9 ms·

Roger Penrose: Beauty above all

85 points by Hooke 6y ago

mnw21cam 6y ago
Blank page, both directly on the browser, and on outline.com. Anyone have a version that works?
- kgwgk 6y ago
  Roger Penrose: Beauty above all On the life and work of the Nobel Prize-winner, who has revolutionized our understanding of black holes By Graham Farmelo -- Graham Farmelo is a Fellow of Churchill College at the University of Cambridge. His latest book is The Universe Speaks in Numbers (Faber)
  - kgwgk 6y ago
    [1] In 1918, three years after Einstein completed his new theory of gravity, he declared that “the supreme task of the physicist is to arrive at the elementary laws from which the cosmos can be built up by pure deduction”. For the physicists who follow that credo, the most productive sources of inspiration and information in the twentieth century were atoms, the building blocks of matter. In the past few decades, however, the gaze of many of these physicists has turned to outer space, especially to black holes, objects so dense that not even light can escape them. These mysterious objects are proving a fruitful way of addressing the central challenge of fundamental physics: to gain a better understanding of space, time, gravity and even reality itself. Much simpler than atoms, black holes can be regarded as the simplest objects in the universe, made not of matter but only of space and time. This extreme simplicity is a boon to theorists, who have studied these objects in meticulous detail for decades, long before astronomers had observed even one of them through their telescopes. The embarrassment ended in April 2019, when scientists at the Event Horizon Telescope (EHT) published the first image of a black hole, 40 billion kilometres across and 500 million trillion kilometres away. It made news all over the world. At long last, nobody could reasonably argue that black holes were figments of the theorists’ imaginations: these cosmic objects were as real as the stars in the sky. Although several theorists had done excellent work in this field, none of them had been awarded a Nobel Prize. This is probably because the authorities award their prestigious gong only to scientists who have undeniably explained a feature of nature that experimenters have observed. The EHT’s striking image licensed the Nobel physics committee to give their prize this year to the most accomplished black-hole theorists alive (the award is never awarded posthumously). One obvious candidate was Roger Penrose. Many of his peers revere him as the greatest living contributor to the development of Einstein’s theory of gravity, which superseded the account given by Isaac Newton over two centuries before. Penrose introduced new ways of handling Einstein’s theory, using new mathematics that Einstein himself knew nothing about. As a result, Penrose revolutionized the way theorists thought about the theory and applied it to the real world. Most influentially, by using the first of his mathematical theorems relating to the theory, he was first to establish that the existence of black holes is a robust prediction of Einstein’s theory, contrary to the view expressed by many physicists, including Einstein himself. Six weeks after the EHT team published their image, I had a relaxed dinner with Penrose at the Côte Brasserie in Oxford. Over dessert, I could not resist saying how pleased I was that the image of the black hole made him a shoo-in for a Nobel Prize, but he batted the notion away. Happily, he was wrong. At home on the morning of October 6, 2020, the eighty-nine-year-old Penrose climbed out of the shower and took the phone call from Stockholm that most top-tier scientists dream of. He heard that he had received half the prize, and so will receive a cheque for approximately £440,000. The remainder of the prize was shared equally by the astronomers Reinhard Genzel and Andrea Ghez who led the groups that discovered an extremely massive and compact object at the centre of our Milky Way galaxy, an object now widely agreed to be a black hole. This branch of physics has long been dominated by theory rather than experiment, pioneered using pure thought rather than through observations made through telescopes. In the 1770s, John Michell, the rector of Thornhill in Yorkshire and a leading English astronomer, began to imagine “dark stars” from which light could not escape and in 1783 published a paper about them. Thirteen years later, the French mathematician and natural philosopher Pierre-Simon Laplace, sometimes known as the French Newton, set out a similar idea in “Exposition du Système du Monde” and backed it up in a calculation he published in 1799. The concepts of Michell and Laplace attracted little attention among their peers, and for a century remained little more than a curiosity. The first modern analysis of what became known as black holes was written at the University of California, Berkeley, by the American theoretical physicist Robert Oppenheimer and his student Hartland Snyder. They discussed the collapse of heavy stars under their gravity, using the late German physicist Karl Schwarzschild’s solution to the central equation of Einstein’s theory. Published on September 1, 1939, the day the Nazis invaded Poland, the paper received little attention and neither author returned to its theme. An early admirer of Einstein’s theory of gravity was the physicist Max Born, who later described it as “the greatest feat of human thinking about Nature, the most amazing combination of philosophical penetration, physical intuition and mathematical skill”. Yet, for all its brilliance, the theory made little impact on the mainstream in the next thirty-five years. Part of the reason for this was that the basic equations of Einstein’s theory of gravity are formidably difficult to solve and it seemed that their solutions would be only tiny differences to the predictions made by Newton’s theory. The detectors in that era were not sufficiently advanced to test most of these tweaks or test it in some other way. It was only in the early 1950s that interest in gravity theory picked up. Observational astronomers began to develop better detectors and a few theorists gradually began to focus on gravity rather than the forces that shape atoms, governed by the laws of quantum mechanics, a revolutionary theory that European physicists had discovered in the mid-1920s. Anyone who wanted to develop Einstein’s picture of gravity needed to be armed with an abundance of creativity and mathematical skill, as well as a feel for the inner workings of nature that is the hallmark of all exceptional theoretical physicists. Penrose was blessed with all these qualities and had the courage to ignore the tramlines of academia and instead to plough his own furrow in interdisciplinary research. All in all, he was supremely well-equipped to become one of the pioneers of what is often described as the renaissance of gravity theory.
