Once again, it's time for David Feldman to plunge into that sea of question marks and conundrums known as Imponderables. These are the mysteries of everyday life. They're the questions that can't be answered by numbers, measurements, or a trip to the reference library. They're the things that drive you nuts - or that you've never thought of until someone brings them up, and then they drive you nuts. Don't you ever wonder, for instance, how astronauts scratch an itch? Or. Why blank videocassettes slide out of the backs of their boxes, while prerecorded tapes fall out of the bottom? How do skywriters learn good penmanship? From the thousands of letters, phone calls and E-mail messages he gets every year, Feldman has picked the most intriguing puzzles and gone to the experts to find the answers. In his light, bright, delightful style, he tells us not only the how and the why, but the who, what, where and when.