The humble AM broadcast radio band can be an endless source of sonic fascination. In this excerpt, recorded at about 1:00am local time, I tuned my receiver to 1240 kHz — one of the so-called “graveyard” channels that contains scores of stations across the country broadcasting simultaneously at greatly reduced nighttime power. The result is a rich stew of not-quite-intelligible speech and music. Slow undulations in the Earth’s upper atmosphere cause the radio signals to bend, warp, and interfere with each other in complex ways en route to the receiver, giving rise to dramatic swirling, fluttering, and fading effects. In other words, you’re not just listening to the radio; you’re listening to the Earth’s atmosphere itself.