The Cosmic Century: A History of Astrophysics and Cosmology , MalcolmLongair , Cambridge U. Press, New York, 2006. $65.00 (545 pp.). ISBN 978-0-521-47436-8

Recent advances in physics and astronomy have brought about in our knowledge of the universe a revolution comparable to the one that occurred at the end of the 16th century and through the 17th century during the times of Tycho Brahe, Johannes Kepler, Galileo, and Isaac Newton. Since the first part of the 20th century, we have been able to answer some of the questions that humankind has always asked: How old is the universe, and how did it start? What makes stars evolve, shine, and die? And how do galaxies, planets, and elements form?

However, in the past 50 years the rate of astronomical discoveries has increased rapidly, thanks to powerful new observatories on the ground and in space. The entire range of wavelengths emitted by celestial objects, from radio waves to gamma rays, can now be observed. The data can be analyzed, stored, and distributed by powerful computers. So, what have we found? Perhaps the most striking result is that the universe appears to be filled predominantly with forms of energy and matter different from the normal baryonic matter of everyday objects. What determines the dynamics and the evolution of the universe is subject to natural laws that researchers do not yet fully comprehend. Once again astronomy is posing some of the most fundamental questions for physics.

In The Cosmic Century: A History of Astrophysics and Cosmology , Malcolm Longair has written a very timely book, directed toward students, researchers, and lecturers; I enjoyed experiencing all three roles while reading it. It is a lucid and in-depth presentation of the subject and introduces topics at various levels of complexity. The Cosmic Century is different from most books on astrophysics and cosmology that are either for the general public or for a specialized audience. The author covers the historical advances in the field with regard to their impact on the astrophysical worldview. In its 16 chapters describing observations and theory, the book takes us through the logical developments and the interactions between data and interpretation. At an even deeper level are the notes and appendixes to the chapters, in which Longair treats specific subjects in greater detail, often with the appropriate mathematics.

Longair is, in my opinion, uniquely qualified to write this tour de force. As a professor of natural philosophy and head of the Cavendish Laboratory at the University of Cambridge, he has conducted significant research in high-energy astrophysics, astrophysical cosmology, and the history of physics. He is a brilliant lecturer and prolific writer. Among his books are Theoretical Concepts in Physics: An Alternative View of Theoretical Reasoning in Physics for Final-Year Undergraduates (Cambridge U. Press, 1984) and Galaxy Formation (Springer, 1998). He has contributed to some of the major astronomical projects on the ground and in space, including the Hubble Space Telescope . His service on many of the committees involved in setting priorities for astronomical research has given him a wonderful insight into how modern astronomy is done and what it may offer as future advances.

Parts 1 and 2 of the book give a very useful account of the progress from astronomy to astrophysics in the last part of the 19th century by introducing the advances in spectroscopy and in the classification of stellar spectra. He summarizes the development of theories of stellar structure and evolution in a manner particularly useful for many physicists who have joined that subfield.

After describing the theoretical and observational advances of the early 20th century, the author introduces readers to modern astronomy in part 3. In this section he narrates with great authority the opening up of the entire electromagnetic spectrum to astronomical observations and the impact of that achievement on the theory of stellar evolution. In addition, Longair covers the physics of the interstellar medium and cluster and galaxy evolution, a subject close to his own research.

The last portion of the book, parts 4 and 5, describes the advances of astrophysical cosmology over the past 50 years—from our knowledge of the origin of the universe, including the development of structure and its evolution, to our measurement of cosmological parameters.

Longair’s style very effectively engages the reader in the story of this wonderful adventure of the human mind. I think The Cosmic Century would be of great value to anybody who has some technical background, is interested in the subject, and wants a fascinating introduction to the field. I would particularly recommend it to researchers for its scholarly historical presentation and to students for its effectiveness as a great learning aid.