  - kgwgk 6y ago
    [2] The eight-year-old Roger Penrose was not a promising mathematician. He was so slow at mental arithmetic that his school held him back a year. Only after a sympathetic teacher gave him extra time to complete his mathematics tests did Penrose catch up. In those days, he was outshone by his precocious elder brother Oliver, who was a powerful influence on him and later became an accomplished theoretical physicist. Their two younger siblings were also outstandingly talented: their brother Jonathan became a chess grandmaster, their sister Shirley, a professor of cancer genetics. In later life, Roger remembered receiving generous emotional support from his mother and a good deal of intellectual stimulation from his father Lionel, a professor of genetics with a keen interest in mathematics and astronomy. Roger’s mathematical talent began to flower at senior school. He thought about the subject in a distinctive way, not much interested in manipulating symbols, but given to thinking about mathematics geometrically, using his powerful visual imagination. He loved to draw mathematical shapes and make cardboard models of the symmetric geometric shapes known as polyhedra, developing skills he would use later in his career. In the early 1950s, he studied mathematics at University College London, while also cultivating an interest in the cosmos, his interest having been piqued by the popular lectures on BBC radio delivered by Fred Hoyle, a splendidly imaginative astrophysicist and a gifted popularizer. In the spring of 1952, Roger spent a weekend in Cambridge with his brother Oliver, a PhD student, and a friend of one of his roommates, the astrophysicist Dennis Sciama. During a restaurant meal, Oliver introduced his brother to Sciama, who happened to be dining there and sitting nearby. This was to be perhaps the most consequential meeting of Penrose’s life. Dennis Sciama was shaping up to be one of the talented physicists who chose to focus not on this or that phenomenon but on the entire universe – everything that exists. No less important for the scientific community, he had a prodigious generosity of spirit, always seeking to support his colleagues – and, later, his many students – by highlighting research areas that would benefit most from their talents. Sciama saw that Penrose was a thinker of unusual talent and originality, a rare example of a first-class mathematician with the ability to identify key problems in physics and the determination to solve them. Like all mathematicians in the past few centuries, he had a keen eye for symmetry, a quality that had become no less important for theoretical physicists. The main theme of those early conversations between Penrose and Sciama was the nascent discipline of cosmology, the study of the structure and development of the universe, apparently shaped by gravitational forces. Einstein had pioneered modern cosmology using his theory of gravity, which he had developed by generalizing his 1905 special theory of relativity, which modified Newton’s view that space and time are independent concepts. Two years later, the German mathematician Hermann Minkowski introduced the unified concept of space-time, which Einstein used to forge his theory of gravity, which he built from geometric concepts. According to Einstein, space-time can be represented by curved surfaces on which the angles of a triangle do not usually add up to 180 degrees, as they always do on a flat piece of paper. The force of gravity of common experience should be re-interpreted as the curvature of space-time, Einstein argued – not an easy transition for most of us to make. For the geometrically minded Penrose, however, it was a piece of cake. Yet he knew that Einstein’s theory was extremely difficult to apply to the cosmos and therefore to check, mainly because its mathematical structure was so difficult to understand. In the autumn of 1952, Penrose began his PhD at Cambridge, supervised by William Hodge, a top-quality pure mathematician. It was not the happiest of academic relationships for Penrose, because the mathematics Hodge suggested he study was too algebraic, insufficiently geometric. Thrown out by Hodge after only a year, Penrose spent his remaining postgraduate years advised by the more sympathetic John Todd, and finally took his PhD in 1957. During those postgraduate years, Sciama had taken Penrose under his wing, repeatedly urging him, “What are you doing with this pure mathematics nonsense? Come and work on physics and cosmology”. Penrose was not quite ready to take that advice – he was determined to complete his PhD – but chose to moonlight in the world of physics, attending lectures on quantum mechanics by the theoretical physicist Paul Dirac and energetic talks by the cosmologist Hermann Bondi. Inspired by these presentations and won over by the charm and persuasiveness of Sciama, Penrose switched his focus to physics. It was a wise move for him and a hugely productive one for physics. In the early 1960s, the renaissance in gravity theory was well underway, though still a backwater in physics research. Most of its advances were being made by only a few dozen experts. Penrose, then in his early thirties, was rapidly coming to the fore as one of the subject’s most powerful thinkers, well known in the community for his originality and mathematical skill. Urbane, quietly-spoken and unassuming, he was a popular member of the research community, wary of bandwagons and happiest when working alone. He later recalled: “It was important for me always … to think I had a different angle on it from other people. Because I wasn’t good at following where everybody else went”. His methods were delivering such good results that by the early 1960s he had secured a senior faculty appointment at Birkbeck College, London. In the autumn of 1964, he made his most startling and impressive advance, later to win him a Nobel Prize. The story of the discovery began when Sciama suggested that Penrose attend a lecture by the distinguished American theorist David Finkelstein about a controversial aspect of the equations at the heart of Einstein’s theory of gravity. It seemed to some experts that the equations often generated “singularities” tiny regions where the mathematics of the theory goes haywire. The curvature of space-time in these regions becomes not just extremely large but infinite, impossible to deal with using conventional techniques. Other experts believed that the existence of such points in the theory was illusory. The idea that turned out to be crucial to his new way of thinking about these singularities occurred to him when he was crossing a London street, Penrose later recalled. From this epiphany, he developed an innovative way of applying Einstein’s theory to a star imploding under its own gravity to form an object now known as black hole (the term became popular only in 1967, after it was promoted by the physicist John Wheeler, three years after the American journalist Ann Ewing first used it in print). Penrose crystallized his reasoning in the form of a rigorous mathematical theorem that told physicists something new and revealing about the cosmos and our understanding of it: if they used Einstein’s theory to describe any imploding star whatsoever, then the presence of a singularity in the region was not only likely; it was inevitable. In modern language, he had proved that a black hole must contain a singularity.
