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# Lawrence Bragg

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 Title: Lawrence Bragg Author: World Heritage Encyclopedia Language: English Subject: Collection: Publisher: World Heritage Encyclopedia Publication Date:

### Lawrence Bragg

This article is about the Australian born physicist. For his father and fellow Nobel Prize winner, see William Henry Bragg.

Sir William Lawrence Bragg
William L. Bragg in 1915
Born 31 March 1890
North Adelaide, South Australia
Died 1 July 1971 (aged 81)
Waldringfield, Ipswich, Suffolk, England
Nationality British
Fields Physics
Institutions University of Manchester
University of Cambridge
Alma mater University of Adelaide
University of Cambridge
Doctoral advisor J. J. Thomson
W.H. Bragg
Doctoral students John Crank
Ronald Wilfried Gurney
Alex Stokes
Known for X-ray diffraction
Bragg's Law
Notable awards Nobel Prize in Physics (1915)
Copley Medal (1966)
Notes
At 25, the youngest person ever to receive a Nobel Prize. He was the son of W.H. Bragg. Note that the PhD did not exist at Cambridge until 1919, and so J. J. Thomson and W.H. Bragg were his equivalent mentors.

Sir William Lawrence Bragg CH OBE MC FRS[1] (31 March 1890 – 1 July 1971) was an Australian-born British physicist and X-ray crystallographer, discoverer (1912) of the Bragg law of X-ray diffraction, which is basic for the determination of crystal structure. He was joint winner (with his father, Sir William Bragg) of the Nobel Prize for Physics in 1915: "For their services in the analysis of crystal structure by means of X-ray"[2] an important step in the development of X-ray crystallography. He was knighted in 1941. To date, Lawrence Bragg is the youngest Nobel Laureate, having received the award at the age of 25.[3] He was the director of the Cavendish Laboratory, Cambridge, when the epochal discovery of the structure of DNA was reported by James D. Watson and Francis Crick in February 1953.

## Biography

### Early years

Bragg was born in North Adelaide, South Australia. He showed an early interest in science and mathematics. His father, William Henry Bragg, was Elder Professor of Mathematics and Physics at the University of Adelaide. Shortly after starting school aged 5, William Lawrence Bragg fell from his tricycle and broke his arm. His father, who had read about Röntgen's experiments in Europe and was performing his own experiments, used the newly discovered X-rays and his experimental equipment to examine the broken arm. This is the first recorded surgical use of X-rays in Australia.

Bragg was a very able student. After beginning his studies at St Peter's College, Adelaide in 1904 he went to the University of Adelaide at age 14 to study mathematics, chemistry and physics, graduating in 1908. In the same year his father accepted the Cavendish chair of physics at the University of Leeds, and brought the family back to England. Bragg entered Trinity College, Cambridge in the autumn of 1909 and received a major scholarship in mathematics, despite taking the exam while in bed with pneumonia. After initially excelling in mathematics, he transferred to the physics course in the later years of his studies, and graduated with first class honours in 1911. In 1914 Bragg was elected to a Fellowship at Trinity College – a Fellowship at a Cambridge college involves the submission and defence of a thesis.[4][5]

### Career

#### Work on X-ray crystallography

Bragg is most famous for his law on the diffraction of X-rays by crystals. Bragg's law makes it possible to calculate the positions of the atoms within a crystal from the way in which an X-ray beam is diffracted by the crystal lattice. He made this discovery in 1912, during his first year as a research student in Cambridge. He discussed his ideas with his father, who developed the X-ray spectrometer in Leeds. This tool allowed many different types of crystals to be analysed.

#### Work on sound ranging

Bragg's research work was interrupted by both World War I and World War II. During both wars he worked on sound ranging methods for locating enemy guns. In this work he was aided by William Sansome Tucker, Harold Roper Robinson and Henry Harold Hemming. For his work during WWI he was awarded the Military Cross[6] and appointed Officer of the Order of the British Empire.[7] He was also Mentioned in Despatches on 16 June 1916, 4 January 1917 and 7 July 1919.[8][9][10][11]

On 2 September 1915 his brother was killed during the Gallipoli Campaign.[12] Shortly afterwards, William Lawrence Bragg received the news that he had been awarded the Nobel Prize in Physics, aged 25, making him the youngest ever winner of a Nobel Prize.[11]

Between the wars, from 1919 to 1937, he worked at the Victoria University of Manchester as Langworthy Professor of Physics. After World War II, he returned to Cambridge, splitting the Cavendish Laboratory into research groups. He believed that "the ideal research unit is one of six to twelve scientists and a few assistants".

#### Work on proteins

In 1948 he became interested in the structure of proteins and was partly responsible for creating a group that used physics to solve biological problems. He played a part in the 1953 discovery of the structure of DNA, in that he provided support to Francis Crick and James D. Watson who worked under his aegis at the Cavendish.

Bragg's original announcement of the discovery of the structure of DNA was made at a Solvay conference on proteins in Belgium on 8 April 1953, but went unreported by the press. He then gave a talk at Guys Hospital Medical School in London on Thursday 14 May 1953, which resulted in an article by Ritchie Calder in The News Chronicle of London on Friday 15 May 1953, entitled "Why You Are You. Nearer Secret of Life."

