ONCE BEFORE TIME

The latest effort to make sense of the universe by a young physicist.

In his debut, Bojowald (Physics/Pennsylvania State Univ.) points out that general relativity and quantum mechanics, the two magnificent explanations of physical phenomena, don’t explain everything. For example, solving their equations to describe earlier periods of the universe works beautifully until everything reaches an infinitely small point, the Big Bang singularity, where the temperature of the universe is infinite. Infinities are a no-no in science; their appearance doesn’t necessarily invalidate a theory but reveals that it needs work. The crucial problem is that quantum mechanics describes matter in the universe but says nothing about gravity or space/time, which is the domain of relativity. Bojowald describes 50 years of effort to meld the two into “quantum gravity,” which would clear up major difficulties in cosmology, including what happened during the Big Bang—or whether it happened at all. A consummate researcher, the author works hard to explain his preferred solution, “loop quantum gravity,” with a nod toward the leading rival, string theory. Along the way he delivers updates on current thinking on black holes, dark matter and energy and the fate of the universe, along with digressions into myths, literature and philosophy. Like Brian Greene in The Elegant Universe (2003), Bojowald simplifies a complex subject as much as possible but no further. Those who remember high-school physics or who enjoyed Stephen Hawking’s A Brief History of Time (1988) will have a more satisfying experience.

Cutting-edge physics made accessible for readers who pay close attention.