Spring 2005 Physics Colloquium
March 11; Friday, PAS 220, 3pm
Larry Curtis
University of Toledo
"Probability Densities and Newton's Laws"
(Why didn't Newton think about the probability of getting hit on the head
when he sat under the apple tree?)
A significant distinction exists between the conceptual frameworks used in
introductory physics courses and in subsequent courses for physics
majors. Although the distinction is often characterized as "classical"
versus "quantum mechanical,'' the primary difference is not due to
quantization. Instead it is a nonessential heuristic tendency to describe
macroscopic systems by instantaneous values for position, speed, and
acceleration, and microscopic systems by time-averaged position probability
densities. This produces a serious disconnect between physics as it is
practiced, and as it is taught to non-physicists (and hence between physics
and society). Alternatives to this framework will be discussed involving a
simple, pedagogically transparent use of position probability densities
(and optional semiclassical quantization) to describe both macroscopic and
microscopic systems that we have used at the graduate, undergraduate, and
community outreach levels.