On this day in 1845, German physicist Wilhem Roentgen, the discoverer of x-rays, was born. Roentgen studied the flashes that occur in cathode ray tubes when electricity passes through a gas at extremely low pressure. The brightest flashes were from the electrons themselves. But in November 1895, Roentgen tried something a little different: He turned off the room's lights and put the cathode ray tube in a cardboard box. A mysterious glow appeared on the other side of the room.
Investigating further, Roentgen found that a paper plate covered with barium platinocyanide, placed in the path of the rays, glowed, and that objects in the path were of variable transparency. Placing his wife's hand between the cathode tube and a photographic plate, Roentgen made the first x-ray image, showing the bones of her hand and a ring she was wearing. He later demonstrated that x-rays were electromagnetic waves with a higher frequency than visible light. In 1901, Roentgen received the first Nobel Prize in physics for this work. He died in 1923.