Re: CAUSATION IN PHYSICS

[Joel Rauber <Joel_Rauber@SDSTATE.EDU>]

JC wrote in part:


> Since definitions are a good opportunity to demonstrate
> "smart" ideas, and
> to dump memorized ideas, I never ask for them.  Instead I ask them to
> describe how they know something.  "What evidence do you have
> that the body
> is accelerating?"



> Definitions are usually
> operational, rather than precisely stated.

It strikes me that the definition of v as being identical to dx/dt is a
precise mathematical statement (the most precise kinds of statements that I
know of).  I can only talk about operational definitions with confidence
(as
opposed to preliminary suggestions of things that may be important, as when
trying to come up with a good precise definition) by reference to the
precise above definition.  Namely, e.g. I knot that the object velocity is
changing because the strobe images of the object appear farther apart in
each interval implying from the definition of velocity that it is changing.

While I agree that how do you know questions are good, they implicitly
involve "What is the definition?"  type of a questions.  I don't rule out
definition questions myself, as it at least tells me if the student is
paying attention enough to know the specialized vocabularly we are
building.
Admittedly the the "how do you know" questions can serve the same function
in part, part there are other obscuring features to them.




Joel Rauber
Joel_Rauber@sdstate.edu