Review: At the Edge of Time



At the Edge of Time: Exploring the Mysteries of Our Universe’s First Seconds
by Dan Hooper
Princeton Univ. Press, 2019
hardcover, 248 pp., illus.
ISBN 978-0-691-18356-5
US$24.95

In a speech near the end of last month’s International Astronautical Congress in Washington, NASA administrator Jim Bridenstine talked about the science that can be done in and around the Moon, including science not directly related to the Moon itself. One example he mentioned is a proposed mission called the Dark Ages Polarimetry Pathfinder (DAPPER) that would use the radio-quiet region on the Moon’s far side to enable observations of the distant, early universe. “We’re going to see not just the first light in the universe after the Big Bang, we’re going to see before the first light,” he said. “We’re going to see what are called the ‘dark ages.’’”

That dark age early in the history of the universe is also a mystery for cosmologists. From a few hundred thousand years after the Big Bang to the present, the wealth of data available “leaves us confident that we understand this portion of our universe’s history quite well,” Dan Hooper writes in the first chapter of his new book, At the Edge of Time. That certainty decreases closer to the Big Bang, to the point of being “little more than an informed guess” about what happened in the first few seconds after the Big Bang. Yet, understanding that era is critical to understanding our universe today and its future.

Hooper, a senior scientist at Fermilab and professor at the University of Chicago, takes the reader on a tour of our collective ignorance about the early universe in his book. Understanding the earliest moments of the universe is vital to deciphering mysteries like dark matter and dark energy, as he describes in the book, including his own work on the subject: he found a signature in gamma-ray observations of the galactic center by NASA’s Fermi spacecraft consistent with one model of dark matter that could provide insights into the early universe.

There’s also the matter of matter itself—or, rather, why there’s any matter at all. “According to the math, the world should be virtually free of atoms,” he writes, since it should have been annihilated with equal amounts of antimatter. The early universe “must have been host to significant transformative events—events that we still know almost nothing about. We know this is true because if it weren’t, we would not exist.”

While many science books emphasize what we do know about the universe, the focus on Hooper’s book is on what we do not know about the early universe, despite ongoing efforts ranging from spacecraft to particle accelerators to shed light on those dark ages. He doesn’t hesitate to discuss the failures of those efforts, like a lack of detections of dark matter or high-energy subatomic particles predicted by some models.

“If you are looking for a story with an ending that wraps up nicely, you may have chosen the wrong book,” Hooper writes in the introduction. But science is a messy endeavor, with a dead ends and false alarms and backtracking; that can still be an interesting story, and this book succeeds in explaining both what we do know about the universe’s origins and what remains unknown.

Some of those mysteries may never be revealed, he suggests, because there is no way to collect the data needed: “there may one day be an end to the great line of human inquiry that we call the science of cosmology.” But scientists like Hooper aren’t giving up soon, with DAPPER just one of many efforts to help to make those dark ages a little less dark.


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