Crystallography and the Braggs: How X-ray Diffraction Revealed Atomic Structures

Overview

The video surveys X-ray crystallography as a defining 20th century innovation, tracing its origins to Max von Laue and the Bragg duo. It explains how a focused beam of X-rays diffracted by a crystal encodes the arrangement of atoms, with Bragg's law linking diffraction spots to lattice structure. The narrative follows the Braggs, their Nobel Prize, and the generation of crystallographers they mentored, including Kathleen Lonsdale, Dorothy Hodgkin, Rosalind Franklin, and Max Perutz. The talk also connects crystallography to DNA mapping and to modern applications ranging from turbine blades to immune responses, and even to Mars soil analysis by the Curiosity rover. It ends on the note that thousands of complex molecules remain to be explored, keeping the field vibrant.

Introduction and the Big Question

The video presents crystallography as a foundational method for understanding how matter behaves by revealing atomic arrangements. It frames the core idea that structure determines function, spanning phenomena from boiling points to DNA, and highlights the technique’s power in explaining materials and biology alike.

The Bragg Breakthrough

In 1913 William and Lawrence Bragg fired a narrow beam of X-rays at a salt crystal and photographed the resulting diffraction pattern. Lawrence recognized that the diffraction pattern held the clues to the crystal’s atomic structure. He developed Bragg's law, which connects the geometry of diffraction spots to the spacing of atoms in the lattice. By 1915 the Braggs were awarded the Nobel Prize, a milestone that anchored a new field.

The Braggs and Beyond

The Bragg team cultivated a generation of crystallographers including Kathleen Lonsdale, JD Burnell, Dorothy Hodgkin, David Phillips, John Kendrew, and Max Perutz. Rosalind Franklin and others contributed to the map of DNA, illustrating crystallography’s central role in one of biology’s most famous discoveries.

From Molecules to Planets

Today crystallography is used across scales, from the metallic structures in jet turbines to immune responses against viruses. Modern crystallographers employ larger data sets and advanced mathematics, and the field even extends beyond Earth, with the Curiosity rover performing X-ray diffraction analyses of Martian soil. Despite these advances, thousands of complex molecules remain to be explored, ensuring ongoing breakthroughs.

Current Frontiers and Future

The technique continues to evolve with improved machines and methods, driving discoveries in materials science, biology, and planetary science, while maintaining its status as a central tool for understanding the structure of matter and the behavior of materials.