Authors: Bill Bryson
Everyone in this story can trace a scientific lineage back to William Henry Bragg (FRS 1907) or his son William Lawrence Bragg (FRS 1921).
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Most would also credit the Braggs with establishing the egalitarian outlook that the early structural biologists shared. William H. Bragg was born in the UK and studied at Cambridge, but in 1885, at the age of twenty-three, he was appointed to the professorship in physics at the University of Adelaide. In 1909 he returned from Australia to take up the chair in physics at Leeds. His nineteen-year-old son Willie immediately went to
Cambridge to study natural sciences.
In 1912 the Munich-based physicist Max von Laue and his junior colleagues reported that a zinc sulphide crystal could diffract a beam of X-rays, producing a characteristic pattern of spots on a photographic plate and demonstrating the wave-like nature of X-radiation. Bragg
père
, who at that time inclined to the view that X-rays consisted of particles, was tipped off about the paper by a colleague who was working in Germany. When Willie came home for the long vacation they pored over the problem, and in subsequent months began their own experiments. Willie confirmed that X-rays formed diffraction patterns on passing through crystals (in the same way that light does on passing through narrow slits), and therefore behaved like waves. He went on to demonstrate that a simple mathematical formula (now known as Bragg’s Law) could relate the positions and intensities of the spots in the pattern to the positions of the parallel layers of atoms in the crystal from which the X-rays were reflected. The formula required a figure for the wavelength of the X-rays, and the Braggs were able to measure this using an X-ray spectrometer of Bragg senior’s invention. Applying the formula to X-ray photographs of simple compounds such as sodium chloride, Willie Bragg was able to draw a picture of the sodium and chlorine atoms neatly alternating throughout the cubic lattice, like the simplest of wallpaper patterns but in three dimensions.
The Braggs had turned X-ray diffraction from an intriguing observation into a tool for exploring what matter is made of in the range that was too small to be seen with a microscope, and too large for chemical analysis. They shared the 1915 Nobel Prize in physics for their discovery. The announcement came when the younger Bragg, aged only twenty-five, was in France developing sound-ranging techniques to help the allies in the war against Germany to fix the coordinates of enemy artillery batteries. He remains the youngest person ever to win a Nobel. Years later Max Perutz summed up the range of discoveries that subsequently flowed from the Braggs’ achievement:
Why water boils at 100°[C] and methane at -161°, why blood is red and grass is green, why diamond is hard and wax is soft, why graphite writes on paper and silk is strong, why glaciers flow and iron gets hard when you hammer it, how muscles contract, how sunlight makes plants grow and how living organisms have been able to evolve into ever more complex forms … The answers to all these problems have come from structural analysis.
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Knighted in 1920, Sir William Bragg moved to London as Professor of Physics at University College (UCL), and then Director of the Davy-Faraday Laboratory at the Royal Institution (RI), a post that he held from 1923 until his death in 1942. A central figure in British science, he was also President of the Royal Society from 1935 until 1940. Long before ‘public understanding of science’ became a topic of debate, Bragg retained the nineteenth-century assumption that new discoveries in science should be part of public discourse, and was an enthusiastic writer and speaker. In 1919 he gave the Christmas Lectures for children at the Royal Institution on the subject ‘Concerning the Nature of Things’; six years later he again fascinated his young audience with his series ‘Old Trades and New Knowledge’. Both series were published as books, and contained some of the first public descriptions of the capacity of X-ray crystallography to open up new perspectives:
The discovery of X-rays has increased the keenness of our vision … a thousand times, and we can now ‘see’ the individual atoms and molecules.
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From the early 1920s Bragg began to use X-ray crystallography to investigate organic molecules (those containing carbon, which include all the molecules that make up living things) rather than the simple, inorganic salts that his son continued to work on as a very young professor at Manchester. Now well into his sixties and with heavy administrative responsibilities at the RI, Sir William recruited young men and women to join his endeavour in the laboratories where Humphry Davy and Michael Faraday had conducted their chemical and electrical experiments a century before.
