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Roger Penrose

 
Scientist: Sir Roger Penrose

British mathematician and theoretical physicist (1931–)

Penrose, the son of the geneticist Lionel Penrose, was born at Colchester in Essex. He graduated from University College, London, and obtained his PhD in 1957 from Cambridge University. After holding various lecturing and research posts in London, Cambridge, and in America at Princeton, Syracuse, and Texas, Penrose was appointed professor of applied mathematics at Birkbeck College, London, in 1966. In 1973 he was elected Rouse Ball Professor of Mathematics at Oxford.

Penrose has done much to elucidate the fundamental properties of black holes. These result from the total gravitational collapse of large stars that shrink to such a small volume that not even a light signal can escape from them. There is thus a boundary around a black hole inside which all information about the black hole is trapped; this is known as its ‘event horizon’. With Stephen Hawking, Penrose proved a theorem of Einstein's general relativity asserting that at the center of a black hole there must evolve a ‘space–time singularity’ of zero volume and infinite density where the present laws of physics break down. He went on to propose his hypothesis of ‘cosmic censorship’, that such singularities cannot be ‘naked’; they must possess an event horizon. The effect of this would be to conceal and isolate the singularity with its indifference to the laws of physics.

Despite this Penrose went on in 1969 to describe a mechanism for the extraction of energy from a Kerr black hole, an uncharged rotating body first described by Roy Kerr in 1963. Such bodies are surrounded by an ergosphere within which it is impossible for an object to be at rest. If, Penrose demonstrated, a body fell into this area it would split into two particles; one would fall into the hole and the other would escape with more mass-energy than the initial particle. In this way rotational energy of the black hole is transferred to the particle outside the hole.

From the mid-1960s Penrose has been working on the development of a new cosmology based on a complex geometry. Penrose began with ‘twistors’ – massless objects with both linear and angular momentum in twistor space. From these he attempted to reconstruct the main outlines of modern physics. The matter is pursued not only by Penrose but through a number of ‘twistor groups’ who communicate through a Twistor Newsletter. The fullest account of twistor theory is to be found in Spinors and Space-Time (2 vols., 1984–86) by Penrose and W. Windler.

In 1974 Penrose introduced a novel tiling of the affine plane (Penrose tiling). Periodic tilings in which a unit figure is endlessly repeated can be constructed from triangles, squares, and hexagons – figures with three-, four-, or six-fold symmetry. The plane cannot be tiled by pentagons, which have a five-fold symmetry; three pentagons fitted together always leave a crack, known to crystallographers as a ‘frustration’. It was also known that crystal structures could have two-, three-, four-, or six-fold rotational symmetries only. No crystal, that is, could have a five-fold rotational symmetry.

Penrose's method of tiling the plane involved constructing two rhombuses by dividing the diagonal of a regular parallelogram by a golden section. These could be combined according to simple rules so as to cover the plane, even though there was no simple repeated unit cell. The rhombuses can be assembled in such a way as to have an almost five-fold symmetry. As such they were seen as an interesting oddity, usually discussed in columns devoted to recreational mathematics. However, things changed dramatically in 1984 when Dany Schectman of the National Bureau of Standards and his colleagues found that a rapidly cooled sample of an aluminum–manganese alloy formed crystals that displayed a five-fold symmetry. ‘Quasicrystals’, as they soon became known, developed rapidly into a major new research field and became the subject of hundreds of papers.

In addition to continuing his work on twistor theory Penrose also published a widely read book, The Emperor's New Mind (1989). The book is an attack on aspects of artificial intelligence. In it he argues that there are aspects of mathematics that cannot be tied to a set of rules. We cannot allow “one universally formal system…equivalent to all the mathematicians' algorithms for judging mathematical truth.” Such a system would violate Gödel's theorem. Nor can we accept that algorithms used are so complicated and obscure that their validity can never be known. We do not in fact ascertain mathematical truth solely through the use of algorithms. “We must see the truth of a mathematical argument to be convinced of its validity,” Penrose has insisted. Consequently when we see the validity of a theorem, in seeing it “we reveal the very nonalgorithmic nature of the ‘seeing’ process itself.”

He further developed his arguments in Shadows of the Mind (1994), in which he also answered many of the objections raised against the earlier work. Penrose has also published (in collaboration with Stephen Hawking) The Nature of Space and Time (1996), in which they develop their own cosmological viewpoints. Thus while Penrose presents his own twistor view of the universe, Hawking concentrates on problems connected with quantum cosmology.

