At a vast tract of uninhabited desert in southern Nevada, hundreds of moonlike craters dimple the wasteland, remnants of Cold War nuclear explosions that melted the bedrock and fused the sand to ensure that America could take part in the unthinkable: global thermonuclear war. The crowds of scientists and generals are long gone–the U.S. hasn’t tested a nuke since 1992, when then President George H.W. Bush declared a self-imposed testing moratorium. But the Nevada National Security test site is not completely abandoned. A skeleton crew of custodians oversees the long dormant facility, less than 90 miles northwest of Las Vegas, standing by to turn the lights back on if the day ever comes.