Review by Booklist Review
Gravity is so strong in a black hole that nothing, including light, can escape. There is evidence that supermassive black holes, like Sagittarius A* in the Milky Way, exist at the center of all galaxies. White holes, on the other hand, are hypothetical and have never been observed. Theory suggests that unlike black holes, light, energy, and information can only escape from white holes. Nothing can enter them. Some even speculate that the Big Bang itself was the result of a white hole singularity. Here theoretical physicist Rovelli (Helgoland, 2021) draws on his theories of loop quantum gravity, quantum mechanics, and time to unravel the origin of white holes and to consider the tightly bound relationship between black holes and white holes. Rovelli writes for non-physicists, so that anyone interested in cosmology, whether they have a science background or not, will appreciate his clear, straightforward style. Scientists now understand that 95 percent of the universe is "missing," leading to questions surrounding dark matter and dark energy. Are white holes part of the answer?
From Booklist, Copyright (c) American Library Association. Used with permission.
Review by Publisher's Weekly Review
This mind-bending outing by physicist Rovelli (Anaximander) explores the possibility of the existence of white holes, the hypothesized inverse of black holes. He explains that black holes were first proposed as a consequence of Einstein's equations on general relativity, but because the equations "do not specify a direction for time," it's possible to run them with "the sign of the time variable flipped," meaning that there may a point at which a black hole "rebounds and retraces its previous route in time, like a basketball bouncing." After a black hole passes such a point, it becomes a white hole. If humans were able to survive inside a black hole, Rovelli suggests, they could reach the bottom and then "cross through and emerge into a white hole where time is reversed," spending no more than a few seconds inside but emerging billions of years later due to the dilation of time. Rovelli does a solid job of making the underlying science accessible, even if some of the finer points may go over general readers' heads, such as his explanation of why "you can only enter a black hole, and you can only exit a white hole." Still, those with a background in physics will be sucked in. Photos. (Oct.)
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Review by Kirkus Book Review
The bestselling author and theoretical physicist looks at "the elusive younger siblings of black holes." Since white holes may be an inevitable consequence of black holes, Rovelli, the author of Seven Brief Lessons in Physics and Reality Is Not What It Seems, begins with an explanation, noting that white holes are essentially the reverse of a black hole. Since the 18th century, scientists knew that, as a universal force, gravity from an extremely massive star should slow its light's speed to zero. That concept made little sense until Einstein showed that light never slows but that gravity distorts space, so light near a massive body appears to curve. The more massive the body, the greater the curve until the light doubles back. Einstein insisted that no such body existed, but his equations permit it, and they eventually turned up. All stars eventually run out of fuel and collapse. Average stars like our sun end up as tiny, immensely dense dwarfs. The largest stars, however, continue to collapse, ultimately to an infinitely tiny, infinitely dense point. Their light doubles back, resulting in a black hole, from which nothing that enters can leave. Even time stops dead at its edge, or "event horizon." Mathematics, Einstein's included, doesn't work when dimensions are infinitely small or large, so physicists don't know what happens when a black hole forms. That hasn't stopped them from speculating, and Rovelli leads one school favoring the production of white holes, a bizarre concept that is still purely theoretical. Calling on quantum mechanics, which deals with minuscule phenomena, he explains that the collapsing star never becomes infinitely small but "bounces," leading to a white hole. There, matter can leave but never enter; "a white hole is a black hole with time reversed." Rovelli works hard, sometimes successfully, to explain matters, but he is dealing with phenomena so complex that he often gives readers permission to skip ahead. Heavy-duty popular science not for the faint of heart. Copyright (c) Kirkus Reviews, used with permission.
Copyright (c) Kirkus Reviews, used with permission.
