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History of Science

Examples of major events in science and how they have shaped the field.

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X the Unknown


X the Unknown


You probably recognize this picture as an X-ray image of a human hand. The hand has a big ring on the ring finger. This particular X-ray is the first X-ray image of a human body part ever made. It was taken by the man who discovered X-rays. The hand was his wife’s.

Why It Matters

  • Some of the most important discoveries in the history of science have been made by chance or by accident.
  • The discovery of X-rays by German physicist Wilhelm Roentgen in 1895 is a good example. Roentgen wasn’t looking for X-rays when he made the discovery. But Roentgen soon realized he had discovered a new type of rays. He named them X-rays, for X the unknown, because he didn’t know what they were.
  • Almost immediately, the medical use of X-rays was appreciated. X-rays would eventually revolutionize medicine. They would also lead to some amazing discoveries in science, from black holes in outer space to the shape of DNA.
  • Credit: John Lloyd
    Source: http://www.flickr.com/photos/hugo90/4176998349/
    License: CC BY-NC 3.0

    A car advertisement from 1961 that shows the lack of understanding of how X-rays work [Figure1]


  • You can watch a re-enactment of Roentgen’s discovery of X-rays in this video: http://www.youtube.com/watch?v=-OlOCxv1chM

Show What You Know

With the links below, learn more about X-rays and Roentgen’s discovery of them. Then answer the following questions.

  1. How did Roentgen accidentally discover X-rays?
  2. Shortly after Roentgen discovered X-rays, they were being used in medicine. How are X-rays used in medicine today?
  3. Explain how an X-ray image of bones, like the image above of Mrs. Roentgen’s hand, is made.
  4. X-ray machines generate X-rays in medicine. What are some natural sources of X-rays?
  5. How do scientists use X-rays? Identify an important discovery that was made using X-rays.
  6. Describe a practical use of X-rays outside of medicine or science.

Image Attributions

  1. [1]^ Credit: John Lloyd; Source: http://www.flickr.com/photos/hugo90/4176998349/; License: CC BY-NC 3.0


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