Newspaper article The Christian Science Monitor

Google Honors Dorothy Hodgkin's X-Ray Vision

Newspaper article The Christian Science Monitor

Google Honors Dorothy Hodgkin's X-Ray Vision

Article excerpt

In her acceptance speech for the 1964 Nobel Prize in Chemistry, Dorothy Hodgkin quoted a children's book by the eminent British scientist Sir William Henry Bragg:

"Broadly speaking," wrote Bragg in 1925, "the discovery of X- rays has increased the keenness of our vision over ten thousand times and we can now 'see' the individual atoms and molecules."

X-rays are most famous for their ability to pass through solid matter. That's what makes them popular in dentists' offices and airport security zones, for instance. Less well-known is their ability to help us determine the very structure of matter itself.

The science of X-ray crystallography began in April 1912, when the German physicist Max Laue and his colleagues placed a copper sulfate crystal between an X-ray tube and a photographic plate. As the X-rays passed through the crystal, bright spots on the photographic plate appeared, forming a distinct pattern. Just as waves in a lake striking a buoy produce secondary waves that ripple outward from the buoy, the X-rays, upon encountering the electrons in the crystal, had diffracted, leaving behind clues about the crystal's structure.

In this single experiment, Laue had uncovered two momentous facts about the natural world. First, that crystals formed a regular lattice structure; and second, that X-rays traveled like waves, and were thus a form of electromagnetic radiation, just like visible light. With uncharacteristic swiftness, the Royal Swedish Academy of Sciences awarded him the Nobel Prize in Physics less than 19 months later.

In the meantime, William Bragg, and his son, Lawrence, were busy working out the precise connection between the diffraction patterns and the atomic structure of crystals. After firing an X-ray beam at salt crystals and observing the patterns that the beam made on a photographic plate, Lawrence Bragg formulated what would come to be known as Bragg's law, which describes the mathematical relationship between the X-rays' wavelength, the distance between the planes in the crystals' lattice, and the angle at which the X-rays are reflected.

Their work earned the father-and-son team the 1915 Nobel Prize in physics and led to the creation of a new scientific field: X-ray crystallography. …

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