Lawrence Bragg

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

Sir
Lawrence Bragg
OBE MC FRS
Lawrence Bragg in 1915
Born
William Lawrence Bragg

(1890-03-31)31 March 1890
Adelaide, South Australia
Died1 July 1971(1971-07-01) (aged 81)
Waldringfield, Ipswich, Suffolk, England
EducationSt Peter's College, Adelaide
Alma mater
Known for
Bragg-Gray cavity theory
Bragg-Williams approximation
SpouseAlice Hopkinson (1899–1989)
Awards
Scientific career
FieldsPhysics
Institutions
Academic advisors
Doctoral students
Other notable studentsWilliam Cochran
Notes
He was the son of W. H. Bragg. The PhD did not exist at Cambridge until 1919, and so J. J. Thomson and W. H. Bragg were his equivalent mentors.
Portrait of William Lawrence Bragg taken when he was around 40 years old.

Sir William Lawrence Bragg,

OBE, MC, FRS[1] (31 March 1890 – 1 July 1971) was an Australian-born British physicist and X-ray crystallographer, discoverer (1912) of Bragg's law of X-ray diffraction, which is basic for the determination of crystal structure. He was joint recipient (with his father, William Henry Bragg) of the Nobel Prize in Physics in 1915, "For their services in the analysis of crystal structure by means of X-rays";[4] an important step in the development of X-ray crystallography.[5]

Bragg was

James D. Watson and Francis Crick
in February 1953.

Biography

Early years

Bragg was born in Adelaide, South Australia to Sir William Henry Bragg (1862–1942),[7] Elder Professor of Mathematics and Physics at the University of Adelaide, and Gwendoline (1869–1929), daughter of Sir Charles Todd, government astronomer of South Australia

In 1900, Bragg was a student at

Queen's School, North Adelaide, followed by five years at St Peter's College, Adelaide. He went to the University of Adelaide at the age of 16 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 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.[8][9]

Among Bragg's other interests was

shell collecting; his personal collection amounted to specimens from some 500 species; all personally collected from South Australia. He discovered a new species of cuttlefish – Sepia braggi, named for him by Joseph Verco.[10]

Career

X-rays and the Bragg equation

The composition of X-rays was unknown, his father argued that X-rays are streams of particles, others argued that they are waves. Max von Laue directed an X-ray beam at a crystal in front of a photographic plate; alongside of the spot where the beam struck there were additional spots from deflected rays – hence X-rays are waves.[11] In 1912, as a first-year research student at Cambridge, W. L. Bragg, while strolling by the river, had the insight that crystals made from parallel sheets of atoms would not diffract X-ray beams that struck their surface at most angles because X-rays deflected by collisions with atoms would be out of phase, cancelling one another out. However, when the X-ray beam struck at an angle at which the distances it passed between atomic sheets in the crystal equalled the X-ray's wavelength then those deflected would be in phase and produce a spot on a nearby film. From this insight he wrote the simple Bragg equation that relates the wavelength of the X-ray and the distance between atomic sheets in a simple crystal to the angles at which an impinging X-ray beam would be reflected.

His father built an apparatus in which a crystal could be rotated to precise angles while measuring the energy of reflections. This enabled father and son to measure the distances between the atomic sheets in a number of simple crystals. They calculated the spacing of the atoms from the weight of the crystal and the Avogadro constant, which enabled them to measure the wavelengths of the X-rays produced by different metallic targets in the X-ray tubes. W. H. Bragg reported their results at meetings and in a paper, giving credit to "his son" (unnamed) for the equation, but not as a co-author, which gave his son "some heartaches", which he never overcame.[12]

Work on sound ranging

Bragg was commissioned early in

Mentioned in Despatches on 16 June 1916, 4 January 1917 and 7 July 1919.[20][21][22]

Hot wire sound ranging was used in World War II during which he served as a civilian adviser.[23]

Between the wars, from 1919 to 1937, he worked at the Victoria University of Manchester as Langworthy Professor of Physics. He became the director of the National Physical Laboratory in Teddington in 1937.[24]

After World War II, Bragg 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".

University of Manchester (1919–1937)

When demobilised he returned to crystallography at Cambridge. They had agreed that father would study organic crystals, son would investigate inorganic compounds.[1][4] In 1919 when Ernest Rutherford, a long-time family friend, moved to Cambridge, Lawrence Bragg replaced him as Langworthy Professor of Physics at the Victoria University of Manchester. He recruited an excellent faculty, including former sound rangers, but he believed that his knowledge of physics was weak and he had no classroom experience. The students, many veterans, were critical and rowdy. He was deeply shaken but with family support he pulled himself together and prevailed. He and R. W. James measured the absolute energy of reflected X-rays, which validated a formula derived by C. G. Darwin before the war.[25] Now they could determine the number of electrons in the reflecting targets, and they were able to decipher the structures of more complicated crystals like silicates. It was still difficult: requiring repeated guessing and retrying. In the late 1920s they eased the analysis by using Fourier transforms on the data.

