Earth emits an ear-piercing series of chirps and whistles that could be heard by any aliens who might be listening, if they're out there. The sound is awful, a new recording from space reveals. Scientists have known about the radiation since the 1970s. It is created high above the planet, where charged particles from the solar wind collide with Earth's magnetic field. • Click here to hear the sounds. It is related to the phenomenon that generates the colorful aurora, or Northern Lights. The radio waves are blocked by the ionosphere, a charged layer atop our atmosphere, so they do...