  This paper explores the possibility that asset prices, especially those
traded in large volume on public exchanges, might comply with specific physical
laws of motion and probability. The paper first examines the basic dynamics of
asset price displacement and finds one can model this dynamic as a harmonic
oscillator at local "slices" of elapsed time. Based on this finding, the paper
theorizes that price displacements are constrained, meaning they have extreme
values beyond which they cannot go when measured over a large number of
sequential periods. By assuming price displacements are also subject to the
principle of stationary action, the paper explores a method for measuring
specific probabilities of future price displacements based on prior historical
data. Testing this theory with two prevalent stock indices suggests it can make
accurate forecasts as to constraints on extreme price movements during market
"crashes" and probabilities of specific price displacements at other times.