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Biography: Roger Penrose
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The British mathematician and physicist, Sir Roger Penrose (born 1931), made striking and original contributions to the study of geometry, relativity, quantum mechanics, and the human mind.

Roger Penrose was born in Colchester, England, on August 8, 1931. His father was the geneticist Lionel Penrose, an expert on mental defects, whose interest in geometry was communicated to his son. The Penrose family was illustrious in British intellectual life in the 20th century. Jonathan Penrose won the British chess championship ten times in the 1950s and 1960s. It is not surprising that the intellectual life of the Penrose household was lively.

Penrose received his undergraduate degree from University College, London, and then proceeded to Cambridge for his doctorate. While an undergraduate he discovered a theorem concerning conic sections from which some of the basic theorems of projective geometry follow as special cases. As part of his work for his doctorate he rediscovered some important results in the theory of matrices. From 1964 to 1966 he was a reader in applied mathematics at Birkbeck College at the University of London, advancing to full professor in 1966.

The study of mathematics in Britain has always included a large amount of applied mathematics and even physics, so it is not unexpected that much of Penrose's best-known work looks more like physics than pure mathematics. He and Stephen Hawking studied black holes in collaboration and the two of them identified the basic characteristics of black holes, which result from the collapse of large stars. The mass becomes so concentrated that even photons (light particles) are unable to escape. As a result, even if it is possible to recognize the existence of a black hole from its effects on nearby objects, it would be impossible to observe the interior of the black hole itself.

Starting from his interest in the question of whether space and time are smooth or divided into discrete units, Penrose investigated many aspects of quantum mechanics. While he was at Cambridge, Penrose tried to build mathematical models for quantum mechanics using the basic elements of real numbers. One of the long-standing problems of 20th-century physics has been to combine the apparently conflicting fields of relativity and quantum mechanics. Penrose attempted to find a resolution via twistor geometry, which is based on complex numbers. This ambitious project remains far from completion, but the study of twistors has become an industry within physics in its own right.

Penrose collaborated with his father on the creation of a visual illusion that was incorporated into lithographs by the Dutch artist M. C. Escher, whose work included many mathematical elements. Also within the area of geometry, Penrose made a striking contribution to the study of tilings. A tiling is a method of covering the entire plane with polygons, for example squares or equilateral triangles. Tilings using those figures are called periodic because the pattern repeats regularly in moving about the plane. The question was whether it would be possible to tile (cover) the plane with a nonrepeating pattern.

Before Penrose made his contribution, others had already shown that it was possible to tile the plane in a nonperiodic fashion. The first solution used an immense number of different tiles, and the best solution known in 1974 still used six tiles of different shapes. In that year Penrose found a nonperiodic tiling using only two different shapes. Although this geometric contribution seems far removed from his studies of astrophysics and quantum mechanics, it also reflects the width of his scientific background.

In 1966 Penrose received the Adams Prize from Cambridge University and in 1971 the Dannie Heineman Prize for Physics from the American Physical Society. The next year he was elected to the Royal Society and in 1973 he succeeded to the prestigious Rouse Ball Chair of Mathematics at Oxford University. He shared two awards with his collaborator Stephen Hawking; the 1975 Royal Astronomical Society's Eddington Medal and the 1988 Wolf Prize for physics. Penrose held visiting positions at many leading universities in the United States including Cornell, Texas, California, and Princeton.

Penrose became known to the general public thanks to the best-selling book The Emperor's New Mind, which appeared on both sides of the Atlantic in 1989. Hawking had written a book to similar acclaim a couple of years before but had not tried to include any equations other than Einstein's e = mc2. Penrose's book includes that equation and hundreds of others as it ranges over computers, minds, and the laws of physics, to mention just the subjects explicitly named in the subtitle. The Emperor's New Mind may have been the best book about modern science yet written. Within 18 months it had run through numerous printings.

During a historic lecture series at the Isaac Newton Institute for Mathematical Sciences at Cambridge University in 1994, Penrose and Hawking recreated the famous Bohr-Einstein debate. In public lectures Penrose and Hawking presented their distinctive views on the universe, its evolution and impact on quantum theory. The same year, Penrose was knighted for his numerous contributions to science. Shadows of the Mind (1994) once again demonstrated the ability of Penrose to communicate complex theoretical physics to a general audience.

What distinguished Roger Penrose among the physicists and mathematicians of his time was the breadth and depth in his work. Some of the essays that he wrote illustrate the attention that he gave to his intellectual ancestors, such as Sir Isaac Newton. His influence on his students was profound.