  - kgwgk 6y ago
    [3] In proving his theorem, Penrose pioneered applications of the branch of mathematics known as topology (from the Greek words topos and logos, meaning “place” and “reason”), a discipline often regarded as part of geometry. But whereas ordinary geometry is about distances, shapes and curvatures, topology is rather different – it is about the ways in which points, curves and surfaces can be connected to each other. A few mathematicians sowed the seeds of the subject in the seventeenth century, but they bore fruit in mainstream mathematics only in the early twentieth century. Theoretical physicists cottoned on to its utility in the real world a few decades later, and began to use it to understand magnetism, the behaviour of particles deep inside atoms and a host of other topics. Penrose was the first to use topology to recast our understanding of gravity. As the American theorist Kip Thorne has pointed out, modern topology explained why there must be an end of space-time somewhere inside a black hole. Penrose demonstrated that singularities are unavoidable features of Einstein’s theory, indicating that the theory contained the seeds of its demise. Ultimately, physicists needed a better, singularity-free theory, though that was much easier said than done. Many of Penrose’s mathematical peers were sceptical of his methods, and many physicists were slow to appreciate his innovations. Predictably, Dennis Sciama immediately grasped their importance and encouraged his group to study them closely. In early 1965, when Penrose gave a talk in Cambridge on his theorem, Sciama made a point of introducing him to his student Stephen Hawking, who was likely to die within months if the diagnosis given to him two years before was correct. Defying the medical odds, Hawking was thriving, exploring Einstein’s theory and learning advanced mathematics, while taking a keen interest in the observations made by astronomers. The Americans Arno Penzias and Robert Wilson made the most impact by detecting radiation that appeared to be the afterglow of a “big bang” billions of years before. This discovery established cosmology as a scientific discipline. Soon, many astronomers – including Sciama and his group – had abandoned the “steady state” picture of the universe and began to espouse the big bang picture. Fred Hoyle was one of the most notable holdouts and usefully put pressure on the new orthodoxy, until his opposition to it became not so much reasoned as cranky. In the final chapter of Hawking’s PhD thesis, he drew on this discovery and on Penrose’s techniques. By extrapolating Penrose’s methods backwards in time, Hawking demonstrated that according to Einstein’s theory of gravity the universe began in an extremely hot and dense state, tying in perfectly with the concept that space and time originated in a big bang. Before long, theoreticians were probing the universe billions of years ago, in the first three minutes of its existence. This was the beginning of one of the epic scientific adventures of the past fifty years. Penrose and Hawking worked separately to study singularities in Einstein’s theory, but joined forces two years later to write their classic account of what became known as the Penrose-Hawking singularity theorems. Having stood on the shoulders of Penrose, Hawking had matured into a world-class theoretical physicist. His greatest discovery, made a few years later, was that black holes are not actually black but continuously emit radiation, a prediction he made by ingeniously jamming together Einstein’s theory of gravity and quantum mechanics. The two theories are quite different, couched in different mathematics, and are notoriously difficult to bring together, let alone to unite. Penrose remained friends with Hawking, but took a different path, working alone on a wide variety of challenges, usually at the interface of mathematics and physics. The relationship between the two disciplines has long fascinated Penrose. In essence, they are both about patterns: mathematics is about patterns of ideas, whereas physics about the underlying order of the universe, the patterns connecting quantities that observers can measure quantitatively. For centuries, mathematics has – in the apt words of the American theorist Eugene Wigner – been “unreasonably effective” in studies of physics. Over the past fifty years, it has become no less clear that research at the frontiers of fundamental physics is unreasonably effective in mathematics. No one fully understands this but, as Penrose has said, it seems to be “no accident”. Among Penrose’s dozens of other contributions to mathematical physics, the most radical is twistor theory, a new approach to fundamental physics. Twistors are mathematical objects – Penrose still calls them his “babies” – from which ordinary space and time emerge as secondary concepts. His approach did not catch on in the physics community, partly because the theory is hard to grasp and is yet to enable physicists to solve a problem that they could not address by more conventional means. Twistors have nonetheless proved useful in several parts of physics, most recently in facilitating a fresh understanding of how fundamental particles scatter off each other. Unconcerned by the unpopularity of his babies, Penrose remains optimistic that they will eventually form the basis of a better understanding of nature via a new perspective on quantum mechanics and Einstein’s theory of gravity. He told me in 2014: “From the word go, I was confident that the idea was too beautiful not to have a place in the great scheme of the natural world”. As do all mathematically-minded researchers in physics, Penrose values above all beauty in a new theory, whether or not it appears at first to account for observations and measurements. In the long run, however, a theory stands or falls by its ability to explain observations and give quantitative agreement with the results of experiments. Penrose has been unimpressed with most of the developments in theoretical physics and cosmology that have caused the most excitement among his peers over the past forty years. One example is string theory, which began to attract a huge following in the mid-1980s. Several of the world’s leading physicists have invested the best years of their working lives in this approach to unifying gravity and the other forces of nature. String theorists achieved impressive results. They shed new light on the structures of mathematical physics and helped to make key discoveries in pure mathematics. Largely as a result of this success, the frontiers of physics and pure mathematics have rarely been more intertwined. Although string theory has not received the support of experiment, it is still the most popular unified framework for understanding the fundamental entities of nature. Penrose is unmoved by this optimism. He believes that because the string framework makes sense only when it is set out in a high number of dimensions, the approach is doomed. Another of his bêtes noires is the idea that the universe expanded briefly at a prodigious rate soon after it began. This concept of cosmic inflation, first proposed around 1980, gives plausible explanations of several observations that were otherwise beyond the ken of astronomers, including the large-scale structure of the universe. Most cosmologists enthusiastically embraced this radical concept, though Penrose thought it was so horrible, and so ugly, that it made him feel ill. In 2016, Penrose set out his views on contemporary theoretical physics in “Fashion, Faith and Fantasy in the New Physics of the Universe”, the most recent of the books he has written for a general audience. None of them is easy reading, but they are all bracingly ambitious. They address big questions – including the nature of consciousness and the nature of reality – and are replete with attractive illustrations that often make even the most obscure arguments palatable.
