"Soon after atomic bombs exploded over Hiroshima and Nagasaki in 1945, MGM set out to make a movie studio chief Louis B. Mayer called "the most important story" he would ever film: a big budget dramatization of the Manhattan Project and the invention and use of the revolutionary new weapon. Over at Paramount, Hal B. Wallis was ramping up his own film version. His screenwriter: the novelist Ayn Rand, who saw in physicist J. Robert Oppenheimer the model...