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14 of 14 people found the following review helpful:
5.0 out of 5 stars
Outside the Box, June 9, 2008
This review is from: The Wraparound Universe (Hardcover)
This book on Cosmology is in a class by itself, so the reader who is already familiar with the "Standard Model" should expect some surprises. The central theme is the following : instead of a simple topology, the Universe could have a multiply connected topology, and could be much smaller than is usually assumed. Therefore, in this "dodecahedral" Universe, some of the galaxies we see are not real galaxies, but are only images of other galaxies! The author, Jean-Pierre Luminet, apart from being an astrophysicist and a specialist on black holes, is also a gifted writer, who has published many scientific novels and even some poetry, in addition to many popular books on astrophysics and cosmology(unfortunately, most of them are in French.For more information, the interested reader may want to visit his webpage at luth2.obspm.fr). So he leads the reader to this conclusion in a step-by-step fashion, and he explains all the nooks and crannies of cosmology, without forgetting the Einstein field equations and the Friedmann equations, which are the basis for all cosmological models. Then, drawing on his own research in cosmic topology, which is too technical to be part of this book, he uses the latest estimates of the cosmological parameters, especially the total density Omega(slightly larger than 1) to conclude that the Universe must have a multiply connected topology. This is in contradiction with the "mainstream" inflationary paradigm, which uses the same data to prove that the Universe is spatially flat, and therefore infinite. Hence a dispute between "cosmologists" and "topologists", which the latter think they would eventually win, because their theory gives a natural explanation of the so-called "low multipole anomaly" in the power spectrum of the CMB. Luminet, with whom I had some correspondence about this and some other of his books, hopes that the Planck satellite, expected to be launched in October 2008, would give a much more accurate CMB power spectrum than WMAP, which will eventually resolve this tantalizing issue. But whatever the outcome, this beautiful book, which offers an example of thinking "outside the box", is a must read for all those interested in Cosmology, and I highly recommend it.
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13 of 13 people found the following review helpful:
5.0 out of 5 stars
Modern cosmology and sociology of science, July 12, 2008
This review is from: The Wraparound Universe (Hardcover)
I would like to add further comments to the first review by G. Melki. The first and simplest is about the book structure, a collection of 45 very short chapters that make easier for the reader to follow her/his natural "pace". I think that the attention to the reader's needs is one of the reasons why Luminet's books (originally writtenin French) have been translate into other languages. Second, an important part of the book is about sociology of science. Comments about the impact of different ideas or even about the same ideas in different historic and geographic conditions are scattered through all the book, and are especially concentrated at the end. Just to limit this review to modern aspects, I could say that inflation is favored by many scientists, even though it is not without problems. Naively, one can realize that inflation forbids observation of multiply connected topologies, just because one expects that the radius of the universe has been inflated so much that it lies well beyond the cosmic horizon. However, Luminet stresses that this is not enough to discard such nontrivial topologies a priori, and that one should interpret the experimental observations also from different points of view. Other subtleties are also reviewed. For example, chapter 39 is all about the problem of measuring the curvature of the universe. Despite few recent claims that the space is Euclidean, which implies that the density parameter is _exactly_ 1, the author emphasizes that we can never measure any value with certainty, so that it is impossible to state that "space is flat". Instead, modern measurements are compatible with this hypothesis but favor values of the density parameter that are a bit larger than one, so that it seems that the geometry is spherical. Because all spherical topologies are closed spaces, this is a suggestion that the universe is spatially closed, even though the usual preferred model is that of a infinite Euclidean space! Finally, Luminet shows that the most recent data about the cosmic background radiation from the WMAP satellite are better fit by "well-proportioned spaces", among which the best one seems to be the _spherical dodecahedral Poincaré space_, whose volume is 120 times smaller than the hypersphere (i.e. the simply connected topology) with the same curvature. This conclusion has been criticized by many researchers, but cannot be falsified with the present data, so that we need to wait until data from the PLANCK satellite will be available.
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8 of 8 people found the following review helpful:
5.0 out of 5 stars
Unique topic that has not been explored in any cosmology book I know., November 11, 2008
This review is from: The Wraparound Universe (Hardcover)
I fully agree with earlier reviews. It is a beautiful and important book that will expand any cosmology follower's knowledge. I have never encountered a cosmic topology subject in numerous publications dealing with Universe (please see my Listmania). I had no idea of topology role in establishing whether global shape of space is finite or infinite. Briefly: we learn, that for spherical finite space general relativity shows how to indirectly measure the curvature of the space. Its value depends on the average density of matter/energy that it contains. However for the geometries of the two other families, Euclidean and hyperbolic, the finite or infinite character of space no longer depends simply on the curvature and on the energy density: it depends on the TOPOLOGY ! While for decades observational cosmology pushed itself to determine the curvature parameters directly while neglecting the topological possibilities, it could be that in the XXI century, it would be primarily the experimental determination of the topology of the Universe that would allow us to fix, with great precision, the curvature and the cosmological constant - those traditional parameters on which the ultimate fate of the cosmos depends: perpetual expansion or eventual contraction. Is theory of Big Bang truly valid and confirmed? - author presents its limits and simplifications. However I must admit that some parts of the book are not easy, as reader is asked to jump from two to three dimensions. This require stretching imagination to the limit (chapters about multiply connected spaces leading to cosmic crystallography methods). Lack of glossary of terms is detrimental, particularly, because there are many of them here, not to be found in other cosmology books. Nevertheless it is fascinating lecture - do not miss it !
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