The Little Book of Cosmology
by Lyman Page
Princeton Univ. Press, 2020
hardcover, 152 pp., illus.
Physics and associated subjects, like cosmology, have plenty of canonical, and massive, books. Many physics students are acquainted with Gravitation, a classic textbook about general relativity whose authors include Nobel laurate Kip Thorne. Weighing in at more than 1,000 pages, the book seems massive enough to warp spacetime on its own.
By contrast, The Little Book of Cosmology is just that: a modest monograph whose main section (excluding an appendix) is only a little more than 100 pages, small enough to be easily misplaced. Despite its small size, though, the book offers a broad overview of our understanding of the origin and nature of the universe, and also what we don’t yet understand about it.
The author, Lyman Page, is a Princeton University professor and is described by the book jacket as “one of the world’s leading experimental cosmologists.” That job title makes it sound like he runs a lab where postdocs and grad students create and destroy universes. Instead, he studies the cosmic microwave background, and was one of the original co-investigators for NASA’s Wilkinson Microwave Anisotropy Probe (WMAP), a mission that produced one of the best maps yet of that signature of the Big Bang. (To be fair, “experimental cosmologist” sounds more interesting than, say, “astrophysicist”.)
It’s no surprise, then, that he examines cosmology through the prism of the cosmic microwave background, or CMB. After an introductory chapter about the size and age of the universe, Page turns to the CMB itself, a thermal afterglow from about 400,000 years after the Big Bang.
Studying the CMB in detail, including the structure of the faint fluctuations in it, can yield major insights into cosmology. That includes a “power spectrum” chart that plots the magnitude of those fluctuations as a function of their angular size on the sky; Page calls it “one of the most important plots in cosmology” because “we can determine the composition of the universe from the positions and amplitudes of the peaks.” He goes on to explain how analysis of that chart shows the relative contributions of matter, dark matter, and the cosmological constant (aka dark energy), among other parameters.
Page writes for an audience with some basic physics knowledge (an appendix includes some background information, like an overview of the electromagnetic spectrum, for those who need a refresher), but avoids equations or advanced math. The book moves quickly, though, so sometimes you may need to go back and reread a passage to understand how, say the power spectrum leads to measurements of the polarization of the CMB. Overall, the book provides a good high-level overview of our current knowledge of cosmology, without warping spacetime or a bookshelf.