Top positive review
A stimulating, often moving exploration
Reviewed in the United States on August 11, 2019
Richard Panek is one of America's best science writers. Actually he's more than that. Instead of "discoveries," "breakthroughs," and other clichés that characterize much science writing, Panek is interested in the evolution of thought; in the men and women who have struggled — frequently at odds with one another — to understand puzzles that have persisted for up to thousands of years; and in the changing spirits of the times that often determine those thinkers' successes or failures. Because of Panek's broad perspective, The Trouble With Gravity is both powerful and unique.
The book's subtitle promises to solve a mystery, and in fact solves many. The one it can't solve is what gravity IS. Just three pages in we learn that physicists — beginning with Kip Thorne, Nobel Prize-winner (for his part in the detection of gravitational waves) and movie-maker (an executive producer of Interstellar and cocreator of its storyline) — think that "What is gravity?" is a meaningless question. On page seven Panek drops the other shoe: "I'll give away the ending of this book: I still won't know what gravity is."
People were trying to understand gravity long before it was named (after gravitas, Latin for weight) or accepted as having something to do with what Earth is made of. To humans it seems to be a strong force, which can hurt us badly if we slip and fall. Just such an incident in a library started Panek pondering this utterly common yet utterly mysterious phenomenon.
While the ancients' ideas were shrewd and subtle, they were often mistaken. Within the last two centuries we've realized that gravity is actually weak — indeed, more than a million billion billion billion times weaker than the familiar electromagnetic force. Panek uses one of my favorite illustrations to make the point: the entire mass of planet Earth is required to hold a paper clip down on a tabletop; a toy magnet lifts it easily.
In the mythic past it seemed obvious that we live in a divided universe, the "down here" and the "up there," the part we stand on and the part overhead. "Down here" is where weight drags us down; the worst of it is underneath us, called Tartarus or Hell or some equivalent thereof. The fun part is overhead, where we can watch the sun as it moves across the sky by day, or follow the moon and planets by night against a glittering backdrop of fixed stars. What, besides the gods, causes these varied motions?
Panek examines an early answer from the last chapter of Plato's Republic (ca 380 BCE). Plato creates the myth of a soldier named Er who returns from the dead, sent as a kind of messenger from the judges of the afterworld. He reports that the judges direct bad souls to the left and down and good ones to the right and up; the nature of "up," the heavens, is meticulously described as a mechanism involving a whirling spindle. Its internal details resemble Ptolemy's Earth-centered nested spheres (ca 150 CE) and Copernicus's sun-centered ones (1543 CE).
This remarkable forerunner of astronomical proposals that would still be in play two thousand years later is the kind of surprise Panek's book revels in. Wilder surprises abound in his treatment of Aristotle, Kepler, Galileo, Newton, Einstein, and others whom Panek calls "the usual suspects."
From myth to metaphysics to the unfolding of the scientific method itself, the theme throughout The Trouble With Gravity is its elusive nature. Although he had plenty of critics and shocked resisters, Newton defined his theory — which, not incidentally, erased the distinction between up there and down here — with such mathematical precision that it lasted without significant alteration for over 200 years. Still, Newton was distressed by it: "that one body may act upon another at a distance thro' a Vacuum . . . is to me so great an Absurdity that I believe no Man who has . . . a competent Faculty of thinking can ever fall into it." Nevertheless, he was forced to accept the absurdity: his own math was the proof.
It took Einstein to introduce a major amendment to Newton's theory. The fundamental thesis of General Relativity is that matter bends space and space guides matter. The result is a collection of previously unimaginable distortions of both time and space, including gravitational lenses, black holes, and the reluctant but unavoidable acceptance of multiple universes as a reasonable answer to why gravity is so weak: as Panek puts it, gravity may be "something that bleeds into our universe from an adjoining universe, or . . . an artifact from a colliding universe."
There's much more to The Trouble With Gravity, but I'll leave that in the readers' hands. What makes this book so compelling is its attention to the human struggle to extract meaning from an intricate universe. Panek's empathy for the searchers, from the most ancient philosophers and myth makers to today's brightest young theorists and experimentalists, is what makes the scientific quest come alive. He puts it well: "and so the ancient conversation continues."