On Dec. 18, the world learned that Breakthrough Listen, a privately funded search for extraterrestrial intelligence, had found its first official candidate signal. The signal’s existence lit up the Internet. Was BLC-1, as it’s called, finally our moment of contact? Breakthrough Listen scientists, now hard at work on a paper about their findings, were quick to explain that the answer was probably “no”: Given the wealth of human-made radio signal interference out there, BLC-1 will probably turn out to be of human origin.