  - kgwgk 6y ago
    [4] On February 11, 2016, three months after the centenary of Einstein’s theory of gravity, nature disclosed two of its deepest secrets. Astronomers working at the Laser Interferometer Gravitational-Wave Observatory (LIGO) announced that they had verified one of the theory’s signature predictions – the existence of gravitational waves. These waves are ripples in space-time analogous to electromagnetic waves, which constitute light. Fifty years before, this project had been regarded as a scientific moon-shot, and several leading research institutions had steered clear of it, but the gamble had paid off handsomely for its courageous investors, notably the National Science Foundation in the US. The astronomers’ observation was a tour de force of experimentation: using their detector, they measured a physical disturbance that was breathtakingly small, less than a millionth of the width of an atom. According to Einstein’s theory, the measurements indicated that the disturbance had been caused by gravitational waves emitted in a cataclysmic collision over a billion years ago between two black holes, each more massive than two dozen Suns. The “holes” will have merged with such violence that they will have shaken the very fabric of space and time: the astronomers on Earth had observed a minuscule after-effect of the event. The Nobel authorities know an epoch-making scientific discovery when they see one. To no one’s surprise, they awarded their 2017 physics prize to three of the leading lights of the project. They were rewarded for their decisive contributions to the discovery of gravitational waves, but they had also supplied the most compelling evidence yet for black holes. There was plenty of other evidence for these cosmic objects, too, especially the discovery of a massive and compact object at the centre of our galaxy. Although no one had observed a black hole, virtually no scientists were prepared to deny the reality of these elusive objects. The smart money was on the first black holes Nobel Prize going to Roger Penrose and to Stephen Hawking, who dearly wanted to win it, but who died in March 2018. If he had lived only another thirty-one months, he would almost certainly have realized his Nobel dream. Stephen Hawking is one of many physicists who made widely acclaimed contributions to their subject but who died before their work passed the stringent prize criteria set by the Nobel authorities. These days, data from the most ambitious experiments emerge after decades of planning and development – the LIGO project and the latest particle accelerator at CERN are classic cases of this. One consequence is that several world-class theorists fear that their predictions are likely to be testable only after they are dead. For the past forty years, many of the world’s finest theorists have worked on what many of them regard as the central challenge of modern physics: to bring together quantum mechanics and Einstein’s theory of gravity in a way that comprehensively describes all the fundamental particles and forces. Progress is slow, but most leading theorists now believe that the solution will entail a radically new understanding of space and time, and perhaps of reality itself. Black holes emerged long ago as the best laboratory for exploring this programme. The brilliant young black-hole theorist Douglas Stanford put it well recently: “these exotic objects are the ground zero in the war between quantum mechanics and Einstein’s theory of gravity”. Theorists today routinely imagine scenarios around and inside black holes by doing “thought experiments” based on well-established theories, mathematics and intuition. Astronomers will probably not be able to make detailed observations of these objects for several years. In the meantime, it is gratifying that the Nobel authorities have given Roger Penrose their physics prize, the first they have awarded specifically for the modern theory of gravity. (They have rightly given dozens of them for developing and applying quantum mechanics.) Penrose richly deserved the prize. No human mind has done more to enrich our understanding of black holes, the wonderfully simple objects now poised to teach us profound lessons not only about their own space-times but also about the fundamental laws underlying the entire universe.
- MaxBarraclough 6y ago
  Loads up fine for me, perhaps a transient outage? You might want Reader Mode, to strip out the clutter. Annoyingly I found the page doesn't work with Firefox's Reader Mode, but Chromium's copes ok. edit The article mentions beauty exactly twice. It doesn't really deliver on the title.
contravariant 6y ago
Revolutionized our understanding? Before Penrose there was no understanding to revolutionize.
- Koshkin 6y ago
  Also: > the laws of quantum mechanics, a revolutionary theory that European physicists had discovered in the mid-1920s (I think the history of QM discovery spans many years.)
polytely 6y ago
I recently listened to the Penrose episode of the Numberphile podcast, where he is interviewed by Brady Haran, it was quite interesting. https://www.numberphile.com/podcast/roger-penrose https://www.numberphile.com/podcast/roger-penrose
ouid 6y ago
This site doesn't load without enabling javascript, and is a nightmare with javascript enabled.

