Re: "Randomness" in different branches of science

Moorad Alexanian (alexanian@UNCWIL.EDU)
Mon, 23 Feb 1998 14:03:30 -0500 (EST)

At 11:31 AM 2/23/98 -0500, Loren Haarsma wrote:
>Moorad Alexanian wrote:
>> In quantum mechanics there is a dynamical theory that indicates the possible
>> outcomes of given experimental measurements and the associated probabilities
>> for such outcomes. Can someone tell me what is the dynamical theory that
>> tells us what are the possible outcomes and the associated probabilities in
>> evolutionary theory? Any theory that uses the notion of randomness must
>> makes such issues clear; otherwise, it is not a scientific theory and are
>> mere words
>What about the optometrist who told me that I have twice the usual
>probability of developing gloucoma during my lifetime because of an eye
>injury when I was sixteen? He didn't have a dynamical theory, but I'd
>still say that he was being "scientific." What about researchers
>claiming that moderate alcohol consumption reduces the risk of heart
>disease, or the more recent report that above-moderate alcohol
>consumption increases the risk of breast cancer? They have only a few
>clues about underlying mechanisms, which might or might not be correct.
>But it sounds like science.

I never said that one cannot make predictions without a dynamical theory.
What I said is that there is no dynamical theory underlying evolutionary
theory--in the sense of the way the word theory is used in physics. Actuary
tables indicate life expectancies and so on but can never tell when you are
actually going to die. Notice that there is a BIG difference between not
being able to predicate when a particular atom will decay and when you will
die. The former is a rather simple system, the latter may be infinitely complex.

>Different sub-branches of science use randomness in slightly different
>ways, depending on how much empirical detail is known about the
>underlying microscopic mechanisms..
>In quantum mechanics, as currently formulated, results of measurements
>*in principle* are undetermined and probabilitistic.

The indeterminacy resides actually in nature and not in the inabilities of
man to theorize. Quantum mechanics describes the most information that we
can have---which is the possible outcomes and probabilities for all sorts of

>By contrast, in classical mechanics of complex systems the underlying
>mechanisms are very well understood and deterministic, but in practice
>the initial conditions cannot be specified exactly enough to allow the
>final state to be determined. By use of general principles (e.g.
>conservation of energy) and/or by Monte Carlo calculations,
>probabilities can be assigned to final macrostates.

There is a dynamical theory which gives results which are applicable to
systems with many particles and/or large number of degrees of freedom. You
do not get something from nothing.

>Different still, medical researchers can often assign probabilistic
>outcomes to scenarios --- based on observational studies --- while
>having only the vaguest ideas (if any) about the mechanisms underlying
>the effect.

That is why medicine is still an art and not a science--in the sense of
physics being a science.

>Most of biological research is somewhere between classical mechanics and
>medical studies. For example, in my last research project I measured
>changes in electrical conductivity in a single neuronal ion channel. By
>measuring conductivity changes as a function of voltage, time, etc. I
>could build a dynamical model of its behavior and learn something about
>how many distinct structural states it had. I can't tell you much about
>the actual structural states --- which amino acids shifted how far
>relative to each other. I can only tell you by observation how the
>channel's conductivity changes stochastically, and what the rate
>constants are. But given only that much knowledge, about this and other
>channels, without knowing the underlying structural dynamics, we can
>build exquisite models of how nerve cells fire and propagate action

In physics we call that phenomenology not theory.

>Historical sciences cannot have more detailed empirical/predictive
>content than the experimental and observational sciences upon which they
>are based. Consider a very simple experiment in microevolution: a dish
>of bacteria grown from a single cell line, subjected to mutagens and/or
>environmental stress. How will the bacteria evolve? We don't have a
>dynamical theory to predict the outcome. We can measure the average
>mutation rates from different doses of mutagens, but then we're stuck,
>because we don't have dynamical models of how even single cells work.
>I'm hopeful that within four to ten decades we will have detailed,
>empirical models of cellular physiology, at which point we can predict
>the consequences of a single mutation in a single-celled organism.
>Imagine how much more difficult it will be to empirically predict
>changes in multi-cellular organisms, or whole populations living in a
>complex environment.

That is why I say questions in biology, etc. are much more difficult than in
physics in the sense that it is extremely difficult to develop theories in
biology like we do in physics.

>If that's the case, of what use are the historical sciences? Quite a
>lot, in turns out. By starting with what is known about the
>deterministic and stochastic processes, building models, and comparing
>it to observation, constraints can be put on those underlying processes
>and, sometimes, spectacular predictions can be made. Cosmologists used
>particle physics and astronomical data to contrain how many different
>types of leptons and hadrons could possibly exist --- something the
>particle physicists couldn't determine by particle-smashing alone.
>Before the discovery of nuclear energy, geologists who measured the age
>of the earth could tell astronomers that some unknown mechanism was
>needed to supply energy for the sun. Evolutionary biologists can make
>predictions about genetic homologies amongst different species.

Historical sciences are OK provided they keep their claims within bounds and
don't go beyond what the date indicates. We ought not to get philosophical
conclusions from historical sciences.

>When I started learning quantum field theory, my professor put this
>diagram on the board:
> Classical ______________ Quantum
> Mechanics Mechanics
> | |
> | |
> | |
> Classical Quantum
> Field ________________ Field
> Theory Theory
>His point was that you could get from the intuitively understood
>classical mechanics to the truly weird QFT (my words, not his) in two
>resonable steps by two pathways. You can transform mechanical variables
>(energy, momentum, etc.) into classical field variables, the convert
>those field variables into quantum field operators; or you could first
>convert mechanical variables into quantum mechanical operators, then
>convert those operators into field operators.
>When thinking about the different natural sciences, I like this diagram:
> Experimental Observational Historical
> Physical ------------ Physical --------- Physical
> Sciences Sciences Sciences
> | | |
> | | |
> | | |
> Experimental Observational Historical
> Biological ------------ Biological -------- Biological
> Sciences Sciences Sciences
>Consider the vastly increased complexity when going from physical to
>biological sciences. Consider the necessary changes in methodology and
>empirical content as you move from experimental to observational to
>historical sciences. Scientifically, it looks to me that the
>evolutionary biologists (when they talk science and not metaphysics) are
>using "randomness" in appropriate ways for their sub-discipline.
>Theologically, if God can providentially guide simple, every-day
>physical systems like the casting of lots, how much more over complex
>biological systems over long periods of time.
>Loren Haarsma

It seems to me that the evolutionary biologists assume a picture and want to
fit the data to it. I have no qualms with that. But do not tell me that the
original picture is fact. Again I say that it is very doubtful for the
evolutionary biologist to ever get to describe their subject matter in the
mathematical depth that governs the notion of theories in physics.