Cosmology 1st Edition

Here I am in the year 2018. Cosmology, the monograph authored by Steven Weinberg, is the last book on the topic I purchased and studied. That purchase was made 2008. Between then and now (between 2008 and 2018) we have witnessed a plethora of speculation, the multiverse being one example. I confess, such speculation (multiverse and others) had turned me off to the topic. I revel in comparison of experimental numbers to theoretical predictions. Thus, my affinity for two classics of Cosmology: Physical Cosmology (James Peebles) and Cosmology (Steven Weinberg). Why is that so ? Numbers from experiment weighed against theoretical predictions are the leitmotif of the two books. Steven Weinberg has written another winning exposition.(1) Weinberg begins with "distance indicators." Read: "the agreement between the values of Hubble Constant provided by these very different methods will serve to validate the cosmological assumptions made in the analysis of cosmic microwave background." (page 31). Before "turning to dynamical theory" we are reminded of the variety of different measures of distance (page 33). Dynamical theory alerts the reader to the importance of General Relativity for the subject. Read: "Lorentz invariance requires that in locally inertial coordinate systems the energy-momentum tensor of the vacuum must be proportional to the Minkowski metric." (page 40). This is your first view of Vacuum Energy.(2) We remain in chapter one: Expansion of the Universe. Quintessence..."a time-varying vacuum energy" (page 89). Nearly ten pages of exposition where "it may be illuminating to work out the consequences of this one specific model of quintessence." Excellent Pedagogy !(3) Second Chapter--Cosmic Microwave Radiation Background. This is first brush with the topic, it recurs, time and time again. Grab one of those Modern Physics textbooks and brush-up on "blackbody radiation." (Richtmyer and Kennard). Return to Steven Weinberg for more specialized applications--anisotropies and fluctuations--these will be analyzed. Fourier integrals, Legendre polynomials, Gaussian distributions, all of that and more will be utilized. Conclude with a comparison between experiment and theory.(4) Before reading chapter three--Early Universe--study Weinberg's 1977 book, The First Three Minutes. Then, return. Now, avail yourself of the fine exposition regards "Cold Dark Matter" (page 185). Read: "if the particles that make up most of the mass of the Universe are not Baryons, what are they ? "Wimps, Supersymmetry and Axions, these things--and more--will occupy the next fifteen pages...as prelude to....(5) Inflation. Read: "the details of inflation are unknown...it has had one significant experimental success, a prediction of some of the properties of the fluctuations in the cosmic microwave background and large-scale structure." (page 202). Learn of Flatness ("least convincing argument for inflation"), Horizons ("inflation provides an explanation") and Monopoles.(6) Revisit fluctuations. General relativity (field equations) is front-and-center. Revisit Fourier analysis and "Whatever happens during Inflation, if the Universe subsequently spends sufficient time in a state of local thermal equilibrium with no non-zero conserved quantities, then the perturbations become adiabatic--and, they remain adiabatic subsequently--even when the conditions of thermal equilibrium are no longer satisfied." That statement says a lot ! The ensuing chapter six will provide more details of cosmological fluctuations. Before study of chapter six, a refresher of hydrodynamic, kinetic and Boltzmann equations proves useful.(7) Next, a tough chapter seven. The chapter revisits the anisotropies in the cosmic background radiation. Read: "The general agreement of theory and observation, both for microwave background anisotropies alone and for background anisotropies in conjunction with other observations, goes far to confirm the general assumptions of the cosmological model, including cold dark matter and dark energy, that we have been using." (page 362). A nice thirty-page exposition on polarization concludes the chapter: "polarization due to scattering by free electrons" which may become more important "in revealing the effects of gravitational waves produced during inflation." (pages 370-400).(8) Read from chapter nine, Gravitational Lenses: "For cosmology, the most promising application of gravitational lenses probably lies in surveys of weak lensing, the study of distortion of distant galaxies by numerous small deflections of light as it passes from galaxies to us through a slightly inhomogeneous distribution of matter.(9) The final chapter ten revisits fluctuations. Or, more accurately, inflation as the origin of cosmological fluctuations. Read: "Why should the action of gravitation contain only the Einstein term, and not other generally covariant terms with more than two derivatives of the metric ? And, why should the action of the standard electroweak model or quantum chromodynamics contain only renormalizable terms ? " Learn about it in these pages.(10) There are appendices: one is survey of general relativity (eighteen pages) and Newtonian cosmology. Another (appendix H) outlines material needed for understanding of Boltzmann equation (as prelude to chapter six and seven). The Cosmology text of Weinberg was my latest serious look into cosmology.No matter what the future holds, because Weinberg presents experimental numbers alongside theoretical models, his book remains invaluable. Without such interplay between experiment and theory, I am hard-pressed to call the subject physics.

As a graduate in experimental nuclear physics (MSc, also now a retiree of 65), I read Prof. Weinberg's The First Three Minutes, and Dreams of a Final Theory, when I was actively working in the field of nuclear engineering. I bought the author's three volume books on the QED, and, of course, this book too, because of his mathematically rigorous descriptions of theoretical models of Nature. Because I have also read Prof. Andrei Linde's "Particle Physics and Inflationary Cosmology," I have wondered if Prof. Weinberg also writes something about "Consciousness," but no mention of it, maybe simply because "Consciousness" cannot be put on a mathematically rigorous basis as yet. What I have confirmed from this book is Prof. Weinberg is, apparently, mathematically rigorous a Materialist.We know that there are many Dualists in the field of parapsychology, John Beloff, for example. I can understand these Dualists' position; they cannot deny the existence of Non-physical Realm as well as Physical Realm, both based on their convincing facts. But from my point of view, these Dualists are dualists because they cannot deny the existence of at least One Objective Physical Realm, i.e. our Universe. How can we, conscious Egos, (not the Unconscious) deny it! Maybe, our Universe was created as explained in this book, or as in Genesis, for example. However, we also have "Psychical Knowledge" given by the non-physical entity "Seth" through the trance-channeling of the late American writer-poet Jane Roberts (1929-1984); the knowledge tells us, the conscious Egos, that "Consciousness" is the origin of everything!

This book is a dense treatise on cosmology targeted for graduate students and professional physicists. But the clarity of Weinberg's prose and math makes this a valuable reference for anyone seriously interested in cosmology. If you grasp 5% of the material here you will have learned more than is contained in any of the popularized treatments.Weinberg wastes no time, beginning with a one page derivation of the FLRW metric, relating it to the Hubble constant, and following up with a presentation and critical analysis of experimental results from Hubble to the Type 1A supernova project. Nothing is "beyond the scope" of this book, and Weinberg gives a thorough treatment of critical elements no matter how difficult -- e.g. detailed calculation of the CMB fluctuations.

VERY GOOD!!!!