An Introduction to Cosmology

Rating:
Summary: Schizophrenic Textbook
Review: (My review is based on the second edition of this textbook.)

This is, in many ways a solid introduction to standard cosmology, with a more thorough than usual discussion of alternatives to the standard cosmologies. While the explanation of such topics as the Jeans equation in an expanding universe, is reasonably good, the book is somehow schizophrenic in nature. I will give an example.

In Chapter 11, the author gives as an example of problems with the standard cosmology the fact that redshifts are apparently periodic (Fig. 11.6). The author also shows in Chapter 7 how dark matter simulations produce cellular structures in the universe (Figs 7.5a and b). Well, he does not make the obvious connection between cellular structure and periodicity of distances (implying also periodicity of redshifts). This is an incredible oversight on the part of the author, making this book NOT a recommended introduction to cosmology.

Rating:
Summary: Be prepared to think...
Review: Jayant Narlikar's 'Introduction to Cosmology' has a simple enough title, but do not be deceived. This is a graduate-level textbook on one of the most difficult subjects around--mathematical, theoretical explorations of large-scale universal structures.

If, as Stephen Hawking once said, for every equation in the book, you lose half your readership, I would calculate (just off the top of my head) that only a dozen people have read this book! Actually, to be serious, this book presupposes a knowledge of calculus (differential equations, vector analysis, Fourier series, etc.) and assumes a fairly extensive knowledge of physics (thermodynamics, electromagnetic theory, atomic structure, fluid dynamics).

This is intended as a text book for the advanced undergraduate or graduate level student, and to that end, it has problems, most of which are computational in nature.

'It is usual to find cosmology appearing at the end of a text on general relativity, introduced more as an appendage than as a subject in its own right. Perhaps this is one reason why cosmology still stands apart from the rest of astronomy, where it really belongs. The astronomer tends to regard cosmology as a playground for general relativists rather than a logical extension of extragalactic astronomy.'

Narlikar introduces general relativistic theory as a tool rather than a subject, for use in understanding the geometrical principles applied to cosmology. He continues forward to use standard models (Friedmann) of cosmology as solutions to Einstein's equations, before progressing to discussing the physical properties of cosmology, including galactic evolution (structure, kinematics and dynamics--one could refer here then to Milhaus and Binney's work on the same), particle physics and early universe issues.

From here, Narlikar progresses to some non-standard cosmological constructions, including anisotropic cosmologies, steady state theories and cosmologies that might correspond to the Mach principle (although, as the name non-standard would indicate, these are fringe, or sometimes, older theories, which are largely discredited, but science must look to them as they occasionally give insight into observations). This, as an introduction, is not exhaustive, and does not get into cosmological models such as Alfven & Klein's matter-antimatter symmetry, the Einstein-Cartan cosmologies, or Milne's kinematic relativity, or the ideas of Segal or McCrea.

From here Narlikar ends the book with discussion of observational cosmology, exploring the implications of local observations (such as background microwave radiation that permeates the universe, a discovery of Penzias and Wilson at Bell Telephone Laboratories), the Hubble Constant and redshift issues, and quasars (do they or do they not fit standard models of cosmology and scientific principles currently known?).

'By claiming to describe the universe as a whole, cosmology transcends the realms of all other branches of science. Any conclusions about the universe are bound to be profound and hence must be drawn with caution. This caution is often missing in statements about cosmology. All too often the investigator (whether a theoretician or an observer) is tempted to mistake the model of the universe for the real thing. Categorical remarks about the state of the universe are often found upon closer examination to be model-dependent. Firm claims about observations of the universe have had to be withdrawn later when a better assessment of the observational error became possible.'

In conclusion, Narlikar gives an brief summary of the cases for and against standard cosmological models, and a glimpse into future research, which will be aided as observational tools become more sensitive.

This is a science text book, and thus is rather dry and straightforward in presentation. But as a tool for the high-end astronomer/astrophysicist, it is a valuable work.

Rating:
Summary: Be prepared to think...
Review: Jayant Narlikar's `Introduction to Cosmology' has a simple enough title, but do not be deceived. This is a graduate-level textbook on one of the most difficult subjects around--mathematical, theoretical explorations of large-scale universal structures.

If, as Stephen Hawking once said, for every equation in the book, you lose half your readership, I would calculate (just off the top of my head) that only a dozen people have read this book! Actually, to be serious, this book presupposes a knowledge of calculus (differential equations, vector analysis, Fourier series, etc.) and assumes a fairly extensive knowledge of physics (thermodynamics, electromagnetic theory, atomic structure, fluid dynamics).

This is intended as a text book for the advanced undergraduate or graduate level student, and to that end, it has problems, most of which are computational in nature.

`It is usual to find cosmology appearing at the end of a text on general relativity, introduced more as an appendage than as a subject in its own right. Perhaps this is one reason why cosmology still stands apart from the rest of astronomy, where it really belongs. The astronomer tends to regard cosmology as a playground for general relativists rather than a logical extension of extragalactic astronomy.'

Narlikar introduces general relativistic theory as a tool rather than a subject, for use in understanding the geometrical principles applied to cosmology. He continues forward to use standard models (Friedmann) of cosmology as solutions to Einstein's equations, before progressing to discussing the physical properties of cosmology, including galactic evolution (structure, kinematics and dynamics--one could refer here then to Milhaus and Binney's work on the same), particle physics and early universe issues.

From here, Narlikar progresses to some non-standard cosmological constructions, including anisotropic cosmologies, steady state theories and cosmologies that might correspond to the Mach principle (although, as the name non-standard would indicate, these are fringe, or sometimes, older theories, which are largely discredited, but science must look to them as they occasionally give insight into observations). This, as an introduction, is not exhaustive, and does not get into cosmological models such as Alfven & Klein's matter-antimatter symmetry, the Einstein-Cartan cosmologies, or Milne's kinematic relativity, or the ideas of Segal or McCrea.

From here Narlikar ends the book with discussion of observational cosmology, exploring the implications of local observations (such as background microwave radiation that permeates the universe, a discovery of Penzias and Wilson at Bell Telephone Laboratories), the Hubble Constant and redshift issues, and quasars (do they or do they not fit standard models of cosmology and scientific principles currently known?).

`By claiming to describe the universe as a whole, cosmology transcends the realms of all other branches of science. Any conclusions about the universe are bound to be profound and hence must be drawn with caution. This caution is often missing in statements about cosmology. All too often the investigator (whether a theoretician or an observer) is tempted to mistake the model of the universe for the real thing. Categorical remarks about the state of the universe are often found upon closer examination to be model-dependent. Firm claims about observations of the universe have had to be withdrawn later when a better assessment of the observational error became possible.'

In conclusion, Narlikar gives an brief summary of the cases for and against standard cosmological models, and a glimpse into future research, which will be aided as observational tools become more sensitive.

This is a science text book, and thus is rather dry and straightforward in presentation. But as a tool for the high-end astronomer/astrophysicist, it is a valuable work.