In 1895 the German physicist Wilhelm Röntgen, experimenting with a cathode ray tube, produced weak rays that caused a screen to fluoresce, or glow. In order to create a controlled environment, Röntgen placed the cathode tube in a black cardboard box, too thick for cathode rays to penetrate. Once the cathode-ray tube was turned on, however, Röntgen noticed that another screen across the room began to glow; since this second screen was too far from the tube for cathode rays to reach, especially through a layer of cardboard, Röntgen realized that he had discovered a new type of ray. Through experimentation he found that this new ray, unlike any others known at that time, was able to penetrate even the thick walls of his laboratory. Röntgen delivered a paper detailing his findings on December 28, 1895 in which he admitted that...