago stopped working because of
changes in Java, and I never bothered to upgrade it. The second law
is not broken at all. It only seems broken because of the enormous
degree of statistical smoothing in its large-scale (Clausius) form,
where the number of interacting entities (atoms, say) is of the
order of Avogadro’s number (6 * 1024 approximately). When
a system gets small, the interactions between the small number of
degrees of freedom being monitored and the wider Universe can easily
lead the entropy of the small system to go up and down. It’s true
even in an isolated small system. There’s no quantum magic about
that. It’s just a consequence of the fact that the Law of Large
Numbers is just a law of large numbers.
The so-called "arrow of time" implicated in the ever-increasing
entropy of an isolated system can easily reverse in a tiny system
simply because there aren’t enough degrees of freedom to smooth the
statistics. Sometimes one degree of freedom by chance gets a lot of
energy from all the others, which “cool” right down because of
conservation of energy, decreasing the overall entropy of the
system. One of my favourite Physics book series as a child was
George Gamow’s “Mr Tomkins” series. I remember two titles “Mr.
Tomkins in Wonderland” and “Mr. Tomkins Explores the Atom”. In one
of them, Mr Tomkins wakes from his exploration that explained the
Boltzmann-Gibbs approach to entropy to find his drink freezing on
one side of the glass and boiling on the other. It was a physical
possibility, but would have been very unlikely to have been observed
in the age of the Universe.
The observation of Mr Tomkins's glass is physically possible, but
has nothing to do with time reversal. It simply has to do with the
fact that it’s much easier to find your way out of a small
(unlikely) region of a possibility space than it is to find your way
back to the unlikely region by random moves. There’s no breaking of
the second law in it’s Boltzmann-Gibbs form where “entropy” is
determined by the sizes of spaces of possible states that are “the
same” from some observational viewpoint, though there is in the
Clausius form that applies only to bulk systems. Mis-applying laws
can get them broken any time you want, as magicians know very well.
Martin
···
On Fri, Apr 6, 2018 at 11:00 AM, Martin
Taylor mmt-csg@mmtaylor.net
wrote:
[Martin Taylor 2018.04.06.13.51]
[Bruce Nevin 2018-04-06_10:20:36 PT]
"Living things constantly strive
against the second law of thermodynamics,
sucking in energy to maintain the order
within their cells. Powering all this are
our bodies’ equivalent of heat engines:
mitochondria. So here’s an intriguing
question: given that natural selection
tends to encourage efficiency, has biology
evolved quantum heat engines? There is a
hot debate about whether any quantum
effects are important in biology, but in
my opinion it’s not crazy to think that
evolution would produce the most efficient
engines possible."
The article is attached; you need a
subscription to see it on the site at
https://www.newscientist.com/article/mg23731720-400-im-building-a-machine-that-breaks-the-rules-of-reality/
That article was published on the closest available date
to April 1, was it not? There are a few little details
that would concern me and might perhaps induce me to
enquire further had it been published in, say, June.
I grant that not all suspect articles published around
April 1 are spoofs. The first article I ever saw on masers
was in an April 1 issue, and I thought it must be a spoof,
but it wasn’t. Maybe this also is not, but if it isn’t,
why does it rely on the gross thermodynamic statement of
the second law as a law, rather than on Boltzmann’s (or
Gibbs) probabilistic reasoning for why the law is in
practice almost always observed? The probabilistic
approach to entropy would seem more appropriate to a
quantum discussion, would it not?
Martin