Bill Astbury (FRS 1940), the son of a potter from Stoke on Trent, had gone to Cambridge on a scholarship and graduated with a First in Natural Sciences. Joining Bragg as a postgraduate at UCL and the RI, he began to use X-ray diffraction to study the structure of natural fibres such as wool that are made of large, complex protein molecules. In 1928 he moved to the University of Leeds, an important centre of the textile industry, where he continued to develop the technique of fibre diffraction. During the 1930s he was the first to take X-ray photographs of DNA fibres (long before anyone had established its significance as the molecule of heredity). Although he was not able to obtain definitive structures, his insights into the ‘coiled’ nature of these molecules were fundamental to later discoveries by Linus Pauling (the alpha helix of proteins) and Maurice Wilkins, Rosalind Franklin, James Watson and Francis Crick (the DNA double helix).
Kathleen Yardley (later Lonsdale, FRS 1945) was the tenth child of an Irish postmaster who had a drink problem. Her mother brought the family to England for a better life, and in 1922 Yardley graduated from Bedford College (a women’s college of London University) with the highest mark in physics that anyone in the university had achieved for ten years. Bragg immediately wrote to recruit her as his research assistant. When she married fellow
researcher Thomas Lonsdale and had three children, Bragg kept her supplied with work she could do at home, then found her a grant to pay for domestic help so that she could come back to the lab. This concern to create conditions in which a married woman could pursue a scientific career was wholly exceptional at the time, as was Thomas Lonsdale’s willingness to share domestic chores and support his wife in her career. Kathleen Lonsdale clarified the structure of a number of small organic molecules, notably confirming that benzene was a flat ring of six carbon atoms, each with a hydrogen attached.
Tiny, courageous and independent, Lonsdale dealt with glass ceilings by refusing to see them, and achieved a series of notable firsts for British women in science. In 1945 she and Marjorie Stephenson, the Cambridge biochemist, signed the Register of Fellows of the Royal Society, the first women to do so since its foundation in 1660. Their election followed delicate political manoeuvring largely on the part of the then President, Sir Henry Dale (who became Lonsdale’s boss at the RI after William Bragg’s death in 1942) to overturn what prejudice remained among the Fellowship after legal obstacles were removed in 1919. She also benefited from the energetic advocacy of her erstwhile fellow graduate student, Bill Astbury. It was his presentation of a correctly drawn up certificate of her candidacy that prompted Dale to win the majority of the Fellowship over to this revolutionary move.
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In 1949 Lonsdale became the first woman to be appointed to a professorship at University College London, and in 1968 the first to become President of the British Association for the Advancement of Science. A Quaker and conscientious objector, in 1943 she refused to pay the fine of £2 for nonregistration for civil defence work, an action that earned her a month in Holloway prison. Appalled at the monotony of prison life, she became an active supporter of prison reform after her release. At the height of the Cold War she wrote a book,
Is Peace Possible?
,
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giving a personal response to her ‘sense of corporate guilt and responsibility that scientific knowledge should have been so misused’ as to develop atomic weapons. Her example was an inspiration to the generations of women crystallographers who followed.
Also born in Ireland, to a comfortably-off farming family, John Desmond Bernal
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had astonished his Cambridge tutors as an undergraduate by producing unbidden an eighty-page manuscript giving mathematical derivations of the 230 ‘space groups’ of classical crystallography. The diversion of his efforts probably cost him a First, but left them in no doubt of his quick grasp of theoretical concepts, and like Astbury he came to Bragg with their enthusiastic recommendation. Though he never completed a PhD thesis, during his time at the RI he solved the structures of single crystals, notably graphite, designed the X-ray goniometer that all crystallographers used to mount and photograph their crystals for years afterwards, and made further theoretical contributions to the subject. In 1927 he returned to Cambridge as the first Lecturer in Structural Crystallography in the department of mineralogy.
Bernal was a polymath, able to discourse convincingly and at length on any topic from Chinese art to quantum physics. While still an undergraduate he had earned the nickname ‘Sage’ from his fellow students: the name stuck throughout his life, used by all his friends and colleagues with barely a trace of irony. Nor were his energies confined to intellectual pursuits.
