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Re: [ontolog-forum] History of the Atomic Hypothesis

To: "[ontolog-forum]" <ontolog-forum@xxxxxxxxxxxxxxxx>
From: "John F. Sowa" <sowa@xxxxxxxxxxx>
Date: Tue, 05 Aug 2008 03:08:51 -0400
Message-id: <4897FC83.9020406@xxxxxxxxxxx>
Alex,    (01)

I changed the subject line back to the original to preserve the
continuity in the thread.  I would also like to repeat the original
reason for this topic:  the purpose is not to give anyone a history
lesson about atoms, but to illustrate the way definitions change
over time.  Almost any term we find in the dictionary could show
that.  I chose 'atom' because it illustrates how meanings change
while the words remain constant:    (02)

  1. The word 'atomos' in Greek to 'atom' in English has remained
     unchanged for nearly 2500 years.    (03)

  2. For most of that time, it was one of two reasonable hypotheses,
     and there was little or no evidence for choosing between them.    (04)

  3. When some evidence began to accumulate, it did not come from
     physics, but from chemistry.  The chemists formulated their
     theories in terms of atoms a century before the physicists.    (05)

  4. By the time the physicists became convinced that the hypothesis
     was true, they began to discover that those so-called atoms,
     were actually divisible into smaller particles.    (06)

  5. As more and more evidence accumulated, the nature of atoms
     seemed stranger and stranger.  Instead of being solid particles,
     they looked like systems composed of multiple wave-like fields.    (07)

  6. Yet the mathematics that governed those strange little systems
     accurately predicted the old measurements made by the chemists.    (08)

 > And for me first definition now is "chemical" ("by nature";) -
 > first part in WT#3. So we have:
 > "The smallest possible amount of matter which still retains
 > its identity as a chemical element."
 > The second definition is from http://www.wro.org/ras/glossary/a-c.htm
 > "A particle made up of a central nucleus surrounded by electrons."
 > For me the second is from nucleus physics.    (09)

Yes, but the physicists started with the first definition.  When
electrons were discovered, it wasn't obvious whether they were part
of atoms.  Later, physicists invented many different hypotheses
about how electrons were combined with a positively charged nucleus:    (010)

  1. Plum pudding:  One guess was that the heavy part of an atom was
     a positively charged "pudding", and the electrons were like
     little raisins that oscillated inside the pudding in order to
     give off radiation at the observed frequencies.    (011)

  2. Solar system:  Niels Bohr made a guess that electrons orbited
     the nucleus like planets around the sun.    (012)

  3. Wave fields:  de Broglie guessed that electrons behaved like
     waves in the same way as photons of light. Schrödinger's equation
     and later Dirac's equation made very accurate predictions about
     those waves and their interactions.    (013)

What we see is a series of more and more accurate models that are
better and better approximations to the observed measurements.  Some
of the definitions are consistent with one another, but many of the
definitions contradict the older ones.  We can never be sure whether
our current theories are "true" or just useful stepping stones toward
a completely different theory in the future.    (014)

Very often, scientists who firmly believe in the old theories make
the crucial discoveries that overturn them.  Tycho Brahe believed
in the Ptolemaic theory of the solar system, but his precise
measurements enabled Kepler, his assistant, to discover a totally
new theory that was more accurate than the one by Copernicus.
Priestley discovered oxygen, but he called it "dephlogisticated air".    (015)

 > So I am very optimistic about formalization of language of
 > "natural sciences"    (016)

I would agree that there is a lot that can be formalized in science,
but that is very different from formalizing the entire vocabulary
of English or any other natural language.    (017)

This discussion about atoms indicates that there isn't just one
theory, but a progression of theories with many disagreements along
the way.  Even worse, the equations are so difficult to solve in
general that scientists and engineers make many approximations
for special cases that are incompatible with one another.    (018)

For example, the equations of fluid mechanics are so difficult
to solve in general that every application uses a different set
of approximations:    (019)

    Supersonic fluid flow vs. subsonic flow; flow through pipes vs.
    flow across surfaces; turbulent vs. laminar flow; compressible
    fluid vs. incompressible; thermal convection, boiling, condensing,
    freezing; conducting fluids in electromagnetic fields; etc.    (020)

The approximations for one problem are based on assumptions that
may be false for another problem.  Sometimes a single problem
may have different aspects (e.g., an airplane that accelerates
from subsonic to supersonic flight) that require different and
inconsistent approximations for different parts or phases of the
same system.    (021)

John    (022)

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