As a child, I took it upon myself to exact the half-life of oblivion from everything I encountered. Each birthday, I asked for a bright-yellow, Civil Defense–style Geiger counter to help me in this task. Each birthday, I was denied. As a consolation prize, my grandmother bought me two banana-hued pencil dosimeters at a yard sale. They bore the iconic insignia of the Civil Defense: a bold blue circle holding a white triangle with a C and D in rounded, scarlet script. She explained that they were not actually pencils—you couldn’t write with them. The designation had to do with their shape, slender and tall, and made to fit in your pocket. I was delighted with my dosimeters and carried them with me everywhere, imagining all the radiation they were soaking up. Every so often I held them to my ear, like a seashell, and listened. I drew them close to my Sony Sports Walkman, yellow on yellow, like a goldfinch on a forsythia bush. I pretended my Walkman was not a cassette tape player but a Geiger counter, a machine that could detect histories of radiation played in reverse. Without a proper Geiger counter I could never really hear the telltale sign of radiation detection—like mechanical beetles bouncing off each other in a tall jar—but I realized that silence is a kind of ticking, too.