Wednesday marks the 75^th anniversary of Orson Welles’ electrifying War of the Worlds broadcast, in which the Mercury Theatre on the Air enacted a Martian invasion of Earth. “Upwards of a million people, [were] convinced, if only briefly, that the United States was being laid waste by alien invaders,” narrator Oliver Platt informs us in the new PBS documentary commemorating the program. The panic inspired by Welles made War of the Worlds perhaps the most notorious event in American broadcast history...