85 points by Hooke 6y ago

mnw21cam 6y ago

Blank page, both directly on the browser, and on outline.com. Anyone have a version that works?

kgwgk 6y ago
Roger Penrose: Beauty above all On the life and work of the Nobel Prize-winner, who has revolutionized our understanding of black holes By Graham Farmelo -- Graham Farmelo is a Fellow of Churchill College at the University of Cambridge. His latest book is The Universe Speaks in Numbers (Faber)
- kgwgk 6y ago
  [1] In 1918, three years after Einstein completed his new theory of gravity, he declared that “the supreme task of the physicist is to arrive at the elementary laws from which the cosmos can be built up by pure deduction”. For the physicists who follow that credo, the most productive sources of inspiration and information in the twentieth century were atoms, the building blocks of matter. In the past few decades, however, the gaze of many of these physicists has turned to outer space, especially to black holes, objects so dense that not even light can escape them. These mysterious objects are proving a fruitful way of addressing the central challenge of fundamental physics: to gain a better understanding of space, time, gravity and even reality itself. Much simpler than atoms, black holes can be regarded as the simplest objects in the universe, made not of matter but only of space and time. This extreme simplicity is a boon to theorists, who have studied these objects in meticulous detail for decades, long before astronomers had observed even one of them through their telescopes. The embarrassment ended in April 2019, when scientists at the Event Horizon Telescope (EHT) published the first image of a black hole, 40 billion kilometres across and 500 million trillion kilometres away. It made news all over the world. At long last, nobody could reasonably argue that black holes were figments of the theorists’ imaginations: these cosmic objects were as real as the stars in the sky. Although several theorists had done excellent work in this field, none of them had been awarded a Nobel Prize. This is probably because the authorities award their prestigious gong only to scientists who have undeniably explained a feature of nature that experimenters have observed. The EHT’s striking image licensed the Nobel physics committee to give their prize this year to the most accomplished black-hole theorists alive (the award is never awarded posthumously). One obvious candidate was Roger Penrose. Many of his peers revere him as the greatest living contributor to the development of Einstein’s theory of gravity, which superseded the account given by Isaac Newton over two centuries before. Penrose introduced new ways of handling Einstein’s theory, using new mathematics that Einstein himself knew nothing about. As a result, Penrose revolutionized the way theorists thought about the theory and applied it to the real world. Most influentially, by using the first of his mathematical theorems relating to the theory, he was first to establish that the existence of black holes is a robust prediction of Einstein’s theory, contrary to the view expressed by many physicists, including Einstein himself. Six weeks after the EHT team published their image, I had a relaxed dinner with Penrose at the Côte Brasserie in Oxford. Over dessert, I could not resist saying how pleased I was that the image of the black hole made him a shoo-in for a Nobel Prize, but he batted the notion away. Happily, he was wrong. At home on the morning of October 6, 2020, the eighty-nine-year-old Penrose climbed out of the shower and took the phone call from Stockholm that most top-tier scientists dream of. He heard that he had received half the prize, and so will receive a cheque for approximately £440,000. The remainder of the prize was shared equally by the astronomers Reinhard Genzel and Andrea Ghez who led the groups that discovered an extremely massive and compact object at the centre of our Milky Way galaxy, an object now widely agreed to be a black hole. This branch of physics has long been dominated by theory rather than experiment, pioneered using pure thought rather than through observations made through telescopes. In the 1770s, John Michell, the rector of Thornhill in Yorkshire and a leading English astronomer, began to imagine “dark stars” from which light could not escape and in 1783 published a paper about them. Thirteen years later, the French mathematician and natural philosopher Pierre-Simon Laplace, sometimes known as the French Newton, set out a similar idea in “Exposition du Système du Monde” and backed it up in a calculation he published in 1799. The concepts of Michell and Laplace attracted little attention among their peers, and for a century remained little more than a curiosity. The first modern analysis of what became known as black holes was written at the University of California, Berkeley, by the American theoretical physicist Robert Oppenheimer and his student Hartland Snyder. They discussed the collapse of heavy stars under their gravity, using the late German physicist Karl Schwarzschild’s solution to the central equation of Einstein’s theory. Published on September 1, 1939, the day the Nazis invaded Poland, the paper received little attention and neither author returned to its theme. An early admirer of Einstein’s theory of gravity was the physicist Max Born, who later described it as “the greatest feat of human thinking about Nature, the most amazing combination of philosophical penetration, physical intuition and mathematical skill”. Yet, for all its brilliance, the theory made little impact on the mainstream in the next thirty-five years. Part of the reason for this was that the basic equations of Einstein’s theory of gravity are formidably difficult to solve and it seemed that their solutions would be only tiny differences to the predictions made by Newton’s theory. The detectors in that era were not sufficiently advanced to test most of these tweaks or test it in some other way. It was only in the early 1950s that interest in gravity theory picked up. Observational astronomers began to develop better detectors and a few theorists gradually began to focus on gravity rather than the forces that shape atoms, governed by the laws of quantum mechanics, a revolutionary theory that European physicists had discovered in the mid-1920s. Anyone who wanted to develop Einstein’s picture of gravity needed to be armed with an abundance of creativity and mathematical skill, as well as a feel for the inner workings of nature that is the hallmark of all exceptional theoretical physicists. Penrose was blessed with all these qualities and had the courage to ignore the tramlines of academia and instead to plough his own furrow in interdisciplinary research. All in all, he was supremely well-equipped to become one of the pioneers of what is often described as the renaissance of gravity theory.
