A World Without Time: The Forgotton Legacy Of Godel And Einstein [Anglais] [Relié]

What if time is only an illusion, if it doesn't actually exist? Yourgrau, a Brandeis professor of philosophy, explains that Einstein's general theory of relativity may allow for this possibility, first realized by the great logician Kurt Gödel. Gödel is best known for his incompleteness theorem, one of the most important theorems in mathematical logic since Euclid. In a typically brief paper written for a Festschrift to honor his friend and Princeton neighbor Einstein, Gödel theorized the existence of what have come to be called Gödel universes: rotating universes in which time travel is possible. But if one can travel through time, how can time as we know it exist in these other universes, since the past is always present? And if time doesn't exist in other universes, then it may not exist in ours either. Yourgrau (The Disappearance of Time) writes that Gödel's paper was almost universally ignored, and he claims that since the logician's death, philosophers have gone out of their way to try to denigrate his work in fields other than logic. This book will appeal to fans of Douglas Hofstadter's Gödel, Escher, Bach and to Einstein junkies, and makes a fascinating companion to Rebecca Goldstein's Incompleteness (Forecasts, Dec. 20), but all readers who enjoy a good thought experiment or having basic preconceptions about their world challenged will enjoy this. (Jan.)
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*Starred Review* During the half-dozen years before his death, Einstein's best friend was the Austrian logician Kurt Godel. Famous for his incompleteness theorems demonstrating that formal mathematical systems could not fully describe reality, Godel was spurred by Einstein's theories of relativity to discover that, in any universe fully described by those theories, time doesn't exist. He did this by proving the possibility of time travel, the catch being that if a past point in time can be reached, then it cannot have passed, which contradicts intuitive understanding of time. Einstein died before he could respond to Godel's revelation. Since then, except for troopers such as Yourgrau (this is his third and most popularly pitched book on Godel), philosophers have ignored the implications of time not existing in physical reality, which are that time must be an ideal and that philosophically long-discounted Platonism, which asserts the reality of the ideal, needs reconsideration. Such studied ignorance springs, Yourgrau says, from philosophers' disdain for Godel as a mere logician. He was also powerfully, pathetically eccentric--different from but not unlike Einstein in that respect--and Yourgrau relieves and arguably also informs demanding passages on Godel's work by sketching his life and personality as well as his thought. Ray Olson
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It is a widely known but insufficiently appreciated fact that Albert Einstein and Kurt Goedel were best friends for the last decade and a half of Einstein's life. They walked home together from Princeton's Institute for Advanced Study every day; they shared ideas about physics, philosophy, politics, and the lost world of German-Austrian science in which they had grown up. What is not widely known is that in 1949 Goedel made a remarkable discovery: there exist possible worlds described by the theory of relativity in which time, as we ordinarily understand it, does not exist. He added a philosophical argument that demonstrates, by Goedel's lights, that as a consequence, time does not exist in our world either. If Goedel is right, Einstein has not just explained time; he has explained it away.

Without committing himself to Goedel's philosophical interpretation of his discovery, Einstein acknowledged that his friend had made an important contribution to the theory of relativity, a contribution that he admitted raised new and disturbing questions about what remains of time in his own theory. Physicists since Einstein have tried without success to find an error in Goedel's physics or a missing element in relativity itself that would rule out the applicability of Goedel's results. Philosophers, for the most part, have been silent.

_A World Without Time_, addressed to experts and non experts alike, brings to life the sheer intellectual drama of the companionship of Goedel and Einstein, and places their discoveries -- which can only be measured on a millennial scale -- in the context of the great and disturbing intellectual movements of the twentieth century -- in physics, mathematics, logic, philosophy, and the arts. It contains, as well, a poignant and intimate account of the friendship between these two thinkers, each put on the shelf by the scientific fashions of their day -- and ours -- and attempts to rescue from undeserved obscurity the work Goedel did, inspired by Einstein, which made clear for the first time the truly revolutionary nature of the theory of relativity, which to this day is hardly recognized.

Palle Yourgrau is Associate Professor of Philosophy at Brandeis University. His 1999 monograph, _Goedel Meets Einstein: Time Travel in the Goedel Universe_, the only book length workon the philosophical significance of Goedel's cosmological ideas, sparked a resurgence of interest among philosophers in Goedel's ideas about time and relativity. He lives in Cambridge, Massachusetts.