Tom's theory of why human beings had yet to receive any message from extraterrestrial intelligences was that all civilizations, without exception, blew themselves up almost as soon as they were able to get a message out, never lasting more than a few decades in a galaxy whose age was billions; blinking in and out of existence so fast that, even if the galaxy abounded with earthlike planets, the chances of one civilization sticking around to get a message from another were vanishingly low, because it was too damned easy to split the atom.