- kgwgk 6y ago
  [2] The eight-year-old Roger Penrose was not a promising mathematician. He was so slow at mental arithmetic that his school held him back a year. Only after a sympathetic teacher gave him extra time to complete his mathematics tests did Penrose catch up. In those days, he was outshone by his precocious elder brother Oliver, who was a powerful influence on him and later became an accomplished theoretical physicist. Their two younger siblings were also outstandingly talented: their brother Jonathan became a chess grandmaster, their sister Shirley, a professor of cancer genetics. In later life, Roger remembered receiving generous emotional support from his mother and a good deal of intellectual stimulation from his father Lionel, a professor of genetics with a keen interest in mathematics and astronomy. Roger’s mathematical talent began to flower at senior school. He thought about the subject in a distinctive way, not much interested in manipulating symbols, but given to thinking about mathematics geometrically, using his powerful visual imagination. He loved to draw mathematical shapes and make cardboard models of the symmetric geometric shapes known as polyhedra, developing skills he would use later in his career. In the early 1950s, he studied mathematics at University College London, while also cultivating an interest in the cosmos, his interest having been piqued by the popular lectures on BBC radio delivered by Fred Hoyle, a splendidly imaginative astrophysicist and a gifted popularizer. In the spring of 1952, Roger spent a weekend in Cambridge with his brother Oliver, a PhD student, and a friend of one of his roommates, the astrophysicist Dennis Sciama. During a restaurant meal, Oliver introduced his brother to Sciama, who happened to be dining there and sitting nearby. This was to be perhaps the most consequential meeting of Penrose’s life. Dennis Sciama was shaping up to be one of the talented physicists who chose to focus not on this or that phenomenon but on the entire universe – everything that exists. No less important for the scientific community, he had a prodigious generosity of spirit, always seeking to support his colleagues – and, later, his many students – by highlighting research areas that would benefit most from their talents. Sciama saw that Penrose was a thinker of unusual talent and originality, a rare example of a first-class mathematician with the ability to identify key problems in physics and the determination to solve them. Like all mathematicians in the past few centuries, he had a keen eye for symmetry, a quality that had become no less important for theoretical physicists. The main theme of those early conversations between Penrose and Sciama was the nascent discipline of cosmology, the study of the structure and development of the universe, apparently shaped by gravitational forces. Einstein had pioneered modern cosmology using his theory of gravity, which he had developed by generalizing his 1905 special theory of relativity, which modified Newton’s view that space and time are independent concepts. Two years later, the German mathematician Hermann Minkowski introduced the unified concept of space-time, which Einstein used to forge his theory of gravity, which he built from geometric concepts. According to Einstein, space-time can be represented by curved surfaces on which the angles of a triangle do not usually add up to 180 degrees, as they always do on a flat piece of paper. The force of gravity of common experience should be re-interpreted as the curvature of space-time, Einstein argued – not an easy transition for most of us to make. For the geometrically minded Penrose, however, it was a piece of cake. Yet he knew that Einstein’s theory was extremely difficult to apply to the cosmos and therefore to check, mainly because its mathematical structure was so difficult to understand. In the autumn of 1952, Penrose began his PhD at Cambridge, supervised by William Hodge, a top-quality pure mathematician. It was not the happiest of academic relationships for Penrose, because the mathematics Hodge suggested he study was too algebraic, insufficiently geometric. Thrown out by Hodge after only a year, Penrose spent his remaining postgraduate years advised by the more sympathetic John Todd, and finally took his PhD in 1957. During those postgraduate years, Sciama had taken Penrose under his wing, repeatedly urging him, “What are you doing with this pure mathematics nonsense? Come and work on physics and cosmology”. Penrose was not quite ready to take that advice – he was determined to complete his PhD – but chose to moonlight in the world of physics, attending lectures on quantum mechanics by the theoretical physicist Paul Dirac and energetic talks by the cosmologist Hermann Bondi. Inspired by these presentations and won over by the charm and persuasiveness of Sciama, Penrose switched his focus to physics. It was a wise move for him and a hugely productive one for physics. In the early 1960s, the renaissance in gravity theory was well underway, though still a backwater in physics research. Most of its advances were being made by only a few dozen experts. Penrose, then in his early thirties, was rapidly coming to the fore as one of the subject’s most powerful thinkers, well known in the community for his originality and mathematical skill. Urbane, quietly-spoken and unassuming, he was a popular member of the research community, wary of bandwagons and happiest when working alone. He later recalled: “It was important for me always … to think I had a different angle on it from other people. Because I wasn’t good at following where everybody else went”. His methods were delivering such good results that by the early 1960s he had secured a senior faculty appointment at Birkbeck College, London. In the autumn of 1964, he made his most startling and impressive advance, later to win him a Nobel Prize. The story of the discovery began when Sciama suggested that Penrose attend a lecture by the distinguished American theorist David Finkelstein about a controversial aspect of the equations at the heart of Einstein’s theory of gravity. It seemed to some experts that the equations often generated “singularities” tiny regions where the mathematics of the theory goes haywire. The curvature of space-time in these regions becomes not just extremely large but infinite, impossible to deal with using conventional techniques. Other experts believed that the existence of such points in the theory was illusory. The idea that turned out to be crucial to his new way of thinking about these singularities occurred to him when he was crossing a London street, Penrose later recalled. From this epiphany, he developed an innovative way of applying Einstein’s theory to a star imploding under its own gravity to form an object now known as black hole (the term became popular only in 1967, after it was promoted by the physicist John Wheeler, three years after the American journalist Ann Ewing first used it in print). Penrose crystallized his reasoning in the form of a rigorous mathematical theorem that told physicists something new and revealing about the cosmos and our understanding of it: if they used Einstein’s theory to describe any imploding star whatsoever, then the presence of a singularity in the region was not only likely; it was inevitable. In modern language, he had proved that a black hole must contain a singularity.
