In the three decades prior to his death, Einstein's distrust
of quantum theory isolated him from the mainstream developments
in physics. All of his greatest contributions to science had been
made by 1926, and from this point on, he remained a staunch opponent of
the theory he had done so much to build in his earlier years.
Einstein focused his efforts instead on developing a unified field
theory, a theory which would explain both gravity and electromagnetism
in one principled mathematical account. He hoped to resolve the
conflict between the smooth continuum of space-time described by
his general theory of relativity, and the jittery submicroscopic
particle-world where quantum theory reigns. Although he never
succeeded in this endeavor, in a sense he was simply ahead of his
time: throughout the 1980s and 1990s, the primary goal of theoretical physicists
has been the formulation of a grand theory of everything, or TOE,
that would account for every element of physical reality.