If you've read your share of sci-fi, and I know you have, you've read stories about another Earth-sized planet orbiting on the other side of the Solar System, blocked by the Sun. Could it really be there? =========================================================== Color illustration showing the scale of planets in our solar system, focusing on Jupiter and Saturn. Credit: NASA =========================================================== No. Nooooo. No. Just no. This is a delightful staple in science fiction. There's a mysterious world that orbits the Sun exactly the same distance as Earth, but it's directly across the Solar System from us; always hidden by the Sun. Little do...