(Vox) - Radio signals from deep space — and a controversial interview by a Harvard astrophysicist — have people wondering, once again, whether or not we’re alone in the universe. A new investigation published in Nature looked into fast radio bursts, an astronomical mystery that some have argued might be artificial in origin. We detected the first fast radio bursts in 2007, but new technology has allowed us to detect many more of them, and confirm that some repeat themselves. The origin of these repeating signals is unknown, leading some scientists to speculate aliens could be sending them.