- kgwgk 6y ago
  [3] In proving his theorem, Penrose pioneered applications of the branch of mathematics known as topology (from the Greek words topos and logos, meaning “place” and “reason”), a discipline often regarded as part of geometry. But whereas ordinary geometry is about distances, shapes and curvatures, topology is rather different – it is about the ways in which points, curves and surfaces can be connected to each other. A few mathematicians sowed the seeds of the subject in the seventeenth century, but they bore fruit in mainstream mathematics only in the early twentieth century. Theoretical physicists cottoned on to its utility in the real world a few decades later, and began to use it to understand magnetism, the behaviour of particles deep inside atoms and a host of other topics. Penrose was the first to use topology to recast our understanding of gravity. As the American theorist Kip Thorne has pointed out, modern topology explained why there must be an end of space-time somewhere inside a black hole. Penrose demonstrated that singularities are unavoidable features of Einstein’s theory, indicating that the theory contained the seeds of its demise. Ultimately, physicists needed a better, singularity-free theory, though that was much easier said than done. Many of Penrose’s mathematical peers were sceptical of his methods, and many physicists were slow to appreciate his innovations. Predictably, Dennis Sciama immediately grasped their importance and encouraged his group to study them closely. In early 1965, when Penrose gave a talk in Cambridge on his theorem, Sciama made a point of introducing him to his student Stephen Hawking, who was likely to die within months if the diagnosis given to him two years before was correct. Defying the medical odds, Hawking was thriving, exploring Einstein’s theory and learning advanced mathematics, while taking a keen interest in the observations made by astronomers. The Americans Arno Penzias and Robert Wilson made the most impact by detecting radiation that appeared to be the afterglow of a “big bang” billions of years before. This discovery established cosmology as a scientific discipline. Soon, many astronomers – including Sciama and his group – had abandoned the “steady state” picture of the universe and began to espouse the big bang picture. Fred Hoyle was one of the most notable holdouts and usefully put pressure on the new orthodoxy, until his opposition to it became not so much reasoned as cranky. In the final chapter of Hawking’s PhD thesis, he drew on this discovery and on Penrose’s techniques. By extrapolating Penrose’s methods backwards in time, Hawking demonstrated that according to Einstein’s theory of gravity the universe began in an extremely hot and dense state, tying in perfectly with the concept that space and time originated in a big bang. Before long, theoreticians were probing the universe billions of years ago, in the first three minutes of its existence. This was the beginning of one of the epic scientific adventures of the past fifty years. Penrose and Hawking worked separately to study singularities in Einstein’s theory, but joined forces two years later to write their classic account of what became known as the Penrose-Hawking singularity theorems. Having stood on the shoulders of Penrose, Hawking had matured into a world-class theoretical physicist. His greatest discovery, made a few years later, was that black holes are not actually black but continuously emit radiation, a prediction he made by ingeniously jamming together Einstein’s theory of gravity and quantum mechanics. The two theories are quite different, couched in different mathematics, and are notoriously difficult to bring together, let alone to unite. Penrose remained friends with Hawking, but took a different path, working alone on a wide variety of challenges, usually at the interface of mathematics and physics. The relationship between the two disciplines has long fascinated Penrose. In essence, they are both about patterns: mathematics is about patterns of ideas, whereas physics about the underlying order of the universe, the patterns connecting quantities that observers can measure quantitatively. For centuries, mathematics has – in the apt words of the American theorist Eugene Wigner – been “unreasonably effective” in studies of physics. Over the past fifty years, it has become no less clear that research at the frontiers of fundamental physics is unreasonably effective in mathematics. No one fully understands this but, as Penrose has said, it seems to be “no accident”. Among Penrose’s dozens of other contributions to mathematical physics, the most radical is twistor theory, a new approach to fundamental physics. Twistors are mathematical objects – Penrose still calls them his “babies” – from which ordinary space and time emerge as secondary concepts. His approach did not catch on in the physics community, partly because the theory is hard to grasp and is yet to enable physicists to solve a problem that they could not address by more conventional means. Twistors have nonetheless proved useful in several parts of physics, most recently in facilitating a fresh understanding of how fundamental particles scatter off each other. Unconcerned by the unpopularity of his babies, Penrose remains optimistic that they will eventually form the basis of a better understanding of nature via a new perspective on quantum mechanics and Einstein’s theory of gravity. He told me in 2014: “From the word go, I was confident that the idea was too beautiful not to have a place in the great scheme of the natural world”. As do all mathematically-minded researchers in physics, Penrose values above all beauty in a new theory, whether or not it appears at first to account for observations and measurements. In the long run, however, a theory stands or falls by its ability to explain observations and give quantitative agreement with the results of experiments. Penrose has been unimpressed with most of the developments in theoretical physics and cosmology that have caused the most excitement among his peers over the past forty years. One example is string theory, which began to attract a huge following in the mid-1980s. Several of the world’s leading physicists have invested the best years of their working lives in this approach to unifying gravity and the other forces of nature. String theorists achieved impressive results. They shed new light on the structures of mathematical physics and helped to make key discoveries in pure mathematics. Largely as a result of this success, the frontiers of physics and pure mathematics have rarely been more intertwined. Although string theory has not received the support of experiment, it is still the most popular unified framework for understanding the fundamental entities of nature. Penrose is unmoved by this optimism. He believes that because the string framework makes sense only when it is set out in a high number of dimensions, the approach is doomed. Another of his bêtes noires is the idea that the universe expanded briefly at a prodigious rate soon after it began. This concept of cosmic inflation, first proposed around 1980, gives plausible explanations of several observations that were otherwise beyond the ken of astronomers, including the large-scale structure of the universe. Most cosmologists enthusiastically embraced this radical concept, though Penrose thought it was so horrible, and so ugly, that it made him feel ill. In 2016, Penrose set out his views on contemporary theoretical physics in “Fashion, Faith and Fantasy in the New Physics of the Universe”, the most recent of the books he has written for a general audience. None of them is easy reading, but they are all bracingly ambitious. They address big questions – including the nature of consciousness and the nature of reality – and are replete with attractive illustrations that often make even the most obscure arguments palatable.
