A hidden gap in the interstices of Columbia University’s military-disciplinary programs offers an invitation to listen deeply to past and present, mediated by the body. In 1939, the Manhattan Project was midwifed in the basement of Pupin Physics Hall on Columbia’s Morningside campus. The project’s particle accelerator was arranged behind barrier walls of water tanks to absorb the radiation emitted from its operation. In the decades intervening, a new gymnasium was constructed above the site of the former cyclotron, the newly obstructed windows of the physics lecture halls filled with plaster, and the exterior campus level raised, submerging three building stories. There remains a 6-foot wide gap between the walls of Pupin and Dodge Fitness Center, secreted between the activities of disciplining the mind and disciplining the body. It is into this spatial interval that one might slip, quietly, through the forgotten openings, and become still, and let sound enter in. Percussion, echo. In answer to violence, we must relearn how to be vulnerable.