In 2006, NASA stumbled across a source of radio waves with six times the intensity of any other source ever measured. In fact, alone it produced a more intense radio signal than all the stars and galaxies in the entire universe put together. So what the hell was it?

Now known as The Space Roar, the radio emissions remain somewhat of a mystery—but this video by Sci Show rounds up everything we known about it at the moment. Including why, oddly, we can't really hear it. [Sci Show]