Friday, April 26, 2019

Book Review: "The Cosmic Cocktail"

If you were to leave the book The Cosmic Cocktail on your coffee table, any guests would likely think it pertained to bartending. However, this book by University of Michigan professor Katherine Freese, actually details the quest to learn what material comprises dark matter.

Freese's preferred candidate for dark matter is the Weakly Interacting Massive Particle or WIMP. Writes Freese: "A major reason that WIMPs are taken so seriously as dark matter candidates is a feature known as the WIMP miracle. Because these particles undergo only weak interactions (in addition to feeling gravity), they miraculously turn out to have the right abundance today to solve the dark matter problem" (p. 104).

Freese reviews several projects that have tried to detect WIMPS, discussing evidence consistent and inconsistent with their appearance. As of 2014 (the book's publication year), Freese's conclusion was that, "Despite the uncertainties, theorists have become tremendously excited by all the recent hints of detection and are trying to reconcile the apparent discrepancies among the data" (p. 181). However, a December 2018 update from Sophia Chen in Wired magazine reports that only the DAMA experiment in Italy (discussed extensively by Freese) has produced "compelling evidence" of dark-matter WIMPS. Chen conveys, further, that some researchers are developing "WIMP fatigue."

Whereas facilities such as the Large Hadron Collider, which are built to produce new particles from proton collisions, get a lot of attention, there are other ways to approach the problem. Freese discusses, among other methods, how "dark matter particles from the Galaxy might interact with atomic nuclei in direct detection experiments located in underground laboratories beneath mountains or in abandoned mines" (p. 124). The process of getting an underground facility going can take 15 years or so (summarized on pp. 141-142).

Finally, Freese mixes in a healthy dose of personal stories, describing colorful and illustrious physicists (some of whom she studied under or worked with), graduate-school experiences, projects she's worked on, and conferences she's attended. Included in the latter is her (and other physicists') favorite spot for margaritas by the coast in Los Angeles! I would recommend the book for anyone with a particular interest in dark matter.