- kgwgk 6y ago
  [4] On February 11, 2016, three months after the centenary of Einstein’s theory of gravity, nature disclosed two of its deepest secrets. Astronomers working at the Laser Interferometer Gravitational-Wave Observatory (LIGO) announced that they had verified one of the theory’s signature predictions – the existence of gravitational waves. These waves are ripples in space-time analogous to electromagnetic waves, which constitute light. Fifty years before, this project had been regarded as a scientific moon-shot, and several leading research institutions had steered clear of it, but the gamble had paid off handsomely for its courageous investors, notably the National Science Foundation in the US. The astronomers’ observation was a tour de force of experimentation: using their detector, they measured a physical disturbance that was breathtakingly small, less than a millionth of the width of an atom. According to Einstein’s theory, the measurements indicated that the disturbance had been caused by gravitational waves emitted in a cataclysmic collision over a billion years ago between two black holes, each more massive than two dozen Suns. The “holes” will have merged with such violence that they will have shaken the very fabric of space and time: the astronomers on Earth had observed a minuscule after-effect of the event. The Nobel authorities know an epoch-making scientific discovery when they see one. To no one’s surprise, they awarded their 2017 physics prize to three of the leading lights of the project. They were rewarded for their decisive contributions to the discovery of gravitational waves, but they had also supplied the most compelling evidence yet for black holes. There was plenty of other evidence for these cosmic objects, too, especially the discovery of a massive and compact object at the centre of our galaxy. Although no one had observed a black hole, virtually no scientists were prepared to deny the reality of these elusive objects. The smart money was on the first black holes Nobel Prize going to Roger Penrose and to Stephen Hawking, who dearly wanted to win it, but who died in March 2018. If he had lived only another thirty-one months, he would almost certainly have realized his Nobel dream. Stephen Hawking is one of many physicists who made widely acclaimed contributions to their subject but who died before their work passed the stringent prize criteria set by the Nobel authorities. These days, data from the most ambitious experiments emerge after decades of planning and development – the LIGO project and the latest particle accelerator at CERN are classic cases of this. One consequence is that several world-class theorists fear that their predictions are likely to be testable only after they are dead. For the past forty years, many of the world’s finest theorists have worked on what many of them regard as the central challenge of modern physics: to bring together quantum mechanics and Einstein’s theory of gravity in a way that comprehensively describes all the fundamental particles and forces. Progress is slow, but most leading theorists now believe that the solution will entail a radically new understanding of space and time, and perhaps of reality itself. Black holes emerged long ago as the best laboratory for exploring this programme. The brilliant young black-hole theorist Douglas Stanford put it well recently: “these exotic objects are the ground zero in the war between quantum mechanics and Einstein’s theory of gravity”. Theorists today routinely imagine scenarios around and inside black holes by doing “thought experiments” based on well-established theories, mathematics and intuition. Astronomers will probably not be able to make detailed observations of these objects for several years. In the meantime, it is gratifying that the Nobel authorities have given Roger Penrose their physics prize, the first they have awarded specifically for the modern theory of gravity. (They have rightly given dozens of them for developing and applying quantum mechanics.) Penrose richly deserved the prize. No human mind has done more to enrich our understanding of black holes, the wonderfully simple objects now poised to teach us profound lessons not only about their own space-times but also about the fundamental laws underlying the entire universe.
MaxBarraclough 6y ago
Loads up fine for me, perhaps a transient outage? You might want Reader Mode, to strip out the clutter. Annoyingly I found the page doesn't work with Firefox's Reader Mode, but Chromium's copes ok. edit The article mentions beauty exactly twice. It doesn't really deliver on the title.

contravariant 6y ago

Revolutionized our understanding? Before Penrose there was no understanding to revolutionize.

Koshkin 6y ago
Also: > the laws of quantum mechanics, a revolutionary theory that European physicists had discovered in the mid-1920s (I think the history of QM discovery spans many years.)

polytely 6y ago

I recently listened to the Penrose episode of the Numberphile podcast, where he is interviewed by Brady Haran, it was quite interesting. https://www.numberphile.com/podcast/roger-penrose https://www.numberphile.com/podcast/roger-penrose

ouid 6y ago

This site doesn't load without enabling javascript, and is a nightmare with javascript enabled.