Roger Penrose
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Contents 
Career
In 1967, Penrose invented twistor theory which maps geometric objects in Minkowski space into the 4dimensional 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 black holes) by hiding them from our view.
Roger Penrose is wellknown for his 1974 discovery of Penrose tilings, which are formed from two tiles that can only tile the plane aperiodically. In 1984, similar patterns were found in the arrangement of atoms in quasicrystals. His most important contribution may be 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).
He has written controversial books such as The Emperor's New Mind (1989) in which he argues that known laws of physics do not constitute a complete system and that human consciousness cannot be explained until a new physical theory (what he terms correct quantum gravity, CQG) has been devised. He argues against the strong AI viewpoint that the processes of the human mind are algorithmic and can thus be duplicated by a sufficiently complex computer. This is based on claims that human consciousness transcends formal logic systems because things such as the insolvability of the halting problem and Gödel's incompleteness theorem restrict an algorithmically based logic from traits such as mathematical insight. These claims were originally made by the philosopher John Lucas of Merton College, Oxford.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 explaining 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. Further, AI programs can also conclude that false statements are true, so error is not unique to humans. Another dissenter, Charles Seife, has said, "Penrose, the Oxford mathematician famous for his work on tiling the plane with various shapes, is one of a handful of scientists who believe that the ephemeral nature of consciousness suggests a quantum process."
Penrose and Stuart Hameroff have constructed a theory in which human consciousness is the result of quantum gravity effects in microtubules. 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 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 PenroseHameroff proposal. However, it has since been claimed by Hameroff to be based on a number of incorrect assumptions. See the refutation linked below from Hameroff, Hagan and Tuczynksi.
In 2004 Penrose released The Road to Reality: A Complete Guide to the Laws of the Universe, a 1,099page book aimed at giving a comprehensive guide to the laws of physics. In the same year 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 (http://www.lms.ac.uk/activities/prizes_com/citations04.html)
 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 quasicrystals.
Books
 Roger Penrose, Techniques of Differential Topology in Relativity, Society for Industrial & Applied Mathematics, 1972, ISBN 0898710057 (rare)
 Roger Penrose and Wolfgang Rindler, Spinors and SpaceTime: Volume 1, TwoSpinor Calculus and Relativistic Fields, Cambridge University Press, 1987 (reprint), ISBN 0521337070 (paperback)
 Roger Penrose and Wolfgang Rindler, Spinors and SpaceTime: Volume 2, Spinor and Twistor Methods in SpaceTime Geometry, Cambridge University Press, 1988 (reprint), ISBN 0521347866 (paperback)
 Roger Penrose, The Emperor's New Mind: Concerning Computers, Minds, and The Laws of Physics, Oxford University Press, 1989, ISBN 0140145346 (paperback)
 Roger Penrose, Shadows of the Mind: A Search for the Missing Science of Consciousness, Oxford University Press, 1994, ISBN 0198539789 (hardback)
 Stephen Hawking and Roger Penrose, The Nature of Space and Time, Princeton University Press, 1996, ISBN 0691037914 (hardback), ISBN 0691050848 (paperback)
 Roger Penrose, The Large, the Small, and the Human Mind, (with Abner Shimony, Nancy Cartwright, and Stephen Hawking), Cambridge University Press, 1997, ISBN 0521563305 (hardback), ISBN 0521655382 (paperback), Canto edition: ISBN 0521785723
 Roger Penrose, The Road to Reality: A Complete Guide to the Laws of the Universe, Alfred Knopf, 2005, ISBN 0679454438
See also
External links
 Instructions for making the Penrose tiles (http://www.cs.uidaho.edu/~casey931/puzzle/penrose/penrose.html)
 Two theories for the formation of quasicrystals resembling Penrose tilings (http://www.sciencenews.org/sn_arch/10_12_96/bob1.htm)
 Tegmark, Max. 2000. "The importance of quantum decoherence in brain processes (http://www.arxiv.org/abs/quantph/9907009)". Physical Review E. vol 61. pp. 41944206.
 Hagan, Hameroff, Tuczynski: The debate on decoherence  "Biological feasibility of quantum states in the brain (http://www.quantumconsciousness.org/pdfs/decoherence.pdf)"
 Toilet Paper Plagiarism (http://www.parascope.com/articles/slips/fs_151.htm)
 Links to lectures and interviews with Roger Penrose (http://www.321books.co.uk/reviews/theroadtorealitybyrogerpenrose.htm)de:Roger Penrose
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