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Gravity's Engines

With 'Gravity's Engines,' Caleb Scharf establishes himself as one of the finest space storytellers.

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Gravity’s Engines
Caleb Scharf
Farrar, Straus and Giroux
239 pp.

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In free market economics, the theory of “creative destruction” is considered a necessary linchpin in understanding how capitalism works. No matter how nostalgically attached we may be to certain fixtures in our world, change is inevitable and ongoing. In order for the new to emerge, the old must give way – sometimes its reign overthrown through jarring, unpleasant acts of usurpation.

So, too, with what scientists hypothesize about the universe. One day, they speculate, even Planet Earth may be swept away by forces that are utterly indifferent to our own existential desire for longevity and having the same home in perpetuity.

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It could involve a strike by asteroid, though among all known agents of cosmic creative destruction, none are more potently menacing – and intriguing – than black holes, the subject of Caleb Scharf’s Gravity’s Engines: How Bubble-Blowing Black Holes Rule Galaxies, Stars, and Life In The Cosmos.

“Among all the conceptions of the human mind, we have really outdone ourselves with these objects – they are fantastical, dreamlike, and mythological in stature,” Scharf writes. “But they are much more than just a tall tale – they are a vital and active part of all that we see around us.”

Scharf, who is director of the astrobiology department at Columbia University, is gifted in his written musings on celestial phenomena which have appeared in Scientific American magazine and other venues. His primary passion is joining colleagues from around the world in the search ofr solar systems, much like our own, that may harbor planets with life. With technological innovation – i.e., stronger telescopes – the odds of eventually finding one appear to be good.

In "Gravity’s Engines," Scharf hits the bull’s eye in his analysis of the latest ponderings on black holes, the arcane understanding of which has risen to public awareness largely through Hollywood science fiction films and most notably franchises like "Star Trek."

Repeating the observations of Galileo, Scharf notes that Earth, of course, is not at the center of the universe; it’s not even at the center of our galaxy. What does reside in the heart of the Milky Way, unbeknownst to scientists until only recently, is a “supermassive black hole” – a “dark star” that, like a worrisome whirlpool, sucks in the matter around it and yet, at the same time, throws off profound amounts of energy.

Astrophysicists estimate that it may be four million times the mass of our own sun and joins uncountable numbers of other black holes set in the dark maws of space.

The projection of radiation and elemental particles from the lips of black holes, called “event horizons,” seems to have affected not only the way that galaxies are constructed but where individual stars, among billions and billions, settle into place, Scharf notes. More minutely, but of great relevance to us, it also appears that black holes affect how gravity holds planets and moons in delicate orbits.

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The paradox of black holes is that although being pulled into one would spell certain doom, they likely are responsible for the convergence of forces that gave Earth its miraculous positioning as a star-circling orb conducive to life as we know it.

Fundamentally, what exactly is a black hole? As Scharf explains, it’s the ultimate expression of gravity. Black holes are not “things” so much as  “regions of spacetime” comprised of ultra-dense matter in which super-gravitational forces prevent everything, including light, from escaping. The more that a black hole consumes, the theory goes, the bigger it becomes.

While black holes are conceptual outgrowths of Albert Einstein’s theory of relatively, even Einstein had his doubts about whether black holes would actually exist. Scharf is among a bold generation of 21st-century physicists, versed in quantum mechanics, that have confirmed them from afar.

Black holes are believed to be created when stars burn themselves out and collapse unto themselves due to hyper-gravity, squishing their mass into super compactness. Their density then pulls in other objects around it, capable even of bending time as it inescapably dips over the event horizon.

Fortunately, it could be billions of years before our own sun, likely to produce merely a smallish black hole, falls into itself like a demolished building. But what about the big mama black hole that is continuously growing in the middle of the Milky Way?

In Scharf’s hands, it is heart-thumping to ponder. “Although we are relatively sheltered, a modest wash of radiation [projected by that black hole] out here on the galactic rim every few hundred thousands years could temporarily modify the atmospheric chemistry of a small rock planet,” Scharf says.

“Even small changes can have big consequences. A little more or less ozone, a little more or less watery precipitation, and the fortunes of a particular organism could take a turn for the better or worse.”

Is Scharf worried? Hardly, not any more than he is about the eventual collision of the Milky Way and its neighboring galaxy, Andromeda, in a few billion years.

"Gravity’s Engine," for the lay reader who gazes into the heavens, is enjoyable and eminently accessible because of the way Scharf translates concepts of astrophysics using easy-to-grasp metaphors.

The great value of "Gravity’s Engines" is that it pulls together most of the known black hole science. According to Scharf, there may be “hundreds of billions, perhaps trillions, of black holes scattered throughout the universe.”

With "Gravity’s Engines," Scharf, a Briton by birth, establishes his credentials as a fine cosmic storyteller, sharing company with a line of popular writers that extends from giant big thinker Stephen Hawking and the late Carl Sagan to noted physicist Brian Greene. What’s gut-wrenching is that for all that Scharf and his colleagues are able to discern, he admits they know very little, the least of which is why. What's tantalizing is that new insights, produced by a constellation of international colleagues, are being divined on a regular basis. 

Todd Wilkinson is a Monitor contributor.