Further Reading

There is an article on Penrose in the McGraw-Hill set on Modern Scientists and Engineers (1980). A more personal glimpse is available in Martin Gardner's introduction to Penrose's The Emperor's New Mind (1989). A good discussion of tilings and Penrose's work is in B. Grunbaum and G. Shephard's book Tilings and Patterns (1986). Articles on Penrose can be found in the popular science journals Scientific American and Science. An account of the 1994 Penrose-Hawking debate is presented in The Nature of Space and Time (1996).

Wikipedia: Roger Penrose
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Sir Roger Penrose

Roger Penrose at Brookhaven Lab, 6 February 2007.
Born 8 August 1931 (1931-08-08) (age 78)
Colchester, Essex, England
Residence United Kingdom
Canada (During WWII)
Nationality British
Fields Mathematical physicist
Institutions Bedford College, London
St John's College, Cambridge
Princeton University
Syracuse University
King’s College, London
Birkbeck, University of London
University of Oxford
Alma mater University of Cambridge
University College London
University College School
Doctoral advisor John A. Todd
Other academic advisors William Hodge
Doctoral students Tristan Needham
Richard Jozsa
Richard Ward
Andrew Hodges
George Burnett-Stuart
Matthew Ginsberg
Adam Helfer
Lane P. Hughston
Peter Law
Claude LeBrun
Ross Moore
Duncan Stone
Tim Poston
George Sparling
K. Paul Tod
Known for Penrose tiling
Twistor Theory
Geometry of spacetime

Cosmic censorship
Weyl curvature hypothesis

Moore-Penrose pseudoinverse
Newman-Penrose formalism
Penrose stairs
Penrose inequalities
Orch-OR
Influences Dennis W. Sciama
Influenced Michael Atiyah
Stuart Hameroff
Notable awards Wolf Prize (1988)
Dirac Medal (1989)
Copley Medal (2008)
Religious stance Materialist[1] Platonist[2] with no doctrinal stance[3]
Signature
Notes
He is the brother of Jonathan Penrose and Oliver Penrose, and son of Lionel Penrose. He is the nephew of Roland Penrose.

Sir Roger Penrose, OM, FRS (born 8 August 1931) is an English mathematical physicist and Emeritus Rouse Ball Professor of Mathematics at the Mathematical Institute, University of Oxford and Emeritus Fellow of Wadham College. He has received a number of prizes and awards, including the 1988 Wolf Prize for physics which he shared with Stephen Hawking for their contribution to our understanding of the universe[4]. He is renowned for his work in mathematical physics, in particular his contributions to general relativity and cosmology. He is also a recreational mathematician and philosopher.

Contents

Career

Born in Colchester, Essex, England, Roger Penrose is a son of Lionel S. Penrose and Margaret Leathes.[5] Penrose is the brother of mathematician Oliver Penrose and correspondence chess grandmaster Jonathan Penrose. Penrose was precocious as a child.[6] He attended University College School. Penrose graduated with a first class degree in mathematics from University College London. In 1955, while still a student, Penrose reinvented the generalized matrix inverse (also known as Moore-Penrose inverse, (see Penrose, R. 'A Generalized Inverse for Matrices.' Proc. Cambridge Phil. Soc. 51, 406-413, 1955). Penrose earned his Ph.D. at Cambridge (St John's College) in 1958, writing a thesis on 'tensor methods in algebraic geometry' under algebraist and geometer John A. Todd. He devised and popularised the Penrose triangle in the 1950s, describing it as "impossibility in its purest form" and exchanged material with the artist M. C. Escher, whose earlier depictions of impossible objects partly inspired it. In 1965 at Cambridge, Penrose proved that singularities (such as black holes) could be formed from the gravitational collapse of immense, dying stars (Ferguson, 1991: 66).

Oil painting by Urs Schmid (1995) of a Penrose tiling using fat and thin rhombus.

In 1967, Penrose invented the twistor theory which maps geometric objects in Minkowski space into the 4-dimensional complex space with the metric signature (2,2). In 1969 he conjectured the cosmic censorship hypothesis. This proposes (rather informally) that the universe protects us from the inherent unpredictability of singularities (such as the one in the centre of a black hole) by hiding them from our view behind an event horizon. This form is now known as the "weak censorship hypothesis"; in 1979, Penrose formulated a stronger version called the "strong censorship hypothesis". Together with the BKL conjecture and issues of nonlinear stability, settling the censorship conjectures is one of the most important outstanding problems in general relativity. Also from 1979 dates Penrose's influential Weyl curvature hypothesis on the initial conditions of the observable part of the Universe and the origin of the second law of thermodynamics.[7] Penrose wrote a paper on the Terrell rotation.

