With science fiction, an activity one could do is to compare the predictions that came true to the predictions that haven’t happened yet (and, for that matter, technologies that actually came into existence but which were not anticipated in the past by science fiction.) In “When the Tripods Came,” the 1984 prequel to the Tripods trilogy by John Christopher, the author talks about science fiction predictions failing many more times often than successfully guessing future developments. (To be sure, there have been predictions that came out roughly accurate, such as H.G. Wells and the use of tanks in military warfare.) In fact, the prequel was written in part because a leading British science fiction author was doubtful of the trilogy’s premise, in which three-legged alien Tripod machines take control over most of humanity, and a small group of persons must work to free mankind. How could alien invaders that used searchlights (instead of infrared night-vision) be taken seriously by advanced civilization? (Among other things, the first of the books in the trilogy was written in the late 1960s, when infrared technology was mostly relegated to laboratories.)