If you're a Douglas Adams fan, then you know of his oft-maligned fifth entry in the "Hitchhiker's Guide to the Galaxy" series, "Mostly Harmless." In that book, a fictional 10th (which would be 9th, had Mr. Adams been writing after 2006, which wouldn't that have been wonderful?) planet lurks in the dark outer reaches of our solar system. From the icy surface of that dim world aliens observe Earth's radio and television broadcasts that have leaked out into space. To find out what happens next, you'll have to read the book (sometimes I can be a wee bit the sadist).
According to astronomers with much better math skills and much faster computers than I, the math seems to be working out again that there's another planet out there in the far reaches of ol' Sol's gravitational influence. Reading this made me think some things:
An often meandering repository for SciFi Author and Occasional Poet Robert C. Murray.