On April 30, 1939, under the gathering storm clouds of war, the New York World’s Fair opened in Flushing Meadows, Queens. Its theme was The World of Tomorrow. ... Some of the displayed innovations were truly visionary. ... Albert Einstein, honorary chair of the fair’s science advisory committee, ... spoke to a huge crowd on the topic of cosmic rays, highly energetic subatomic particles bombarding the Earth from outer space. But two scientific discoveries that would soon dominate the world were absent at the fair: nuclear energy and electronic...