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 civilisations to our existence. Of course, we don't know if such civilisations 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 civilisations out there that might otherwise be staying quiet.