The humble Braggs and X-ray crystallography

Solving the patterns of matter

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The story of X-ray crystallography

As the field of crystallography celebrates its centenary year we look back at how it all began – with a father and son team and a humble salt crystal.

With the help of archive footage and historic objects from the Ri, Patience Thomson, daughter of William Lawrence Bragg, presents an intimate portrait of her father. From his detailed artworks to his love of detective stories and puzzles, Patience reveals how Lawrence’s unique character and analytical mindset led to numerous scientific breakthroughs.

Plus, find out how he reacted to receiving news of his Nobel Prize while serving on the front during WW1 at the age of 25 and discover how the Braggs applied their scientific knowledge to aid the war effort. 

Professor Stephen Curry is also on hand to demonstrate just how important the Braggs’ discovery was and how the field of x-ray crystallography has revealed the structure of hundreds of different molecules, from enzymes and proteins to entire viruses. The Braggs’ discoveries of 1913 remain at the foundation of modern day techniques and, to date, 29 Nobel Prizes have been awarded to work related to x-ray crystallography.

Our thanks to Stephen Curry, Patience Thompson, and filmmaker Thom Hoffman.

This film was supported by the Science and Technologies Facilities Council (STFC).


Materials, Talking Science


Patience Thomson, Professor Stephen Curry
Royal Institution, London / Oxfordshire

Thom Hoffman

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cc_by-nc-nd License: Creative Commons



My name is Patience Thomson, born Bragg. I was the youngest child of William Lawrence Bragg and the granddaughter of WH Bragg, whom I just dimly remember.

We have this bust of my father, which I absolutely love. It's a very, very good likeness. It moves and stirs me every time I see it.

William Henry and William Lawrence Bragg were the first father and son team to win a Nobel Prize for a discovery that shone a new light on the structure of our world. And it all started with an x-ray.

Most people know what an x-ray is, or they think of the shadowy photograph that they've seen of a broken leg or a broken arm. So they know that x-rays is a powerful special type of light and that it can pass through most forms of matter and certainly can pass through biological tissue. But it's absorbed by bone, which is why it leaves a shadow.

In 1912, Max von Laue was firing x-rays at crystal samples and becoming intrigued by the patterns that were formed. But he couldn't make complete sense of what they meant. WH Bragg showed his son Lawrence these diffraction patterns.

Well, like everybody else, he saw a pattern of spots. But I think he also saw a puzzle, and a puzzle that needed to be solved.

He loved detective stories. That was his great thing. One of his great mortifications is that he once sat next to Agatha Christie at dinner and was introduced by her married name and didn't realise who she was. My mother said afterwards, you must have had a marvellous time sitting next to Agatha Christie. And he said, what?

OK. So maybe Lawrence wouldn't have made a great detective. But when it came to piecing together scientific clues, it was a different matter.

He just looked at the problem in a completely different way to Laue, and he saw what the solution was.

He noticed things that other people didn't notice. Everybody was looking at those Laue x-rays and trying to get an interpretation. Typical of my father to see that, in fact, a two-dimensional sheet could be transformed into a three-dimensional model. Ping pong balls and rods.

This is one of the very first diffraction patterns that the Braggs themselves would have taken. And it's taken from a crystal of salt. You can see the very particular pattern. Each of these spots represents the end of a diffracted ray. And it was their particular insight that showed us how to interpret this pattern in terms of the atomic structure within the crystal.

William Henry had been thinking of x-rays as particles. However, Lawrence suddenly had an insight about the nature of crystals themselves.

So what is it really that makes a thing a crystal? It's its inside arrangement. It's the fact that the molecules or atoms in it are in an absolutely regular pattern, like soldiers on parade or like the pattern of a wallpaper.

The atoms are arranged in layers or in two-dimensional planes that go all the way through the crystal. And so he realised that each one of these acts like a semi-transparent mirror. What's happening is that the x-ray is reflecting off the top layer but also off the next layer underneath and off the layer underneath that, and the x-rays bounce off those planes in all sorts of directions. By thinking of the problem simply as reflection, he was able to figure out how the atoms were arranged exactly and produce this model in fact, which is the very first atomic structure of a crystalline sample that was ever solved.

He liked to make connections. He liked always to be building up a picture increasing insight.

Scientists finally had the ability to look at the atomic structure of matter. And they could start to understand some of the physical properties of matter, in terms of the underlying atomic structure. And that was an enormous breakthrough. He didn't realise probably at that stage how massive the breakthrough he'd just made had been.

His solution was almost always the simplest. The same in his watercolours, with the almost professional ability to bring out the important things. And the same in his articles. He would give visual illustrations. It wasn't tell me. It was show me.

And it helped to explain why it is that these two forms of carbon have such different properties. Diamond is one of the hardest substances that we know of. And the atomic structure shows that that strength arises because the atoms are bonded to each other very closely and in all three directions.

Whereas in graphite, you've got these close hexagonal nets. But the whole structure is layered, and they can slide easy past one another. Graphite is also a pure form of carbon, but it's much softer. That very softness arises from the fact that these layers are not tightly bonded to one another. And that was first revealed by x-ray crystallography.

Well, the great, great breakthrough on crystallography came when he was walking along The Backs in Cambridge and suddenly had a blinding insight. But it could be when he was doing the washing up. He didn't have to be in a rarefied atmosphere to have these ideas. You felt that his brain was working all the time and that he liked to have some problem to crunch on.

The Braggs' work on crystallography was disrupted during World War I, with Henry moving into submarine detection and Lawrence being sent to the front line. But their insights led to a shared Nobel Prize in 1915, with Lawrence becoming the youngest Nobel winner in history at just 25.

My father heard that he had won the Nobel Prize when he was in the trenches. He was obviously extremely chuffed and pleased, but I think the world was in such total disarray around him that it all must have seemed rather remote.

He now turned to using science to fight against the German Army's superior weaponry.

The German Army had the upper hand very often, because they had much more powerful guns. And my father was asked to establish a system of working out, by listening to the sounds and comparing how long it took them to get to various different points, exactly where the location of the guns were. In the obituaries on my father, it did say that his team shortened the war, because they, could put the enemy guns out of action.

Back in peace time, the field of x-ray crystallography went from strength to strength. The discoveries by the Braggs and their successors kept coming, and the technique was used to solve increasingly complex structures, such as graphite, penicillin, DNA, and, more recently, whole viruses. To date, crystallography has been a feature of 29 Nobel Prizes.

The application of this technique transformed our understanding of matter in so many different fields, not just in geology, understanding minerals, but in chemistry understanding how different chemicals are built up, and then, finally, brought us into the realm of biology, where we could figure out how it is that the molecules that exist within us are coordinated and work together in order to sustain life. And these days, it's kind of a shame he's not with us now, because I think he would just be enormously impressed to see how the technique has developed even since 1971, just the size and the scale and ambition of the types of problems that people are tackling now. Whole virus particles have been crystallised and solved. We are simply getting better and better at doing crystallography.

The Curiosity Rover that NASA sent to Mars last year has got an x-ray diffraction instrument on the Rover that's trundling over the surface. And so it can pick up samples of soil, and it can analyse the minerals that are in the soil on Mars.

He liked Agatha Christie, I think, because in the last chapter everything falls into place. He liked neat endings.

They're still winning Nobel Prizes, and I don't see that slowing down.

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