246
EVERY PARTICLE OF
MATTER HAS AN
ANTIMATTER
COUNTERPART
PAUL DIRAC (1902–1984)
IN CONTEXT
BRANCH
PhysicsBEFORE
1925 Werner Heisenberg,
Max Born, and Pascual Jordan
develop matrix mechanics
to describe the wavelike
behavior of particles.1926 Erwin Schrödinger
develops a wave function
describing the change in
an electron over time.AFTER
1932 The existence of the
positron, the antiparticle to
the electron, is confirmed by
Carl Anderson.1940s Richard Feynman,
Sin-Itiro Tomonaga, and
Julian Schwinger develop
quantum electrodynamics—
a mathematical way to
describe the interaction
between light and matter,
which fully unites quantum
theory with special relativity.E
nglish physicist Paul Dirac
contributed a huge amount
to the theoretical framework
of quantum physics in the 1920s,
but is probably best known today
for predicting the existence of
antiparticles through mathematics.
Dirac was a postgraduate
student at Cambridge University
when he read Werner Heisenberg’s
groundbreaking paper on matrix
mechanics, which described how
particles jump from one quantum
state to another. Dirac was one
of the few people capable of grasping
the paper’s difficult mathematics,
and noticed parallels between
Heisenberg’s equations and parts
of the classical (pre-quantum)
theory of particle motion known
as Hamiltonian mechanics. This
allowed Dirac to develop a method
by which classical systems could
be understood on a quantum level.
One early result of this work
was a derivation of the idea of
quantum spin. Dirac formulated a
set of rules now known as “Fermi-
Dirac statistics” (since they were
also independently found by Enrico
Fermi). Dirac named particles such
as electrons that have a half-integer
spin value “fermions,” after Fermi.
The rules describe how largeAntimatter is
subsequently discovered,
confirming Dirac’s prediction.Every particle
of matter has
an antimatter
counterpart.Dirac corrects
Schrödinger’s wave
equation to take into account
relativistic effects.Dirac’s new equation
predicts the existence
of antimatter.