From Bob Clark (931119.1645 EST)
Bill Powers (931118.0630 MST)
A principle like conservation of energy (to pick a neutral example)
is not the explanation of why a pendulum works as it does. It is a
consequence of the way the pendulum works; it is a more generalized
way of perceiving the workings of a pendulum. It is of course, a
very useful principle. But it has no causal properties beyond those
given to it by a purposive system.
Of course I agree that it is a "very useful principle," and "it has
no causal properties, etc" My concern regards the nature of
"conservation of energy" and related concepts from physics.
I regard Newton's "Laws" as "descriptions" couched in a mathematical
form, rather than an "explanation" of a portion of the workings of
the physical world. Because these Laws can be used to derive many
useful mathematical expressions, considerable ingenuity has sometimes
been used for their preservation.
Note:
1) F = M * a
F and a can be measured independently of 1), but M cannot. 1)
amounts to an arbitrary definition of M. When this expression
doesn't fit the experiment, additional forces are "invented" to
maintain the utility of 1). Deviation from the Pisa experiment are
accounted for by air resistance. Sliding on an inclined plane uses
"force of friction." Electrostatic and magnetic forces are added as
needed. These are all very useful and appropriate, but logically
they remain no more than "descriptions" -- complex, perhaps, but no
more.
"Energy" and other expressions are readily derived from 1) by
suitable mathematical manipulations and definitions of forms.
"Conservation," originally applied separately to both "mass" and
"energy." Special Relativity, another mathematical descriptive
structure, resulted in their combination into "Conservation of
Energy." "Momentum," both linear and angular are also "conserved." If
they are not, major revisions are required in large parts of modern
physics. But they remain, logically speaking, at the level of useful
assumptions for the quantitative description of the physical world.
Interestingly, at one point, the late 20's I think, when beta rays
were being studied, the conservation laws were questioned. Energy
conservation required accounting for all energies observed. This was
ok until it was pointed out that beta ray spectra are continuous
rather than linear. Energy was not accounted for! The problem was
solved by the invention of neutrinos.
Such assumptions and inventions are not uncommon in the history of
physics.
I hope this short dissertation is useful to those on the net.
Regards, Bob Clark