At speeds close to the speed
of light in vacuum c relativistic effects become
important to consider. Such speeds are normally not encountered
in everyday life. However, special relativity is used by
scientists when doing calculations in, e.g., particle kinematics,
since the particles often have speeds close to the speed
of light in vacuum. Also in space physics, special relativity
is an important tool.
In 1928, the brilliant English physicist P.A.M. Dirac
unified the quantum theory of W. Heisenberg with special
relativity in two papers named "The Quantum Theory of
the Electron." He received the Nobel Prize in Physics
for his contribution as early as 1933. He shared the prize
with the Austrian physicist E. Schrödringer, who
played a major role in the development of quantum mechanics.
At a conference dedicated to the one-hundredth anniversary
of Einstein's birth, Dirac said: "Right from the beginning
of quantum mechanics, I was very much concerned with the
problem of fitting it in with relativity. This turned
out to be very difficult, except in the case of a single
particle, where it was possible to make some progress.
One could find equations for describing a single particle
in accordance with quantum mechanics, in agreement with
the principle of special relativity. It turned out that
this provided an explanation of the spin of the electron." The
equation that Dirac was talking about is today known as
the Dirac equation and this is the equation describing
the dynamics of particles with spin 1/2. Furthermore,
Dirac said: " Also, one could develop the theory a little
further and get to the idea of antimatter. The idea of
antimatter really follows directly from Einstein's special
theory of relativity when it is combined with the quantum
mechanics of Heisenberg. There is no escape from it."