Note to self: Do not rely on memory for sci-fi facts. A legion of readers have told me, some adding a garnish of withering scorn, that the story I remembered is not by Robert Silverberg at all. It is “Eutopia,” by Poul Anderson, and appears in the collection “Dangerous Visions” by Harlan Ellison. I am sorry. Sorry sorry sorry sorry sorry…

(I note, by the way, that “So long, and thanks for all the fish!” translates into Hungarian as: “Viszlát, és kösz a halakat!” These are the things you learn when googling.)