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David, Just kinda jumping in here, regarding “inertial”
and “gravitational”. This refers to the dualistic properties of a
thing (such as a particle) as being something which can be pushed, and as being
something which can push something else, respectively. In state-based physics
this dualism is codified in the system/environment dualism. A system S (such as
a particle) has assigned to it a position and the first derivative of position (i.e.,
velocity). But the second derivative, acceleration, is represented by F=ma, so that a=F/m. But F, force, is not part of the system S; instead, F comes
from elsewhere – it is impressed
on S from the environment. This dualism has served us well for the most
part, allowing a great deal of physics to be done. However, when a system (rather than a system and its environment)
involves both inertial and gravitational aspects simultaneously, we find the
limits of this approach. Thus, on EL p. 109: “But
even here, this stops being true once we try to interpret, or realize, Newtonian impressed forces as arising
from the gravitation of other particles; that is, as soon as we put our
particle into a bigger system of particles. Roughly, when we do this, we are
allowing that impressed force to be determined (at least in part) by the
particle itself. The particle is now (phenotypically) behaving in a “field
of force” that it participates in generating. Although a classical
particle is forbidden from (gravitationally) pushing itself when it is alone,
adding other particles allows it to push things that can push it. The resultant
impredicativities, which in fact plague all field theories of particle-based
forces, arise as soon as we try to identify inertia (phenotype) with
gravitation (genotype) independent of any larger context. This
is why, for instance one cannot solve a three-body problem reductionistically,
by solving two-body and one-body problems.”[ital. orig.] If one pictures a 3-body system, and the set
of state-based equations involved, they requires that one body be considered an
inertial system being forced by the other two (gravitational) bodies. So we
have drawn a box, as it were, around the first body and said: this is the
system, all else (namely, the two other bodies) is the environment of the
system. A very tractable problem. But then, this division into system and
environment must be repeated for the other two bodies in turn, and all the
equations must be solved simultaneously. So each body is acting as a thing which can
be forced and also a thing which can force something else; but additionally,
the things which it can force (i.e., the other two bodies) can force it. So we end up with the
impredicativities as Rosen described. Its not that the state-based equations
are wrong, but they are limited in what aspects they can model about the three-body
system. And if we break the system apart reductionistically, then we lose the relationship of a body pushing on other
bodies which push on it. To model these impredicative relationships requires a
non-state-based model. Such a model will describe the relationships between those
simultaneous forcings, and those forcings are of course in the category of efficient
cause, thus in your quote from Rosen: “This can be expressed as a shift
from concerns with material causations of behavior, manifested in state sets,
to formal and efficient causations.” The inertial/gravitational distinction also
shows up with the (M,R)-system model, which is concerned with relationships
between efficient causes, rather than with the material causes (the molecules,
etc.) being forced. Regards, Tim From: ROSEN Forum
[mailto:*** On Behalf
Of David Macy -snip- In Robert Rosen's book Essays on Life Itself in
chapter one there is a section entitled: What is this "New
Physics"? In it Robert says the following... Most significant, I feel,
will be the shifting of attention from exclusively inertial (or structural)
concepts to gravitational aspects. This can be expressed as a shift from
concerns with material causations of behavior, manifested in state sets, to
formal and effecient causations. So I was just trying to get a jump on things, if you
know what I mean. I am still not clear about how RR uses the terms
inertial and gravitational. He seems to be talking to physicists when he
uses these terms, and I'm not a physicist. -snip- |