On Halloween night 1938, Orson Welles broadcast a radio adaptation of the H. G. Wells fantasy, The War of the Worlds. What listeners heard sounded so realistic that at least a million were frightened by word that "strange creatures" from Mars had landed in central New Jersey and were "unleashing a deadly assault." Several thousand were so terrified they ran into the streets, drove away in their cars, or called the police for information about how...