onehitwonder writes "Astronomers have discovered that the Earth emits awful, ear-piercing chirps and whistles that could be heard by any aliens who might be listening, according to an article up at Space.com. The sounds are created by charged particles from the solar wind colliding with Earth's magnetic field. This article explains more about the sounds and links to an audio recording of it."
You see but you do not observe.
Sir Arthur Conan Doyle, in "The Memoirs of Sherlock Holmes"