🚀 go-pugleaf

Steven B. Harris wrote:
>    But you get your molecules scrambled all the time!  Thermal motion
> knocks them around and back and forth.  Molecules get broken down and
> replaced, so that after a decade a lot (probably most) of your atoms
> are not even the same, but have been replaced by different (though
> identical) atoms from your diet.  Does that make you not you?

Sure. But when you say "scrambled" you seem to think it means
"random", and -- of course -- it ain't. Which bonds get broken or
where thermal motion takes "molecules" (not very far, as it turns out --
thermal motion applies more to electrons) isn't random noise, but
highly-correlated noise. These correlations, themselves, constitute
important information about the system -- aka "you" -- we're talking
about.

Complex systems are "more" than just the sum of the parts. They have
layers of so-called "emergent" properties that represent important
details about the system.

We can get SOME idea of this by considering a much simpler example
where "the positions of the parts" don't give us much.

Consider the solar system. Suppose I asked you to construct a copy,
only given the information about the positions of the planets
(and, perhaps, all the asteroids down to a certain size). Would it
be a functioning copy of the solar system we know and love?

No. Even if you deduced the rotational motions from "average
considerations" of those positions (e.g. you knew the various Keplerian
laws) the system would not be a copy of the "real" solar system even for
an instant. It might be an "approximate" copy, of course.

The system, then, is not just the positions of the particles, but
their relative motions as well. The "relative motion" concept is a
simple emergent property -- it takes 2 particles to make sense, and
3 or more particles to make *really* complex. (Although, these days,
the N-body problem seems to have been "solved" analytically).

To take the same example further, and run it into the ground ;-),
if you watched this "duplicate system" evolve it would likely never
produce life on earth. The reason -- you forgot to model the Oort cloud
which seems to have been an important source of biological material.

Another complication that seems to crop up when dealing with quantum
systems -- beside indeterminacy (which, after all, may be just a
consequence of deterministic chaos) -- is the "action at a distance"
stuff that seems to have gained currency through the EPR and GHZ
experiments. I.e. in quantum systems it isn't a matter of just where
particles are, and how they move, but ALSO whom they knew in the distant
past! And due to (at least) chaotic effects such knowlege is so mixed up
in the system that it's virtually impossible to determine in complete
detail.

R. Kym Horsell
KHorsell@EE.LaTrobe.EDU.AU                  Kym@CS.Binghamton.EDU
http://www.ee.latrobe.edu.au/~khorsell     
http://cs.binghamton.edu/~kym