If the space-telephone rings, should we answer? Astronomer John Macvey, quoting Zdenik Kopal of the University of Manchester, says maybe not. In this cautious, somewhat wistful survey of space travel past, present, and future, the author dismisses much of UFOlogy as nonsense but comes out strongly in support of some happenings as the real thing. If so, then these Aliens might be idly curious at best, dealing with us as we might deal with ants to be sampled and studied in the lab. Or, if they need Lebensraum, they might be openly hostile--hence caution in answering the phone. The book opens with some good nontechnical explanations of how space travel might be accomplished, either by achieving speeds close to the speed of light or by the more non-orthodox methods of descent into black holes, cuts across space into ""non-space,"" and other space warp techniques. There is also some reasonable discussion of the biochemistry one might expect on other habitable worlds (giving the lie to the classic cliches of either noble Aryan types or ""BEM's""--bug-eyed monsters). But then the book wanders off into speculations and sightings, including the author's own experiences. Here the wish to believe and persuade exceeds plausibility and the reader's patience.