November 15, 2020
An update on the early years of the cosmos. In her first nonfiction book, Chapman reviews the history, including new discoveries which have overturned accepted theories on the evolution of the universe, but she reserves most of her excitement for the "dark ages"--from 380,000 to roughly 1 billion years after the Big Bang. The early universe was a superheated soup of subatomic particles and energy. After nearly 400,000 years, the temperature had dropped enough to allow electrically neutral atoms to form and photons to travel freely. There was light and gas but nothing else. As it expanded and cooled, its matter--almost all hydrogen and helium--drifted about. Eventually, some clouds drifted together, and gravity began to pull. The clouds shrank and grew hotter, and a collapsing cloud grew so hot--millions of degrees--that its hydrogen became helium in a process known as fusion, which produces titanic amounts of energy. These were the first stars, born perhaps 180 million years after the Big Bang. Mostly brighter, hotter, bigger, and shorter-lived than today's, they ended their lives and blew up, which produced "metals" (in astrophysics, elements other than hydrogen and helium) and scattered them, a process that formed other stars and eventually planets and humans. Do any primordial, metal-free stars still exist? The big ones are long gone, but small, sunlike stars have extremely long lifetimes. Evidence for their existence is turning up in obscure regions, such as dwarf galaxies and the outskirts of the Milky Way. Detecting them requires massive observatories, high-tech spectrographs, and the soon-to-be-launched $10 billion James Webb space telescope. Clearly fascinated by her subject, Chapman works diligently to describe the early universe, gradually introducing information about the life cycles of stars and techniques astrophysicists use to search for them. Her careful step-by-step explanations delve far deeper than a NOVA documentary, so readers must pay attention, but most will find it worth the effort. Good astrophysics for committed readers.
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December 7, 2020
Astrophysicist Chapman debuts with a spirited history of the early universe when stars “roared to life.” Her focus is on the period “from 380,000 years after the Big Bang to about 1 billion years after it,” known as the dark ages because of how little is known about it. Chapman begins by explaining light and the electromagnetic spectrum, and from there, surveys the first stars in the universe, Population III stars. The standard hypothesis, she explains, is that the stars were formed by gravity, combustion, and nuclear fusion acting upon clouds of gas. Chapman brings things up to the present with an outline of the ways astronomers are searching for data in the stars with huge arrays of terrestrial radio telescopes, the Hubble Space Telescope, and the upcoming James Webb Space Telescope. Chapman’s tone is conversational, and she has a knack for breaking down complex scientific material (the dark ages’ “missing cosmological data is equivalent to missing everything from the moment of conception to the first day of school”), though she can go on distracting tangents (as with a digression on King Tut’s tomb as a lead-in to “stellar archaeology”). Nonetheless, those looking for an introduction to stellar evolution will find much here to dig into.
December 1, 2020
Astrophysicists trying to decipher the beginning of our universe are hampered by some missing data. Specifically, they'd like to know what happened during the first billion years or so after the Big Bang, when the first generation of stars was created. This book is British astrophysicist Chapman's overview of evolving theories about these Population III non-metallic stars, in light of current research (some as recent as early 2020). The text can get pretty technical at times, but Chapman employs a conversational tone and sprinkles in stories and wry observations that will keep readers entertained. While clearly excited about recent developments, especially rapidly proliferating deep-space antennae fields sweeping far-flung galaxies for clues, Chapman acknowledges that cosmologists are often guided by assumptions versus known facts (the title of the final chapter is ""Unknown Unknowns""). Readers will happily follow along as Chapman covers centuries of speculation, unexplained anomalies, informed conjectures, and current reasoned suppositions. Her enthusiasm is contagious, and should strike just the right notes with audiences who enjoy pondering the mysteries of the universe.
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