🚀 go-pugleaf

In article <53011@cup.portal.com> Andrew_-_Palfreyman@cup.portal.com writes:
>J. Giles writes (quoting someone else, I think):
>:If I arbitrarily rearrange a DNA molecule, the _biological_ information
>:it contained is completely destroyed - it now contains _ZERO_ information
>:from a biological point of view.

This is wrong.  It is still a molecular machine which can select sub states,
see the reference given below.

>:[..]I think you'll find that the change in entropy depends on what is
>:considered a "blank" tape and what is considered "information" on a 
>:recorded tape.  It is not difficult to conceive of coding conventions 
>:in which the lowest entropy condition of the tape corresponds to a 
>:blank - completely erased - tape.

If we take information to be a negative decrease in uncertainty,
then this is meaningless, as you have not specified clearly the two
relevant states.

> In short, the change in entropy 
>:of a physical system used to record information depends on the
>:_interpretation_ which relates the physical system to the data
>:that it records.  What is the thermodynamic definition of an
>:interpretation? [..]

Negative decrease in uncertainty corresponds to selection of states.
Interpretation is not required.

>i'm glad you've brought this point up, Jim. when learning about statistical
>mechanics from Zemansky, i recall the "equation" there stating 
>	information = -log(entropy)
>perhaps not exactly; the point made was the link between the two in the
>context of thermodynamics.

You were thinking perhaps of the epitaph on Boltzmann's grave:

       S = - log W

At risk of repeating myself, see J. Theor. Biol. (1991) 148 83-137, and please
join us over on bionet.info-theory to discuss these issues in detail.

>as regards information, i'm always puzzled by the contrast between this
>posited thermodynamic equivalence and the fact that if something is
>*not surprising in the least*, it's not information.

This happens because most peoples definitions are messed up.

  Tom Schneider
  National Cancer Institute
  Laboratory of Mathematical Biology
  Frederick, Maryland  21702-1201
  toms@ncifcrf.gov