In a few months, NASA scientists and the press will note the passing of the 30th anniversary since the launches of Voyagers I and II. By now, both interstellar probes have passed beyond Pluto's orbit and are speeding out toward neighboring star systems, carrying with them copies of the Golden Record, a phonograph record full of images, music and recordings of life on Earth intended for any extraterrestrials who might happen upon the probe and wonder who sent it. It's the same idea behind the plaque that was bolted onto the Pioneer 10 and 11 spacecraft, both of which are currently gliding out of the solar system behind the Voyager probes.