RETROSPECTIVE Donald Lynden-Bell (1935–2018) RETROSPECTIVE Martin J. Reesa,1 Donald Lynden-Bell was lucky in his heredity and his his course on statistical me- environment. His great-grandfather knew the famous chanics. It was one of his fa- astronomer John Herschel. His father, an army Colo- vorite subjects and he gave nel, inherited a telescope and introduced Donald to spirited performances. But the wonders of the sky. At his school, Marlborough Donald felt his teaching obli- College, Donald was exceedingly well taught. He came gations didn’t leave enough up to Clare College to read mathematics. In his second time for research, so he soon year, he was supervised by the great physicist Abdus moved to the Royal Observa- Salam, who advised him to divert for a year to study tory at Herstmonceux in Sussex. physics, which Donald did before returning to mathe- It was there that Donald’s matics for his fourth year. He thereby had a superb most-quoted paper gestated launching-pad for research. (2): his prescient idea that mas- Donald’s doctoral supervisor was Leon Mestel, a sive black holes lurk in the cen- world expert on cosmic magnetism. But Donald found ters of galaxies, and shine Leon’s problems “too intractable,” so instead he be- brightly because gas gets gan to forge his lifetime interest in stellar dynamics: heated by viscous friction as it how swarms of stars configured into the distinctively swirls down into them. This was shaped clusters and galaxies that populate the cosmos. a key to understanding the At that time the British had no access to world-class mysterious quasars, discovered optical telescopes; California was the mecca for astron- a few years earlier by Maarten omers. So after Donald got his doctorate in 1960, he Schmidt at the California Institute spent 2 formative years in Pasadena, California, where of Technology. Forty years later, he had the luck to “click” with Allan Sandage, the high Donald and Schmidt shared Donald Lynden-Bell. Image courtesy of priest of astronomy at that time. Their joint project led the first Kavli International Prize Amanda Smith and the Institute of to Donald’s first really famous paper (1): inferring how in astronomy. Astronomy, University of Cambridge. our Milky Way galaxy formed from a primordial spin- In 1972 Donald moved back ning gas cloud, and what we could learn about its his- to Cambridge to direct the new tory from the orbits of the oldest stars. Institute of Astronomy, which merged Cambridge’s While in California, Donald met other British astron- long-established Observatory with the adjacent theo- omers. Fifty years later, four of them had a reunion: they retical institute founded 5 years earlier by Fred Hoyle. retraced a mountain hike they’dmadeaspostdoctor- This was a challenging period because Hoyle’s funding ates. A talented film-maker, Alison Rose, accompanied had expired and it was hard to pay the staff. them and created a movie called Star Men, in which the I was then at Sussex University, but a year later was protagonists (all elderly) reminisced about life, the uni- elected to the other Chair in the Institute. This couldn’t verse, and everything. Donald, a keen mountaineer in have happened without Donald’s approval and it was his youth, enjoyed making this movie and spoke at a privilege and pleasure to be his colleague. For more several special showings. than 20 years we alternated harmoniously as director. But the most important event for Donald in his Our discussions on administration were generally postdoctorate years was his marriage to Ruth in 1961. enlivened by zany digressions into whatever scientific She moved to California to finish her chemistry doctor- puzzle was on his mind. ate, but they both returned to Cambridge in 1962. Donald cared about all of the staff and students Donald then became an assistant lecturer in and about ensuring a friendly atmosphere. He cared mathematics and a Fellow of Clare College. I attended about the physical environment as well; in the early aInstitute of Astronomy, CB3 0HA Cambridge, United Kingdom Author contributions: M.J.R. wrote the paper. The author declares no conflict of interest. Published under the PNAS license. 1Email: [email protected]. www.pnas.org/cgi/doi/10.1073/pnas.1803355115 PNAS Latest Articles | 1of2 Downloaded by guest on October 2, 2021 days, Donald had an allotment in the grounds. And it’s must have been a special pleasure when Ruth became thanks to him that there are now so many spring flow- a Fellow of the Royal Society too. ers around the Institute. Those who founded the Royal Society in 1660 were Donald admired the great Arthur Eddington and described as “ingenious and curious gentlemen.” Don- would have appreciated retracing his career path to ald joined more than 300 years later, but it strikes me the Royal Observatory and then to Cambridge. Like that this phrase fit him well. Eddington, he engaged with fundamental questions. Donald was ingenious: his inventive ideas spanned a As a student, Donald thought about the origin of mass huge range. He never minded being unconventional... and inertia: Mach’s principle. His last paper, written indeed, he preferred being unconventional. He was cu- with Kumar Chitre, was a highly original conjecture on rious. Right until last year—15 years after his official re- where the entropy came from after the big bang (3). tirement—Donald regularly attended Institute colloquia But Donald’s view was that we shouldn’t spend all and coffee-time discussions. He always had lively ques- of our time groping at fundamental problems. We tions. He really wanted to understand what we were should mainly do “bread and butter” science: straight- doing. Donald said, “I’m not ashamed to ask questions forward extensions of what is known. That’s the mod- that others claim are nonsensical.” est way he would have described much of his work. And Donald was a gentleman: absolutely not in the But what made Donald special was his versatility. He “entitlement” sense of that word—he was allergic to proposed new designs for telescopes; he explained extravagance, to formality, and to badges of status— how Jupiter’s radio bursts could be triggered by one but through his courtesy and concern for everyone. of its moons; above all, he published extensively on Staff, students, and especially foreign visitors appreci- stars, galaxies, quasars, and the entire cosmos, even— ated the hospitality that Donald and Ruth offered at to Leon Mestel’s pleasure—developing neat ideas on their home. And it was perhaps his traditional back- magnetic fields. ground that deepened his commitment to serve insti- Donald worked with a diverse range of collabora- tutions, not only Cambridge but also the Royal tors, hailing from all over the world, but intensively, one Astronomical Society. at a time. Each paper normally had only one coauthor. We will all have our memories of Donald, and our But in the 1980s he joined a bigger collaboration, as personal reasons to be grateful to him. What’sremark- the gadfly and mathematician in an international group able is how little he changed, physically and mentally, that became known as the “Seven Samurai.” They ob- over his 45 years at the Institute. However, just the day served hundreds of galaxies and found that these were after he’d celebrated Ruth’s 80th birthday, a devastating all being pulled by the gravity of a huge hidden mass stroke snuffed him out so suddenly that we never had they dubbed “the Great Attractor.” the chance to convey our admiration and gratitude. Donald received many honors, including a CBE Donald left an enduring scientific legacy as one of from the government of the United Kingdom. He the great astronomers of his generation. And, more received the Gold Medal of the Royal Astronomical broadly, through those he mentored, through his Society (and served a term as its President). He was a influence on United Kingdom astronomy, and the Fellow of the Royal Society for almost half his life; it friendships he forged around the world. 1 Eggen OJ, Lynden-Bell D, Sandage AR (1962) Evidence from the motions of old stars that the Galaxy collapsed. Astrophys J 136:748–766. 2 Lynden-Bell D (1969) Galactic nuclei as collapsed old quasars. Nature 223:690–695. 3 Lynden-Bell D, Chitre SM (2017) Does viscosity turn inflation into the CMB and Λ. arXiv:1707.07566. 2of2 | www.pnas.org/cgi/doi/10.1073/pnas.1803355115 Rees Downloaded by guest on October 2, 2021.