Arthur asked:

A problem arose to my mind while reading about the 2nd law of thermodynamics, it says that "the
overall disturbance in a closed system must increase or at least remain constant but never decrease"
but the problem here is that the "disturbance" is something to humans, WE think that scattered billiard
balls are disturbance and think that when they take the shape of a triangle (at the beginning of the
game) they are not disturbed, so how can something related to humans take place in an impersonal
physical law?

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Entropy measures the disorder of a system. This term is not a term expressing approval or
disapproval it just refers to the fact that e.g. molecules in ice are tighter packed than in liquid water,
which in turn has a higher level of organisation compared to gas molecules in steam. This difference
in the organisation of matter can be objectively measured (e.g. via the energy levels and the
properties of the system) i.e. is not dependent on human beings. The 2nd law simply says that the
entropy (disorder) of the universe overall increases. [If the volume and energy of a system are
constant, then every change to the system increases the energy].Things get broken, living beings die
and decay ... Whenever you want to create order out of disorder you need to put energy into it (e.g. it
is easy to break a cup but difficult to put it back together), and part of that energy is irretrievably lost
as heat, thus increasing the overall disorder of the system.

Helene Dumitriu

This is actually sort of an interesting point. The term "disturbance" is indeed an odd one, to me at
least. I would have said something like "smoothness", "randomness", or "uniformity". But aside from
that, one could still object that we perceive certain patterns or types of patterns as order, and certain
other patterns as disorder, and so this distinction is a purely human one.

There are a couple of ways around this, however. First, there are only a small number of ways that
billiard balls can be put into a triangle, and many hundreds or thousands of ways they can be
scattered over the table. One could say, then, that what we are actually comparing is the probability
of them being in the relatively small number of distributions we term "ordered" versus the huge
number we term "disordered", and so that probability governs the frequency of those distributions
actually seen. Not unreasonable, but we can still ask why some subset of the "disordered" set is not
perceived as a distinct subset, as the "ordered" sets are, i.e., whether there is any real difference
between what we perceive as ordered and what we perceive as disordered.

I wondered this myself for quite a while, until I saw the results of the work of G. Chaitin. What he did
was to show that there is a difference in the minimum length of formulas which describe various
states of affairs, mostly in formal systems. But this is an interesting result in this context, because we
can see that symmetrical groupings will have smaller descriptions (because of the identity of
rotations) than asymmetrical and chaotic groupings. Those latter will have to be described by larger
formulations, because we can't abbreviate for the symmetry in them. Now, no matter who is doing the
describing: us, aliens, mother nature, or whatever, that's going to be true. So that is, I think, a nice
way to relate more and less random distributions in some reasonably absolute way, and leads to the
same types of classifications that our intuitions do, which is rather heartening metaphysically, when
you think about it. The interesting implication is that description has to do with composition, a very
strange result for me, at any rate... but consistent with the Second Law, it seems.

Steven Ravett Brown

I am not a physicist, but it seems to me that you are too bothered by the term "disturbance" which
may just be used in a technical way by physicists.

Ken Stern

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