Exchanging devout Roman Catholicism for equally devout Marxism as an undergraduate, he became a leading member of the ‘visible college’ of scientists and socialists who came to prominence in the 1930s.
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Always linking thought to action, he was an indefatigable organiser, notably of the Association of Scientific Workers and later its international counterpart, the World Federation of Scientific Workers. His desire for experimentation extended far outside the laboratory: he pursued a private life of unabashed promiscuity, justified to himself and others by his political mission to escape the restrictions of social convention.
Bernal was unusual among scientists in the degree to which he reflected on his experiences and beliefs in both public and private. In his early life he kept diaries charting everything from his scientific and political insights to his sexual conquests, and at the age of only twenty-five began a passionate and idealistic memoir (never published) entitled
Microcosm.
Soon afterwards he produced his first published book,
The World, the Flesh and the Devil: An Enquiry into the Future of the Three Enemies of the Rational Soul
(1929), which accurately predicted a number of scientific developments including the Apollo space programme, and just as inaccurately forecast the triumph of world Communism. A later and much more influential book,
The Social Function of Science
(1939), argued for central planning of science on the Soviet model, with the goal of improving human welfare rather than pursuing knowledge for its own sake.
The Second World War gave Bernal the opportunity to put his own science to the service of society. He was involved in studies of the accuracy of bombing raids and their effects, which influenced both civil defence policy and Bomber Command, and conducted surveys of the Normandy coastline and seabed as part of the preparation for the D-day landings. After the war he aligned himself, like many of his fellow scientists, with opposition to nuclear warfare, coining the phrase ‘weapons of mass destruction’ at a speech to the British-Soviet Society in London in 1949. His influence might have been greater had it not been for his blindly
uncritical support for Soviet Communism, which was unwavering in the face of Stalin’s purges, the Lysenko affair and the invasion of Hungary. His accusation that the direction of Western science was dictated by warmongers led to his removal from the Council of the British Association for the Advancement of Science. Despite his valuable service during the war years, he never received any honours in Britain.
The double Nobel Prize-winner Linus Pauling (For.Mem.RS 1949) is one of many who described Bernal as the most brilliant scientist they had ever met. Yet he never personally made the kind of breakthrough that would have set him on the road to Stockholm. With so much to do, and so little time, he rarely pursued a scientific project to its conclusion. Instead, he gathered around him a group of able disciples of both sexes and showered them with ideas. They did not let him down.
Dorothy Crowfoot (later Hodgkin
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) was a slim, soft-spoken, first-class graduate in chemistry from Oxford who came to Bernal’s lab in 1932 to begin a PhD. The eldest of four girls, Crowfoot came from a middle-class family who did not see intellectual pursuits as off-limits for women. Her father was a colonial administrator and archaeologist, and her mother, without any formal higher education, became a world expert in ancient textiles. It was she who encouraged Crowfoot’s schoolgirl interest in chemistry by giving her W.H. Bragg’s collected lectures to read, and his account of crystallography captured her imagination.
Crowfoot excelled in all the practical aspects of crystallography – growing the crystals, mounting them and photographing them – but also had a remarkable ability to visualise the three-dimensional manipulations that the early, trial-and-error stage of the subject demanded. She quickly became Bernal’s right hand, conducting preliminary observations on the dozens of crystals that poured into his lab from all over the world. Asked
later how she succeeded so early, she modestly replied that there was so much gold lying about, one could not help picking it up.
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One day Glenn Millikan, a young scientist and friend of Bernal’s, returned to Cambridge from Sweden with a tube of crystals of the digestive enzyme pepsin in his pocket. Like all enzymes pepsin is a protein, one of a class of biological molecules that are the precision tools of the living body. Enzymes are highly specific catalysts that speed the construction and destruction of all the body’s constituents; other proteins include keratin and collagen that build strong structures such as hair and skin, antibodies that protect us against disease, and hormones such as insulin. All proteins depend for their function on their molecular structure. With care they can be purified and crystallised just like simple salts (though the crystals tend to be very small). The fact that they crystallise at all implies that their molecules have a regular structure – something that not all chemists believed at the time – and Bernal was convinced that solving these structures would reveal the ‘secret of life’.