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Re: [HM] Galileo
Posted:
Mar 24, 2004 2:54 PM
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At 12:01 PM 3/24/04, William Tait wrote:
[deletion]
<< Preceding this is a discussion of failures to reproduce the `inclined
plane experiment', the reasons for failure, and the likelihood of
Galileo having arrived at his formula for frictionless motion down an
inclined plane by experiment---or perhaps one should say entirely by
experiment. [Surely he had some experimental grounds for rejecting
Aristotle and believing that free fall did not depend upon the weight
of the object, for example.] >>
I note that one of the main points of the work of Alexander Koyre on
Galileo's work was that Galileo had arrived at his results on falling
bodies on theoretical grounds, and that the experiments were intended
to verify (or test?) his results. As I recall it, Galileo used a kind of
proto-calculus technique involving moving from constant acceleration
to the law of falling bodies using some simple geometrical arguments.
Koyre was in part reacting against popular beliefs, especially put
forth in the 19th century by various historians and others which
put emphasis on experimentation as a method of discovery, in the
tradition allegedly instituted or greatly encouraged by Francis Bacon.
This sort of thing was, for example, found in elementary physics textbooks
until comparatively recently, say until some time after World War 2,
when history of science flourished in various places in the world.
If I remember correctly, there was a counter-revolutionary move by, I
think, Stillman Drake, who challenged the extent to which Galileo
worked with theoretical _thought_ experiments and theoretical
deductions from proposed axioms, such as that the acceleration
of gravity (near the surface of the earth) is constant. The debate
hinges, it appears, on differences between discovery by observation
and discovery by deductions from proposed postulates. Of course,
proposed postulates are customarily somehow suggested by
observations, but on the other hand, it may be that no actual
observational measurements may be made _before_ a discovery of
a postulate is made which turns out to be a good one.
This debate, as no doubt many on the list know, has been a
much investigated topic by philosophers of science and other
interested parties for many years. Which comes first, the
egg of discovery or the chicken of experiment? Or are the
two so interactively related that strict separation of them will
only lead to sterile abstractions?
Gordon Fisher
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