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Janos Bolyai, Non-Euclidean Geometry, and the Nature of Space | 
 enlarge | Author: Jeremy J. Gray
Publisher: The MIT Press
Category: Book
List Price: $22.00
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Rating:  2 reviews
Sales Rank: 1136296
Media: Paperback
Pages: 256
Number Of Items: 1
Shipping Weight (lbs): 1
Dimensions (in): 8 x 5.1 x 0.9
ISBN: 0262571749
Dewey Decimal Number: 516.9
EAN: 9780262571746
Publication Date: June 1, 2004
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Condition: Brand new item. Over 4 million customers served. Order now. Selling online since 1995. Few left in stock - order soon. Code: M20081113105712T
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Product Description
Janos Bolyai (1802-1860) was a mathematician who changed our fundamental ideas about space. As a teenager he started to explore a set of nettlesome geometrical problems, including Euclid's parallel postulate, and in 1832 he published a brilliant twenty-four-page paper that eventually shook the foundations of the 2000-year-old tradition of Euclidean geometry. Bolyai's "Appendix" (published as just that?an appendix to a much longer mathematical work by his father) set up a series of mathematical proposals whose implications would blossom into the new field of non-Euclidean geometry, providing essential intellectual background for ideas as varied as the theory of relativity and the work of Marcel Duchamp. In this short book, Jeremy Gray explains Bolyai's ideas and the historical context in which they emerged, were debated, and were eventually recognized as a central achievement in the Western intellectual tradition. Intended for nonspecialists, the book includes facsimiles of Bolyai's original paper and the 1898 English translation by G. B. Halstead, both reproduced from copies in the Burndy Library at MIT.
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| Customer Reviews:
Readable history, difficult paper May 3, 2007
Viktor Blasjo
2 out of 2 found this review helpful
I find Bolyai's paper quite hopeless to read; it's a strange choice for semi-popular publication. Gray's introduction is very pleasant and interesting and full of historical background, but his commentary on Bolyai's actual paper is quite short and not always clear. He does comment extensively on Bolyai's squaring of the circle but this construction is too complicated to be very enjoyable. This result, and Bolyai's entire approach, depends on hyperbolic trigonometric formulae. He saw that such formulae should exist by finding a correspondence between a hyperbolic plane and a surface in hyperbolic space whose geometry is Euclidean (F-surface, horosphere). Today we may interpret this in terms of the half-space model. As our hyperbolic plane we can take a hemisphere centred at the origin and as the horosphere we can take a plane z=c. Lines on the hemisphere are of course intersections with planes perpendicular to the x-y-plane, and lines on the horosphere are Euclidean lines. Under vertical projection of one onto the other lines go to lines and angles are preserved. So a Euclidean right-angle triangle with one vertex at the z-axis correspond to a hyperbolic right-angle triangle with one vertex at the z-axis. And by rotating about the z-axis we see that the ratio of circumferences of the circles generated by the other two vertices is the same on both surfaces. This relates side lengths and thus gives a way of transferring Euclidean trigonometry to the hyperbolic plane. But in hyperbolic geometry the circumference does not grow linearly with the radius (but rather as the hyperbolic sine of the radius, as Bolyai shows later using the angle of parallelism formula), so Euclidean trigonometry does not transfer literally.
alternatives to Euclid December 31, 2004
W Boudville (Terra, Sol 3)
3 out of 8 found this review helpful
For some 2000 years, Euclid's postulates of geometry were considered the final word. As axioms, they seemed unassailable. Yet this neat little book describes how one mathematician stumbled on equally valid alternatives. Gray shows how Bolyai started by looking at Euclid's most controversial axiom. That two parallel lines in a plane will not intersect. An alternative formulation of which is that the angles of a triangle will always sum to pi radians.
Bolyai was able to show that by replacing this axiom, he could derive other self consistent geometric systems. One of which was inadvertantly already well known - the geometry of the surface of a sphere.
Gray goes on to show how this became the mathematical percursor to Einstein's theory of relativity, and our deeper understanding of space-time.
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