10 of History's Happiest Accidents

X-ray Images
In this illustration from 1903, a doctor examines a patient's thorax using an X-ray tube and fluorescent screen. X-rays were discovered in 1895 and immediately used in medicine. Universal Images Group Editorial/Getty Images

Over the course of one short year at the turn of the 20th century, one man's accidental discover revolutionized the practice of medicine.

In 1895, Wilhelm Conrad Roentgen was a little-known German physicist researching the behavior of cathode rays. In those days, no one knew anything about electrons or radiation. Roentgen was running high-voltage current through vacuum tubes to study the escaping cathode rays. He was surprised to find, though, when he covered the tube with black cardboard, that some invisible rays were still able to illuminate a screen coated with platinobarium 9 feet (2.7 meters) away [source: American Physical Society]. He called the unknown phenomena "X-rays."

In short time, Roentgen discovered that X-rays could also be captured on photographic plates. Using his wife's hand as a test subject — what a gentleman! — he was floored by the resulting image. X-rays passed easily through skin and muscle, but were blocked by bone and metal. For the first time, we could see inside the human body without raising a scalpel.

The medical community leaped on the invention, which Roentgen generously refused to patent. Within a year, the first diagnoses of broken bones and swallowed coins were being made by X-ray [source: APS]. Soon the mysterious rays were being used to treat cancerous tumors and skin diseases. The dangerous effects of X-ray exposure weren't known initially, but now doctors and technicians take special precautions to avoid the side effects of radiation [source: British Library]. Roentgen received the very first Nobel Prize in physics in 1901.