1905, and then with his general theory of relativity a decade later. When ini-
tially propounded, these theories had seemed primarily of scholarly interest,
as Einstein was rethinking the nature of space, time, gravity, and other fun-
damental forces of the universe. But various implications of his work proved
to be of the utmost practical consequence, as Einstein himself came to real-
ize. In a 1939 letter to President Roosevelt, he called attention to the possi-
bility that extremely powerful bombs might be constructed if one could set
off nuclear chain reactions in a mass of uranium: Einstein's message proved
a crucial factor in the authorization of work on nuclear weapons. By the end
of 1943, work in Los Alamos, New Mexico, on the development of an atomic
bomb had advanced to a crucial point; this work would have been incon-
ceivable in the absence of Einstein's revolutionary insights about the rela-
tionship between matter and energy.

When we think of leaders, we usually envision the political or military
giants of an era--Alexander the Great, Napoléon Bonaparte, Abraham
Lincoln, or the generals of the Civil War. The familiar photograph of Stalin,
Roosevelt, and Churchill seated alongside one another on a veranda in
Tehran epitomizes this common conception of what leaders look like, even

The leaders of the Allies at Tehran, 1943: (seated left to right) Stalin, Roosevelt, Churchill.

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