One of the most common questions asked of writers at science fiction conventions is: “What are your favorite pieces of science fiction?” I usually name two or three, but they tend to change even from day to day. I’m asking myself that question now. And my answers, for this afternoon, are: “The Million-Year Picnic,” by Ray Bradbury; “Rattlesnake Men,” by Michael Bishop; “Nightfall,” by Isaac Asimov; “The Green Hills of Earth,” by Robert Heinlein; “First Contact,” by Murray Leinster; and “The Star,” by Arthur Clarke. Ask for a few more, and I’m thinking about it: Maybe “The Cold Equations,” by Tom Godwin. And Frankenstein, by Mary Shelley; “Flowers for Algernon,” by Daniel Keyes; “Immortality"