For decades we've been sending signals - deliberate and accidental - into space. But what is the plan if one day an alien were to reply?
If we ever detect signs of intelligent alien life, the people likely to be on the receiving end of a cosmic signal are the scientists of Seti, aka Search for Extraterrestrial Intelligence.
This loose band of a couple of dozen researchers around the world doggedly listens to the cosmos in the hopes of catching alien communications. It's often in the face of scant funding and even ridicule.
They watch signals coming from the world's largest radio telescopes, looking for anything unusual, or even the flashes of laser "lighthouses" designed to catch our attention.
Seti started as one man using one telescope dish in 1959. Today computers are used to sift through the cosmic radio traffic, flagging up to astronomers any potential calls from extraterrestrial life.
But what might happen if one of those computers found a bona fide alien phone call?
They're likely to be hung up on. ;-) To read more, click here.