Bragg was gratified to see that the X-ray method that he developed forty years before was at the heart of this profound insight to the nature of life itself. At the same time at the Cavendish, Max Perutz was also doing his Nobel Prize winning work on the structure of haemoglobin. Bragg subsequently successfully lobbied for, and nominated, Crick, Watson and Maurice Wilkins for the 1962 Nobel Prize in Physiology or Medicine; Wilkins' share recognised the contribution made by researchers (using X-ray crystallography) at King's College London to the determination of the structure of DNA. Among those researchers was Rosalind Franklin, whose "photograph 51" showed that DNA was a double helix, not a triple helix as Linus Pauling had proposed. Franklin died before the prize (which only goes to living people) was awarded.

The crystal structure of hen egg white lysozyme, which was solved by D C Phillips et al. in 1965[13] under the directorship of Lawrence Bragg at the Royal Institution, London, led to the discovery of the $3_\left\{10\right\}$ helix. The lysozyme structure was determined from crystals of hen egg white lysozyme chloride, which belong to the tetragonal space group P$4_3$$2_1$2 with the unit cell dimensions a = b = 79.1 Å, c = 37.9 Å and have one lysozyme molecule in the asymmetric unit.[13] The existence of the $3_\left\{10\right\}$ helix, as opposed to Pauling's alpha helix, was predicted by W L Bragg, J C Kendrew & M F Perutz in 1950.[14] Apparently, many workers failed to mention the discovery of the $3_\left\{10\right\}$ helix, and failed to acknowledge the part it plays in the lysozyme structure. Pauling never acknowledged that at least part of the above mentioned 1950 paper made sense.

Unlike myoglobin, in which nearly 80 per cent of the amino-acid residues are in the alpha-helix conformation, in the lysozyme protein the alpha-helix content is only about 40 per cent of the amino-acid residues in four main stretches. The $3_\left\{10\right\}$ helix is an earlier proposal for the structure of polypeptides made by Bragg W L, Kendrew J C & Perutz M F in 1950. It is based on the crystallographic idea of an integral number of residues per turn of the helix. In this conformation, every third peptide is hydrogen-bonded back to the first peptide, thus forming a ring containing ten atoms.[15]

#### Lectures

In 1931, 1934 and 1961 Bragg was invited to deliver the Royal Institution Christmas Lecture on The Universe of Light, Electricity and Electricity.

### Personal life

He married Alice Hopkinson in 1921; she was a cousin of Bragg's friend Rudolph Cecil Hopkinson, killed in WWI. They had four children, Stephen Lawrence (born 1923), David William (born 1926), Margaret Alice, born 1931, (who married Mark Heath) and Patience Mary, born 1935. Bragg's hobbies included painting, literature and a lifelong interest in gardening.[16] When he moved to London, he missed having a garden and so worked as a part-time gardener, unrecognised by his employer, until a guest at the house expressed surprise at seeing him there.[17] He died at a hospital near his home at Waldringfield, Ipswich, Suffolk. He was buried in Trinity College, Cambridge; his son David is buried in the Parish of the Ascension Burial Ground in Cambridge, where Bragg's friend Rudolph Cecil Hopkinson is also buried.

## Honours and awards

He was elected an FRS in 1921—"a qualification that makes other ones irrelevant".[18] He was knighted by King George VI in the 1941 New Year Honours,[19] and received both the Copley Medal and the Royal Medal of the Royal Society. Although Hunter, in his book on Bragg Light is a Messenger, argued that he was more a crystallographer than a physicist, Bragg's lifelong activity showed otherwise—he was more of a physicist than anything else. Thus, from 1939 to 1943, he served as President of the Institute of Physics, London.[20] In the 1967 New Year Honours he was appointed Companion of Honour by Queen Elizabeth II.[21]

Since 1992, the Australian Institute of Physics has awarded the Bragg Gold Medal for Excellence in Physics[22] to commemorate Sir Lawrence Bragg (in front on the medal) and his father, Sir William Bragg, for the best PhD thesis by a student at an Australian university.

## Quotations

“The gift of expression is important to them as scientists; the best research is wasted when it is extremely difficult to discover what it is all about ... It is even more important when scientists are called upon to play their part in the world of affairs, as is happening to an increasing extent.”[23]

"The important thing in science is not so much to obtain new facts as to discover new ways of thinking about them."[24]

## Further reading

• Biography: Hunter, Graeme. Light Is A Messenger, the Life and Science of William Lawrence Bragg, ISBN 0-19-852921-X; Oxford University Press, 2004.
• John Finch; A Nobel Fellow On Every Floor, Medical Research Council 2008, 381 pp, ISBN 978-1-84046-940-0; (This book is about the MRC Laboratory of Molecular Biology, Cambridge.)
• Ridley, Matt; Francis Crick: Discoverer of the Genetic Code (Eminent Lives), first published in July 2006 in the United States, and then in the UK in September 2006, by HarperCollins Publishers; 192 pp, ISBN 0-06-082333-X (This short book is in the publisher's "Eminent Lives" series).
• John Jenkin: "William and Lawrence Bragg, Father and Son: The Most Extraordinary Collaboration in Science", Oxford University Press, 2008.

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