Hey this is fun, and informative, so until the boss tells us to lay off I'll
put in a bit more.
First of all, definition of prediction, which is causing some confusion.
Wiki has a nice opening section, with the definition: "A prediction is a
statement or claim that a particular event will occur in the future in more
certain terms than a forecast. The etymology of this word is Latin (from
præ- "before" plus dicere "to say").", and I had in mind the idea of
predicting the future, not confirming the past -- as Niels Bohr said,
"Prediction is very difficult, especially if it's about the future.". I thus
pointed out that astronomy is not very good at predicting the future,
although of course it predicts the results of experiments to see what has
already happened. A lot depends on whether we consider making testable
statements about events as long ago as 12 billion years counts as
prediction! So if we drop the distinction between prediction and
confirmation, I don't think that there is any real dispute going on.
In terms of the initial discussion about theory vs. experiment, I was just
reminded of the "discovery" of the neutrino. Theorists claim that
mass-energy and momentum are conserved, but in beta decay, where a nucleus
emits an electron, this is not the case experimentally. So did the theorists
throw out the theory? Heavens no, they simply said that there was some other
undetectable particle emitted during the decay process that ran off with the
missing energy and momentum. Talk about fudging your results! It took 26
years for anyone to actually claim to detect a neutrino, but that did not
seem to bother physicists. Wirt just posted a decription of WIMPs, more
mysterious material whose existence is postulated simply because
experimental results conflict with theory.
Although this physics stuff may seem a trifle esoteric, the same situation
can occur in ecology. I remember once participating at a workshop to study
the ecosystem of a bay where I noticed that the measured secondary
production was higher than primary production. When I suggested that we
needed to calculate the flux of plankton into the bay I had problems
convincing my colleagues that the problem was that something was missing
from the experimental study, and not that we should jettison the idea of
conservation of energy (and there are ecologists who claim that living
organisms do not necessarily have to obey the law of conservation of
energy).
Another case which has never been fully resolved had to do with toxin uptake
by shellfish. In some cases if I take all the experimental data and
calculate the toxin load I cannot generate levels as high as are observed.
When I try to convince the experimentalists that some of the measurements
must be wrong, they insist that the fault must lie with the theory -- but no
one has ever come up with a theory that explains how shellfish can
accumulate more toxin than they ingest (and the experiments rule out
biotransformation).
Bill Silvert
- Re: [ECOLOG-L] Predictive science William Silvert
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