In 1930, he became deeply disturbed while weighing a job offer from Imperial College, London. His family rallied around and he recovered his balance while they spent 1931 in Munich, where he did research.

National Physical Laboratory (1937–1938)

He became director of the National Physical Laboratory in Teddington in 1937,[24] bringing some co-workers along. However, administration and committees took much of his time away from the workbench.

University of Cambridge (1938–1954)

Rutherford died and the search committee named Lawrence Bragg as next in the line of the Cavendish Professors who direct the Cavendish Laboratory. The Laboratory had an eminent history in atomic physics and some members were wary of a crystallographer, which Bragg surmounted by even-handed administration. He worked on improving the interpretation of diffraction patterns. In the small crystallography group was a refugee research student without a mentor: Max Perutz. He showed Bragg X-ray diffraction data from haemoglobin, which suggested that the structure of giant biological molecules might be deciphered. Bragg appointed Perutz as his research assistant and within a few months obtained additional support with a grant from the Rockefeller Foundation. The work was suspended during the Second World War when Perutz was interned as an enemy alien and then worked in military research.

During the war the Cavendish offered a shortened graduate course which emphasised the electronics needed for radar. Bragg worked on the structure of metals and consulted on sonar and sound ranging, for which the Tucker microphone was still used. Bragg was knighted and became Sir Lawrence in 1941. After his father died in 1942, Bragg served for six months as Scientific Liaison Officer to Canada. He also organised periodic conferences on X-ray analysis, which was widely used in military research.

After the war Bragg led in the formation of the

Guy's 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 nominated Crick, Watson and Maurice Wilkins for the 1962 Nobel Prize in Physiology or Medicine; Wilkins' share recognised the contribution of X-ray crystallographers at King's College London.[29] Among them was Rosalind Franklin, whose "photograph 51" showed that DNA was a double helix, not the triple helix that Linus Pauling
had proposed. Franklin died before the prize (which only goes to living people) was awarded.

The Royal Institution (1954–1971)

In 1953 the Braggs moved into the elegant flat for the Resident Professor in the

Brunel University."[30] He also introduced a programme of highly regarded Schools' Lectures, enlivened by the elaborate demonstrations that were a hallmark of the Institution. He gave three of these lectures on "electricity".[31]

He continued research in the Institution by recruiting a small group to work in the Davy-Faraday Laboratory in the basement and in the adjoining house, supported by grants he obtained. A visitor to the laboratory succeeded in inserting heavy metals into the enzyme lysozyme; the structure of its crystal was solved in 1965 at the Royal Institution by D. C. Phillips and his coworkers, with the computations on the 9,040 reflections performed on the digital computer at the University of London, which greatly facilitated the work.[32] Two of the illustrations of the positioning of amino acids in the chain were drawn by Bragg. Unlike myoglobin, in which nearly 80 per cent of the amino-acid residues are in the alpha-helix conformation, in lysozyme the alpha-helix content is only about 40 per cent of the amino-acid residues found in four main stretches. Other stretches are of the 310 helix, a conformation that they had proposed earlier.[33] In this conformation, every third peptide is hydrogen-bonded back to the first peptide, thus forming a ring containing ten atoms. They had the complete structure of an enzyme in time for Bragg's 75th birthday. He became Professor Emeritus in 1966.

X-ray analysis of protein structure flourished in subsequent years, determining the structures of scores of proteins in laboratories around the world. Twenty eight Nobel Prizes have been awarded for work using X-ray analysis. The disadvantage of the method is that it must be done on crystals, which precludes seeing changes in shape when enzymes bind substrates and the like. This problem was solved by the development of another line Bragg had initiated, using modified electron microscopes to image single frozen molecules:

cryo-electron microscopy.[34]

In his long association with the Royal Institution he was:

Personal life

In 1921 he married Alice Hopkinson (1899–1989), a cousin of a friend who had been killed in the war. They had four children, the engineer Stephen Lawrence (1923–2014), David William (1926–2005), Margaret Alice (1931–2022) (who married the diplomat Mark Heath), and Patience Mary (1935–2020). Alice was on the staff at Withington Girls' School until Bragg was appointed director of the National Physical Laboratory in 1937.[24] She was active in a number of public bodies and served as Mayor of Cambridge from 1945 to 1946.

Bragg's hobbies included drawing – family letters were illustrated with lively sketches – painting, literature and a lifelong interest in gardening.

Parish of the Ascension Burial Ground
in Cambridge, where Bragg's friend, who had he survived would have been his brother-in-law, Rudolph Cecil Hopkinson is also buried.

