Sheree R. Thomas, the editor of Dark Matter, subtitled the anthology A Century of Speculative Fiction From the African Diaspora. Don’t be alarmed by the unfamiliar term. Speculative fiction is to science fiction what black is to African-American: often interchangeable, but a little broader. And, in this case, more appropriate, given that black writers have a short history in traditional sci-fi. In his essay “Black to the Future,” one of the book’s few nonfiction pieces, Walter Mosley suggests that black folks have long been able to fantasize about themselves only in positions of “powerlessness,” “ignorance,” or “servitude,” if at all. We’re just starting to appreciate our impact on the past and present, much less our possible role in the future. So “speculative” has just the right tone for a collection that, in relatively few steps, covers the considerable distance between really seeing blacks on Earth and, say, seeing us in space. Thomas reads from and discusses Dark Matter at 4 p.m. at Sisterspace and Books, 1515 U St. NW. Free. (202) 332-3433. (Neil Drumming)