Hi all,
This is mostly to Glenn, Dan Dunn and elephant, but also to whoever else
is involved in the discussion.
(Elephant, you may want to follow-up on my concluding comments about
empiricism).
Well we've certainly got a lot of mileage out of this gravity
discussion. There are many contrasting and conflicting viewpoints, and
it seems that everyone is right in their own way!
I especially want to than Dan Dunn for his elegantly simple explanation
of gravity according to Einstein.
What motivates me to write now is Glenn's very revealing latest post:
GLENN
> In a technical sense the law of gravity was invented in 1686.
[snip]
>Nature herself seems
> to have "known" this law long before Newton did, not as
> mathematical terminology, not as a maggot inscribing the formula
> in an apple, but in an idealized sense.
This sounds backwards to me. It's like that T-shirt the physicists like
to wear, which bears the word "And God said . . ." followed by the
Maxwell equations, and finally "And there was light . . ."
I hope Glenn does not intend to ascribe the physical phenomena we call
gravity and light as CONSEQUENCES of the various equations or causal
mechanisms the physicists have come up with! I certainly don't reject
the idea of explaining natural phenomena mechanistically, but we should
always remember to include the words "AS IF" (I note that Donny used to
advise adding "as if" to philosophical statements as well).
Nature acts AS IF it were following Newton's law of gravity. Thus,
should we observe a discrepancy, it must be attributed to incorrectness
of the mechanistic explanation, not a failure of nature. Pirsig's
platypus story was to illustrate the same point - the platypus
was no freak of nature; it was the zoologists who had gotten it wrong!
GLENN
> My previous agreement with Andrea about gravity not being empirical
> was incorrect. The feeling of force on your feet when you stand up
> is qualitative empirical evidence of gravity.
Think again Glenn. In which direction does the force act on your feet?
You feel a force UPWARDS, i.e. AGAINST the direction of gravity. You
don't ever feel the downward gravitational force itself. Your claim that
such a force exists is a conjecture and certainly not an empirical
observation. Einstein threw out some of the assumptions that lead to
that conjecture, and thus came up with a gravitational theory that does
not involve a force.
I note that elephant takes an ANTI-empiricism approach, and admit that
Glenn's mistaken "empirical evidence" for gravitational force raises an
interesting question: What constitutes primary empirical evidence? Does
such a thing exist, or is it an unattainable ideal? (That's an ironic
twist on the idealism vs. empiricism argument).
Jonathan
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