In August 2013, Bragg's relative, the broadcaster Melvyn Bragg, presented a BBC Radio 4 programme ("Bragg on the Braggs") on the 1915 Nobel Prize in Physics winners.[37][38]

Honours and awards

Bragg Family Blue Plaque Leeds

Bragg was elected a

Member of the Order of the Companions of Honour by Queen Elizabeth II.[41]

Since 1967 the

Lawrence Bragg Medal and Prize. Additionally since 1992, the Australian Institute of Physics has awarded the Bragg Gold Medal for Excellence in Physics[42] to commemorate Lawrence Bragg (in front on the medal) and his father, William Bragg, for the best PhD thesis by a student at an Australian university
.

The Electoral district of Bragg, in the South Australian House of Assembly, was created in 1970, and was named after both William and Lawrence Bragg.

See also

References

  1. ^
    JSTOR 769842
    .
  2. ^ "Alexander Stokes". The Telegraph. 28 February 2003. Retrieved 16 January 2016.
  3. ^ "National Library of Wales: From Warfare to Welfare 1939–59". Archived from the original on 18 November 2015. Retrieved 17 November 2015.
  4. ^ a b c "The Nobel Prize in Physics 1915". Nobel Foundation. Retrieved 26 April 2018.
  5. doi:10.1146/knowable-022822-1
    . Retrieved 25 March 2022.
  6. ^ "Facts on the Nobel Prize in Physics". Nobel Foundation. Retrieved 16 January 2016.
  7. doi:10.1093/ref:odnb/30845. Retrieved 29 December 2019. (Subscription or UK public library membership
    required.)
  8. ^ a b "Cambridge Physicists - William Lawrence Bragg". Cambridge Physics. Cavendish Laboratory. Retrieved 26 April 2018.
  9. ^ See Fred Hoyle's remarks regarding Hutchinson in 1965 Galaxies, Nuclei and Quasars p. 38 London: Heinemann; and R. J. N. Phillips 1987, "Some Words from a Former Student", in Tribute to Paul Dirac, Bristol: Adam Hilger, p. 31.
  10. ISBN 978 0 19 923520 9
  11. ^ Laue, Max von. "Concerning the Detection of X-ray Interferences". Nobel Prizes. Retrieved 3 January 2018.
  12. ^ Van der Kloot, William (2014). Great Scientists wage the Great War. Stroud: Fonthill. p. 129.
  13. ^ "No. 28879". The London Gazette. 25 August 1914. p. 6702.
  14. Notes and Records of the Royal Society
    , 22 September 2005, vol. 59, no. 3, pp. 273–284.
  15. ^ Van der Kloot 2014, pp. 129–161.
  16. ^ "Casualty Details: Bragg, Robert Charles". Commonwealth War Graves Commission. Retrieved 3 September 2010.
  17. doi:10.1098/rsbm.1972.0001
    .
  18. ^ "No. 30450". The London Gazette (Supplement). 1 January 1918. p. 32. MC
  19. ^ "No. 30576". The London Gazette (Supplement). 15 March 1918. p. 3289. OBE
  20. ^ "No. 29623". The London Gazette (Supplement). 13 June 1916. p. 5930. mid
  21. ^ "No. 29890". The London Gazette (Supplement). 2 January 1917. p. 207. mid
  22. ^ "No. 31437". The London Gazette (Supplement). 4 July 1919. p. 8523. mid
  23. ^ Van der Kloot 2014, pp. 207–208.
  24. ^ a b c Newsletter 1936-1937. Withington Girls' School. 1937.
  25. JSTOR 769264
    .
  26. ^ Phillips 1979, p. 117.
  27. ^ Phillips 1979, p.118
  28. S2CID 93804323
    .
  29. ^ "Maurice Wilkins – Facts". Nobel Prize. Nobel Foundation. Retrieved 26 April 2018.
  30. ^ Phillips 1979 ,p.126.
  31. ^ "William Lawrence Bragg (1890-1971)".
  32. S2CID 4161467
    .
  33. ^ Bragg et al. 1950.
  34. ^ "The Nobel Prize in Chemistry 2017".
  35. PMID 23250053
    . Retrieved 24 December 2012.
  36. ISBN 978-0140119732
    .
  37. ^ "Bragg on the Braggs".
  38. ^ "BBC Radio 4 - Bragg on the Braggs".
  39. ^ G. K. Hunter 2004 Light is a Messenger Oxford: OUP.
  40. ^ "No. 35029". The London Gazette (Supplement). 31 December 1940. p. 1. Knight bachelor
  41. ^ "No. 44210". The London Gazette (Supplement). 30 December 1966. p. 26. CH
  42. ^ Bragg Gold Medal for Excellence in Physics Archived 14 July 2014 at the Wayback Machine

Further reading

External links
Academic offices
Preceded by Langworthy Professor at the University of Manchester
1919–37 		Succeeded by
Professional and academic associations
Preceded by
Herbert Levinstein
 President of the Manchester Literary and Philosophical Society
1927–29 		Succeeded by
Charles Edmond Stromeyer
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