Just as medicine is not a science, but rather an art – a device, practiced in a scientific manner, in its best manifestations – time-travel stories, some would argue, are not science fiction. But whether they are or aren’t, time-travel has become acceptable to science fiction readers as a traditional device in stories some might call admissible in the genre. Here, Frederik Pohl employs it to portray the amusingly catastrophic meeting of three societies.