One of the unfortunate parts of our being the only intelligent species we know of is that while we can mathematically guesstimate life's appearance throughout t

One of the unfortunate parts of our being the only intelligent species we know of is that while we can mathematically guesstimate life's appearance throughout the cosmos, we have no data on when intelligent civilizations die out. In the final episode of Cosmos, Carl Sagan describes a nightmare in which he is traveling the universe and decides to return to earth. As he gets closer, his spaceship intercepts broadcasts that have been traversing space since the invention of radio, from the earliest radio messages to television signals and then eventually...the signals stop.