X-Rays
Year of Discovery: 1895
What Is It? High-frequency radiation that can penetrate through human flesh.
Who Discovered It? Wilhelm Roentgen
Why Is This One of the 100 Greatest?
If you have ever had an X-ray as part of a medical checkup, you owe thanks to Wilhelm Roentgen. Medical X-rays have been one of the most powerful, useful, and life-saving
diagnostic tools ever developed. X-rays were the first noninvasive technique developed to
allow doctors to see inside the body. X-rays led to the more modern MRI and CT
technologies.
Chemists have used X-rays to understand and decipher the structure of complex molecules (such as penicillin) and to better understand the electromagnetic spectrum. The discovery of X-rays earned Roentgen the 1901 Nobel Prize in physics.
How Was It Discovered?
In 1895 Wilhelm Roentgen was just a 40-something academic professor at the University of Wurzburg, Germany, doing ho-hum research into the effects of passing electricity
through gas-filled bottles. In November of that year he began experiments in his home basement lab with a Crookes’ tube (a device that amplified an electrical signal by passing it
through a vacuum).
On November 8, he happened to notice that a photographic plate that had been
wrapped in black paper and tucked inside a leather case in the bottom drawer of his desk had
mysteriously been exposed and imprinted with the image of a key. The only key in the room
was an oversized key for a garden gate he had tossed into the desk’s center drawer over a
year ago. The image on his photographic plate was of that key.
Even more strange, he found that the key in the center drawer lay along a straight line
from his glass Crookes’ tube mounted on the wall to the photographic plate deep in the bottom drawer. But no visible rays emitted from the Crookes’ tube and surely no light could
have penetrated through the desk and leather case to the photographic plate. What could
have mysteriously flown across the room and passed through wood, leather, and paper to
expose the photographic plate? Whatever it was, it could not pass through the metal
key—which was why a dark gray image of the key was outlined on his photograph.
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