- William Henry Bragg with the first spectrometer. Image courtesy of the Royal Institution
In 1912, William Henry and son Lawrence were busy firing X-rays at crystals of salt. X-rays had been discovered 300 years earlier and still no-one was quite sure what they were. Earlier that year, a German physicist named Max Von Laue had found that X-ray light, when shone through a crystal, diffracted in a beautiful pattern. Months later, the Braggs were busy mimicking Von Laue’s experiment and trying to pin down the mysterious rays.
It was during these experiments that the Braggs realised that the light and dark spots produced through X-ray diffraction were related to the arrangement of atoms inside the crystal. They used the pattern to create a mathematical formula, Bragg’s Law, which showed how to work out the atomic structure of a sample based on the diffraction pattern it produced when exposed to X-rays.
The discovery was revolutionary, for the science of crystallography had been born. Bragg’s Law made it possible for scientists to see the world on an entirely different scale. For the first time, they could effectively pinpoint the particles inside their samples. The twentieth century saw scientists solve countless structures in this way, and these discoveries have led to the development of modern medicine, engineering and technology. By the end of the century, scientists knew more about the world around us than was ever thought possible.