Roger Penrose is well known for his 1974 discovery of Penrose tilings, which are formed from two tiles that can only tile the plane nonperiodically, and are the first tilings to exhibit fivefold rotational symmetry. Penrose developed these ideas from the article Deux types fondamentaux de distribution statistique[8] (1938; an English translation Two Basic Types of Statistical Distribution) of Czech geographer, demographer and statistician Jaromír Korčák. In 1984, such patterns were observed in the arrangement of atoms in quasicrystals. Another noteworthy contribution is his 1971 invention of spin networks, which later came to form the geometry of spacetime in loop quantum gravity. He was influential in popularizing what are commonly known as Penrose diagrams (causal diagrams). In 2004 Penrose released The Road to Reality: A Complete Guide to the Laws of the Universe, a 1,099-page book aimed at giving a comprehensive guide to the laws of physics. He has proposed a novel interpretation of quantum mechanics.[9] Penrose is the Francis and Helen Pentz Distinguished (visiting) Professor of Physics and Mathematics at Pennsylvania State University.[10]

Penrose is married to Vanessa Thomas, with whom he has one child. He has three sons from a previous marriage to American Joan Isabel Wedge (1959).

Physics and consciousness

Penrose has written controversial books on the connection between fundamental physics and human (or animal) consciousness. In The Emperor's New Mind (1989), he argues that known laws of physics are inadequate to explain the phenomenon of consciousness. Penrose hints at the characteristics this new physics may have and specifies the requirements for a bridge between classical and quantum mechanics (what he terms correct quantum gravity, CQG). He claims that the present computer is unable to have intelligence because it is an algorithmically deterministic system. He argues against the viewpoint that the rational processes of the mind are completely algorithmic and can thus be duplicated by a sufficiently complex computer—this is in contrast to views, e.g., artificial intelligence, that thought can be simulated. Penrose notes that a process can conceivably be deterministic without being algorithmic. This is based on claims that consciousness transcends formal logic systems because things such as the insolubility of the halting problem and Gödel's incompleteness theorem restrict an algorithmically based logic from traits such as mathematical insight. Penrose believes that such deterministic non-algorithmic processes may come in play in the quantum mechanical wave function reduction, and may be harnessed by the brain. These claims were originally made by the philosopher John Lucas of Merton College, Oxford.

In 1994, Penrose followed up The Emperor's New Mind with Shadows of the Mind and in 1997 with The Large, the Small and the Human Mind, further updating and expanding his theories. Penrose's views on the human thought process are not widely accepted in scientific circles. According to Marvin Minsky, because people can construe false ideas to be factual, the process of thinking is not limited to formal logic. Furthermore, he says that artificial intelligence (AI) programs can also conclude that false statements are true, so error is not unique to humans.

Penrose and Stuart Hameroff have speculated that consciousness is the result of quantum gravity effects in microtubules, which they dubbed Orch-OR (orchestrated objective reduction). But Max Tegmark, in a paper in Physical Review E, calculated that the time scale of neuron firing and excitations in microtubules is slower than the decoherence time by a factor of at least 10,000,000,000. The reception of the paper is summed up by this statement in his support: "Physicists outside the fray, such as IBM's John A. Smolin, say the calculations confirm what they had suspected all along. 'We're not working with a brain that's near absolute zero. It's reasonably unlikely that the brain evolved quantum behavior', he says." The Tegmark paper has been widely cited by critics of the Penrose-Hameroff proposal. It has been claimed by Hameroff to be based on a number of incorrect assumptions (see linked paper below from Hameroff, Hagan and Tuszyński), but Tegmark in turn has argued that the critique is invalid (see rejoinder link below). In particular, Hameroff points out the peculiarity that Tegmark's formula for the decoherence time includes a factor of T2 in the numerator, meaning that higher temperatures would lead to longer decoherence times. Tegmark's rejoinder keeps the factor of T2 for the decoherence time.

