Re: [Phys-l] setting-time-aright

[John Denker <jsd@av8n.com>]

On 09/02/2011 06:22 AM, chuck britton wrote:
> http://www.slideshare.net/seanmcarroll/setting-time-aright
>
> some thoughts - Kologomorov et al.

I don't know what to make of this.  I was considering two possible
mini-reviews:
  a) The charitable version says "This is wrong as to most details, 
   but it doesn't matter because the conclusion isn't affected by
   those details"
  b) The less-charitable version says "This is wrong as to most
   details and wrong as to the conclusion."

Then I realized that I have no idea what the conclusion is, no
idea what the point is.  Is the point that the past is different
from the future because of entropy?  
 1) That's not an original idea, and
 2) to make it work, you need a rather detailed understanding
  of how entropy works, especially given that the fundamental
  equations of motion are /unitary/ i.e. reversible ... and 
  the slideshow doesn't even hint at these issues, let alone 
  address them.

Is the point that "the purpose of life is to generate carbon
dioxide"?  That's a ridiculous answer to a ridiculous question.

Using a messy room to represent entropy is a not-very-apt cliché.
Disorder is a property of the microstate, while entropy is a
property of the macrostate.  The same issue arises in connection
with complexity, leading to the proverb that says "all strings
are complex, except for the ones we know about".  There is a
"constant" that appears in the definition of complexity, which
is often dismissed as unimportant, but is in fact very important
in situations such as this.

Entropy is /not/ generally equal to ln(W).  Boltzmann himself
was aware of this.  (I am quite aware of what it says on
Boltzmann's tombstone, but I'm pretty sure he didn't put it
there.)

The alleged mismatch between entropy and complexity bespeaks
a non-understanding of entropy, or of complexity, or both.
As for the slide showing two liquids mixing:  It is easy to 
misunderstand the entropy of mixing one sample of chocolate 
milk with another, because of the entropy of the deal, as we 
have recently discussed in this forum.  See also
  http://www.av8n.com/physics/thermo/z-particles.html#sec-ideal-z-deal

As for the slide that talks about "empty space forever" ...
that grossly abuses the meaning of the second law.  The law 
talks about the entropy of a given parcel.  If you change
your definition of what the parcel is, and/or if you allow
entropy to flow across the boundary of the parcel, you have
to take that into account.

> some thoughts

Not very careful thoughts.  Not very useful thoughts.