In 1974 a message was beamed towards the stars by the giant Arecibo telescope in Puerto Rico, a brief blast of radio waves designed to alert extraterrestrial civilizations to our existence.
Of course, we don't know if such civilizations really exist. For the past six decades a small cadre of researchers have been on a quest to find out, as part of SETI, the search for extraterrestrial intelligence. So far, SETI has found no evidence of extraterrestrial life, but with more than a hundred billion stars in our Galaxy alone to search, the odds of quick success are stacked against us.
The silence from the stars is prompting some researchers, inspired by the Arecibo transmission, to transmit more messages into space, in an effort to provoke a response from any civilizations out there that might otherwise be staying quiet. However, the act of transmitting raises troubling questions about the process of contact. We look for qualities such as altruism and intelligence in extraterrestrial life, but what do these mean to humankind? Can civilizations survive in the Universe long enough for us to detect them, and what can their existence, or lack thereof, reveal to us about our future prospects? Can we learn something about our own history when we explore what happens when two civilizations come into contact? Finally, do the answers tell us that it is safe to transmit, even though we know nothing about extraterrestrial life, or as Stephen Hawking argued, are we placing humanity in jeopardy by doing so?