Religious views

Penrose has stated that he does not hold to any religious doctrine.[11] However, in the film A Brief History of Time he stated: "There is a certain sense in which I would say the universe has a purpose. It's not there just somehow by chance. Some people take the view that the universe is simply there and it runs along–it's a bit as though it just sort of computes, and we happen by accident to find ourselves in this thing. I don't think that's a very fruitful or helpful way of looking at the universe, I think that there is something much deeper about it, about its existence, which we have very little inkling of at the moment."[12]

Awards and honours

Roger Penrose during a lecture, explaining the tessellation in the MC Escher lithograph Circle Limit IV

Penrose has been awarded many prizes for his contributions to science. He was elected a Fellow of the Royal Society of London in 1972. In 1975, Stephen Hawking and Penrose were jointly awarded the Eddington Medal of the Royal Astronomical Society. In 1985, he was awarded the Royal Society Royal Medal. Along with Stephen Hawking, he was awarded the prestigious Wolf Foundation Prize for Physics in 1988. In 1989 he was awarded the Dirac Medal and Prize of the British Institute of Physics. In 1990 Penrose was awarded the Albert Einstein Medal for outstanding work related to the work of Albert Einstein by the Albert Einstein Society. In 1991, he was awarded the Naylor Prize of the London Mathematical Society. From 1992 to 1995 he served as President of the International Society on General Relativity and Gravitation. In 1994, Penrose was knighted for services to science.[13] In 1998, he was elected Foreign Associate of the United States National Academy of Sciences. In 2000 he was appointed to the Order of Merit. In 2004 he was awarded the De Morgan Medal for his wide and original contributions to mathematical physics. To quote the citation from the London Mathematical Society:

His deep work on General Relativity has been a major factor in our understanding of black holes. His development of Twistor Theory has produced a beautiful and productive approach to the classical equations of mathematical physics. His tilings of the plane underlie the newly discovered quasi-crystals.

In 2005 Penrose was awarded an honorary doctorate (Honoris Causa) by Warsaw University and Katholieke Universiteit Leuven (Belgium), and in 2006 by the University of York. In 2008 Penrose was awarded the Copley Medal. He is also a Distinguished Supporter of the British Humanist Association and one of the patrons of the Oxford University Scientific Society.

Works

Penrose also wrote forewords to Quantum Aspects of Life and Zee's book Fearful Symmetry.

See also

Notes

  1. ^ The Atheism of the Gaps
  2. ^ Belief in God in an Age of Science by John Polkinghorne
  3. ^ Atheists top book charts by deconstructing God | UK news | The Observer
  4. ^ Penrose, R (2005), The Road to Reality: A Complete guide to the Laws of the Universe, Vintage Books, ISBN 0-099-44068-7 
  5. ^ Penrose and his father shared mathematical concepts with Dutch graphic artist M. C. Escher which were incorporated into a number of pieces, including Waterfall, which is based on the 'Penrose triangle', and Up and Down.
  6. ^ J. C. Raven's 1936 MSc thesis features introspections from Penrose, aged four and two thirds, as he solved what are now known as Raven's Progressive Matrices, c.f. note 52 of Watt, D. C. (1998). Lionel Penrose, F.R.S. (1898-1972) and Eugenics: Part One. Notes and Records of the Royal Society of London, 52, 137-151
  7. ^ R. Penrose (1979). "Singularities and Time-Asymmetry". in S. W. Hawking and W. Israel. General Relativity: An Einstein Centenary Survey. Cambridge University Press. pp. 581–638. 
  8. ^ Jaromír Korčák (1938): Deux types fondamentaux de distribution statistique. Prague, Comité d’organisation, Bull. de l'Institute Int'l de Statistique, vol. 3, pp. 295–299.
  9. ^ "If an Electron Can Be in Two Places at once, Why Can't You?". http://discovermagazine.com/2005/jun/cover/article_view?b_start:int=0&-C=. Retrieved 2008-10-27. 
  10. ^ "Dr. Roger Penrose at Penn State University". http://www.phys.psu.edu/people/display/index.html?person_id=233&mode=contact.. Retrieved 2007-07-09. 
  11. ^ http://www.samharris.org/site/book_letter_to_christian_nation/
  12. ^ http://www.godresources.org/intelligent_design5.shtml
  13. ^ Official announcement knighthood. The London Gazette. 11 June 1994.

References

  • Ferguson, Kitty (1991). Stephen Hawking: Quest For A Theory of Everything. Franklin Watts. ISBN 0-553-29895-X.
  • Misner, Charles; Thorne, Kip S. & Wheeler, John Archibald (1973). Gravitation. San Francisco: W. H. Freeman. ISBN 0-7167-0344-0. ; see Box 34.2.

External links


 
 
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tessellation
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