To Rick, Andrea, Elephant, and all,
Newton's law of gravity is F = G Ma Mb / r^2
In a technical sense the law of gravity was invented in 1686.
This is the sense it has when you consider the mathematical
equation and the number of newtons it calculates when you plug
in numbers for kilograms, meters, and the gravitational constant.
>From a human perspective its a new tool for predicting celestial
events and landing men on the moon.
But it's not so straight-forward as this. 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. When gravity pulls apples
and stars and planets and whole galaxies around, it uses this law
(or something very close to it) to decide how much pull to give
them. The fact that we observe elliptical galaxies and binary
stars thousands of light years away strongly suggests that the
law of gravity described by Newton was in force long before Newton
lived.
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. When you weigh
yourself on a scale, that is quantitative evidence. If you weigh
yourself in an airplane travelling at 40,000 ft, you'll weigh a
little less. In outer space you will be effectively weightless.
The proposal that the force equation for gravity is a definition
is misleading. Definitions serve to describe standards and
conventions and they convey a precise meaning in a lingual
shorthand. They don't say anything about how nature works. For
example, a meter is a definition whose sole purpose is to set a
standard for a unit of measure applied to space. The actual length
of a meter is completely arbitrary. It doesn't say anything about
how space works. The same is true for units of mass and units of
time. Examples of true axioms of nature are space, time, and mass
but *before* we've applied any units to them. The force equation
for gravity above shows that it is derivative of these other
axioms of nature and the principle it conveys is independent of
the particular units we choose. It says something quite
extraordinary about the way nature works and the way it worked at
least thousands of years ago. It says the force a massive body
exerts on another massive body is proportional to the masses of the
bodies and inversely proportional to the square of the distance
between them. This is the law in its idealized sense. There is no
math here until you apply numbers, and there can be no numbers
until you apply units.
Of course the force of gravity is not the only force. When you are
walking around an amusement park and your chum gives you a friendly
shove, you experience a force on your upper arm. Your friend is
responsible for imparting this force. When you ride the
Tilt-a-Whirl, you feel a force against your side as you are slinged
around. The Tilt-a-Whirl apparatus is responsible for imparting
this force. When we walk between amusements, we feel a force on the
bottoms of our feet. It is natural to assume that something is
responsible for imparting this force also, even though we cannot
see it with our eyes. We call it gravity, but obviously this is not
the same as the law of gravity. While certain proposed models for
gravity, such as the gravitational field and gravitons, have
reified gravity as those things to a certain extent, it's hard to
comprehend how the law of gravity reified gravity when you can
plainly experience that force yourself.
Before Newton people also experienced this qualitative force on
their feet. It was explained that man was imperfect and destined
to be stuck to the imperfect earth. When things of the earth were
tossed into the air, they came back to earth because they sought
their rightful place on earth, being made of the earth. The moon
didn't fall to earth because it was not of the earth, and its
motion was explained by its being attached and turned along a
concentric shell by an unseen god that existed outside the shell.
So far none of this is radical. It's just a general description of
what people believed in those days. The standard interpretation
today is that these beliefs were wrong and based on ignorance and
folks like Copernicus and Newton set the record straight when they
discovered how the heavens really operate.
The radical parts of Pirsig's belief are the consequences of saying
Newton's law was created and not discovered. This means Newton's law
was *not in effect* during the time of Ptolemeic belief in concentric
shells or at any time before that. And neither was gravity. What kept
people glued to the ground in Ptolemeic times were their beliefs for
why they should be stuck to the ground, and nothing more. Remember
that Pirsig says our concepts create our "so-called" reality, (true
reality is dynamic and flowing) not the other way round. Pirsig
doesn't believe nature exists independently of human thought - nature
is created as new beliefs are invented about nature - nature itself
is just in our heads. And I disagree.
I disagree because scientific historical evidence, such as the shape
of ancient galaxies and the age of rocks on earth, contradict his
belief. If you insist on holding fast to this way of thinking in the
face of this evidence, you end up saying things like:
- spiral galaxies are themselves beliefs concocted to further the
cultural illusion that Newton's theory is correct or
- spiral galaxies are themselves beliefs concocted to further the
illusion that things were discovered or
- old rocks are beliefs that support the notions of time and history,
which are also just human beliefs.
It strikes me that clinging to such beliefs will cause one to think
that a) everything we think we know is a conspiratorial brainwash
and b) time is not real and everything exists in the eternal present.
Since this is similar to Zen Bhuddism, Hinduism and mysticism, we
run to these things. Then, of course, we get shocked back into
reality when our spiritual teacher tells us the A-bomb dropped on
Hiroshima wasn't real. Folks like Pirsig end up having their beliefs
settle down in a half-way house between acceptance and denial of
objective reality, and once you realize this you begin to understand
why the principles underlying the MOQ are so schizophrenic.
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