Re: [Phys-L] causality

[John Denker <jsd@av8n.com>]

On 2/8/19 6:18 AM, Daniel MacIsaac wrote:

> What do you think about the MinutePhysics videos taken from the book by
> Sean Carroll: The Big Picture

Sean Carroll is a smart guy, but he is somewhat gaffe-prone, and
the problem is magnified when other people repackage his work.

> on complexity, entropy and causality at 
> <https://youtu.be/yKbJ9leUNDE>  ??

As for that video in particular:
1) I agree with the overall sentiment and with 99% of the details, but
2) there are a couple of gaffes:
 ++ Fact:  According to all evidence available to me, and
  according to my own analysis, the second law of thermodynamics
  applies to *everything* including microscopic as well as
  macroscopic systems.  This is important, because otherwise
  there would be loopholes in the law.  Also, many pedagogically
  valuable hands-on examples of entropy are microscopic.
 -- In a couple of places, the video says the second law of
  is somehow "macroscopic" in contrast to Newton's laws which
  are "microscopic".

 ++ Fact:  Entropy is defined in terms of probability.  It is
  a property of the thermodynamic macrostate as a whole, i.e.
  of the ensemble as a whole -- not a property of any particular
  microstate.
 -- The video improperly (and quite unnecessarily) throws in the
  word "disorder" as a synonym for entropy.  Disorder, insofar
  as it can be quantified at all, is a property of the microstate.
  Looking at a disorderly state, you have no way of knowing whether
  the distribution (if any) from which it came is a high-entropy
  or low-entropy distribution.