In a South Korean laboratory, researchers have crossed a threshold that engineers have long approached but rarely reached: a device that draws power from the quiet decay of radioactive material, steadily and without interruption, for half a century. The Korea Electrotechnology Research Institute has demonstrated the nation's first silicon carbide betavoltaic cell, achieving a 60,000-fold improvement over previous domestic results and opening a path to autonomous power in the places most hostile to human presence. Where sunlight fails and maintenance is impossible — in orbit, beneath the ocean,