文档介绍：Foundations
by Greg Egan
4: Quantum Mechanics
Copyright © Greg Egan, 1999. All rights reserved.
The first three articles in this series dealt with special and general relativity, the two great
twentieth-century theories of the geometry of spacetime and its relationship with matter
and energy. This article will describe the ideas behind a second, simultaneous revolution
in physics, one that has had even more profound philosophical and technological
consequences: quantum mechanics.
The Birth of Quantum Mechanics
In the second half of the eenth century, the Newtonian description of the dynamics
of material objects was supplemented by an equally essful theory passing all
of electrostatics, ism and optics. The physicist James Clerk Maxwell brought
together a number of disparate laws that had been found to govern quite specific
phenomena — such as the force between two motionless electric charges — into a unified
description of an ic field. Light, and most other forms of radiation,
were seen to consist of oscillations in this field, or ic waves. This
confirmation of the wave-like nature of light made sense of many long-standing
observations, including the phenomenon of interference: if you allow light of a single
wavelength to travel through two adjacent narrow slits in a barrier and then bine on
a screen, it produces patterns of dark and light stripes. Since the difference in the time it
takes for light waves from the two slits to reach the screen varies from place to place, the
waves shift in and out of phase with each other, resulting in varying degrees of
constructive interference (where the contributions to the field from both slits point in the
same direction), and destructive interference (where they point in opposite directions).
Egan: "Foundations 4"/
Newtonian dynamics and Maxwellian electrodynamics cut a wide swath through
the scientific problems of the day. However, by the end of the eenth century a
numbe