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Re: Causation in Physics: F=ma



This causation thread provokes me to utter the following random thoughts:

Just yesterday, while introducing magnetic force I asked the class if
any of them were bothered by the idea that the magnetic force could
be determined by the velocity of the charged object. One student
responded that it did seem odd because we expect forces to depend on
the acceleration of an object.

I appreciate the point that one should not get too hung up on
interpreting physics equations in terms of cause and effect; they are
at some level nothing more than relationships that must be satisfied.
Nevertheless, I will go boldly on record as saying that I am far more
comfortable with the idea that forces cause acceleration than vice
versa and that includes situations covered by the equivalence
principle. But I would need an alternate verb to describe the role
of mass in Newton's second law. My gut tells me that it is neither
the "cause" nor the "effect" of either force or acceleration. Its
role seems more properly passive and parametric.

It is entertaining to read some of the links that show up for this search

<http://www.google.com/search?q=cause-and-effect+logic>

Some authors maintain that to establish a cause and effect
relationship, the cause must precede the effect. It seems to me that
very few if any fundamental physical relationships are expressed in
ways that explicitly incorporate such a time delay. But would anyone
argue that "cause and effect" is nothing more than an illusion?

--
John Mallinckrodt mailto:ajm@csupomona.edu
Cal Poly Pomona http://www.csupomona.edu/~ajm