A camera on a tripod, set for a five-second exposure, takes in far more light than the human eye does when it looks at something, and consequently it produces a more vivid image. A camera on a tripod, set for a five-second exposure, takes in far more light than the human eye does when it looks at something, and consequently it produces a more vivid image. On January 31, 1913, King Haakon VII of Norway went to the University of Oslo to hear a lecture by the physicist Kristian Birkeland, who believed that he had unlocked the secrets of the aurora borealis, also known as the northern lights. Birkeland planned to demonstrate his theory with the aid of a specially constructed device: a brass-plated magnetic sphere, called a terrella, suspended inside a vacuum chamber with glass sides and an electrode on one end. When the electrode was heated, it would shoot cathode rays across the chamber toward the sphere. If all went well, the rays would interact with the sphere’s magnetic field, producing eerie flashes of light that replicated, in miniature, the aurora borealis. As Birkeland’s biographer Lucy Jago tells it, the lecture was a triumph. The contraption didn’t electrocute anybody or i...