An Introduction To Modern Cosmology Second Edition

Author: Andrew Liddle

Published in: John Wiley & Sons

ISBN: 0-470-84835-9

File Type: pdf

File Size:  12 MB

Language: English


The development of cosmology will no doubt be seen as one of the scientific triumphs of the twentieth century. At its beginning, cosmology hardly existed as a scientific discipline. By its end, the Hot Big Bang cosmology stood secure as the accepted description of the Universe as a whole. Telescopes such as the Hubble Space Telescope are capable of seeing light from galaxies so distant that the light has been travelling towards us for most of the lifetime of the Universe. The cosmic microwave background, a fossil relic of a time when the Universe was both denser and hotter, is routinely detected and its properties examined. That our Universe is presently expanding is established without doubt. We are presently in an era where understanding of cosmology is shifting from the qualitative to the quantitative, as rapidly-improving observational technology drives our knowledge forward. The turn of the millennium saw the establishment of what has come to be known as the Standard Cosmological Model, representing an almost universal consensus amongst cosmologists as to the best description of our Universe. Nevertheless, it is a model with a major surprise — the belief that our Universe is presently experiencing accelerated expansion. Add to that ongoing mysteries such as the properties of the so-called dark matter, which is believed to be the dominant form of matter in the Universe, and it is clear that we have some way to go before we can say that a full picture of the physics of the Universe is in our grasp.

Such a bold endeavour as cosmology easily captures the imagination, and over recent years there has been increasing demand for cosmology to be taught at university in an accessible manner. Traditionally, cosmology was taught, as it was to me, as the tail end of a general relativity course, with a derivation of the metric for an expanding Universe and a few solutions. Such a course fails to capture the flavour of modern cosmology, which takes classic physical sciences like thermodynamics, atomic physics and gravitation and applies them on a grand scale. In fact, introductory modern cosmology can be tackled in a different way, by avoiding general relativity altogether. By a lucky chance, and a subtle bit of cheating, the correct equations describing an expanding Universe can be obtained from Newtonian gravity.

From this basis, one can study all the triumphs of the Hot Big Bang cosmology — the expansion of the Universe, the prediction of its age, the existence of the cosmic microwave background, and the abundances of light elements such as helium and deuterium — and even go on to discuss more speculative ideas such as the inflationary cosmology. The origin of this book, first published in 1998, is a short lecture course at the University of Sussex, around 20 lectures, taught to students in the final year of a bachelor's degree or the penultimate year of a master's degree. The prerequisites are all very standard physics, and the emphasis is aimed at physical intuition rather than mathematical rigour. Since the book's publication cosmology has moved on apace, and I have also become aware of the need for a somewhat more extensive range of material, hence this second edition. To summarize the differences from the first edition, there is more stuff than before, and the stuff that was already there is now less out-of-date.

Cosmology is an interesting course to teach, as it is not like most of the other subjects taught in undergraduate physics courses. There is no perceived wisdom, built up over a century or more, which provides an unquestionable foundation, as in thermodynamics, electromagnetism, and even quantum mechanics and general relativity. Within our broadbrush picture the details often remain rather blurred, changing as we learn more about the Universe in which we live. Opportunities crop up during the course to discuss new results which impact on cosmologists' views of the Universe, and for the lecturer to impose their own prejudices on the interpretation of the ever-changing observational situation. Unless I've changed jobs (in which case I'm sure www. google. com will hunt me down), you can follow my own current prejudices by checking out this book's WWW Home Page at There you can find some updates on observations, and also a list of any errors in the book that I am aware of. If you are confident you've found one yourself, and it's not on the list. I'd be very pleased to hear of it. The structure of the book is a central 'spine', the main chapters from one to fifteen,  which provide a self-contained introduction to modern cosmology more or less reproducing the coverage of my Sussex course. In addition there are five Advanced Topic chapters, each with prerequisites, which can be added to extend the course as desired. Ordinarily the best time to tackle those Advanced Topics is immediately after their prerequisites have been attained, though they could also be included at any later stage. I'm extremely grateful to the reviewers of the original draft manuscript, namely Steve Eales, Coel Hellier and Linda Smith, for numerous detailed comments which led to the first edition being much better than it would have otherwise been.

Thanks also to those who sent me useful comments on the first edition, in particular Paddy Leahy and Michael Rowan-Robinson, and of course to all the Wiley staff who contributed. Matthew Colless.  Brian Schmidt and Michael Turner provided three of the figures, and Martin Hendry, Martin Kunz and Franz Schunck helped with three others, while two figures were generated from NASA's SkyView facility (http: / /skyview. gsfc.nasa. gov) located at the NASA Goddard Space Flight Center. A library of images, including full-colour versions of several images reproduced here in black and white to keep production costs down, can be found via the book's Home Page as given above.
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