The Clockwork Universe: Isaac Newton, the Royal Society, and the Birth of the Modern World - Edward Dolnick (2011)
Part I. Chaos
Chapter 15. A Play Without an Audience
The new science inspired ridicule and hostility partly for the simple reason that it was new. But the resentment had a deeper source—the new thinkers proposed replacing a time-honored, understandable, commonsense picture of the world with one that contradicted the plainest facts of everyday life. What could be less disputable than that we live on a fixed and solid Earth? But here came a new theory that beganby flinging the Earth out into space and sending it hurtling, undetectably, through the cosmos. If the world is careening through space like a rock shot from a catapult, why don’t we feel it? Why don’t we fall off?
The goal of the new scientists—to find ironclad, mathematical laws that described the physical world in all its changing aspects—had not been part of the traditional scientific mission. The Greeks and their successors had confined their quest for perfect order to the heavens. On Earth, nothing so harmonious could be expected. When the Greeks looked to the sky, they saw the sun, the moon, and the planets moving imperturbably on their eternal rounds.20 The planets traced complicated paths (planet is Greek for “wanderer”), but they continued on their way, endlessly. On the corrupt Earth, on the other hand, all motions were short-lived. Drop a ball and it bounces, then rolls, then stops. Throw a rock and seconds later it falls to the ground. Then it sits there.
Ordinary objects could certainly be set moving—an archer tensed his muscles, drew his bow, and shot an arrow; a horse strained against its harness and pulled a plow—but here on Earth an inanimate body on its own would not keep moving. The archer or the horse evidently imparted a force of some kind, but whatever that force was it soon dissipated, as heat dissipates from a poker pulled from a fire.
Greek physics, then, began by dividing its subject matter into two distinct pieces. In the cosmos above, motion represents the natural state of things and goes on forever. On the Earth below, rest is natural and motion calls for an explanation. No one saw this as a problem, any more than anyone saw a problem in different nations following different laws. Heaven and Earth completely differ from one another. The stars are gleaming dots of light moving across the sky, the Earth a colossal rock solid and immobile at the center of the universe. The heavens are predictable, the Earth anything but. On June 1, to pick a date at random, we know what the stars in the night sky will look like, and we know that they will look virtually the same again on June 1 next year, and next century, and next millennium.21 What June 1 will bring on Earth this year, or any year, no one knows.
Aristotle had explained how it all works, both in the heavens and on Earth, about three hundred years before the birth of Christ. For nearly two thousand years everyone found his scheme satisfactory. All earthly objects were formed from earth, air, fire, and water. The heavens were composed of a fifth element or essence, the quintessence, a pure, eternal substance, and it was only in that perfect, heavenly domain that mathematical law prevailed. Why do everyday, earthly objects move? Because everything has a home where it belongs and where it returns at the first opportunity. Rocks and other heavy objects belong down on the ground, flames up in the air, and so on. A “violent” motion—flinging a javelin into the air—might temporarily overcome a “natural” one—the javelin’s impulse to fall to the ground—but matters quickly sort themselves out.
The picture made sense of countless everyday observations: Hold a candle upright or turn it downward, and the flame rises regardless. Hoist a rock overhead in one hand and a pebble in the other, and the rock is harder to hold aloft. Why? Because it is bigger and therefore more earth-y, more eager to return to its natural home.
All such explanations smacked of biology, and to modern ears the classical world sounds strangely permeated with will and desire. Why do falling objects accelerate? “The falling body moved more jubilantly every moment because it found itself nearer home,” writes one historian of science, as if a rock were a horse returning to the barn at the end of the day.
The new scientists would strip away all talk of “purpose.” In the new way of thinking, rocks don’t want to go anywhere; they just fall. The universe has no goals. But even today, though we have had centuries to adapt to the new ideas, the old views still exert a hold. We cannot help attributing goals and purposes to lifeless nature, and we endlessly anthropomorphize. “Nature abhors a vacuum,” we say, and “water seeks its own level.” On a cold morning we talk about the car starting “reluctantly” and then “dying,” and if it just won’t start we pound the dashboard in frustration and mutter, “Don’t do this to me.”
It was Galileo more than any other single figure who finally did away with Aristotle. Galileo’s great coup was to show that for once the Greeks had been too cautious. Not only were the heavens built according to a mathematical plan, but so was the ordinary, earthly realm. The path of an arrow shot from a bow could be predicted as accurately as the timing of an eclipse of the sun.
This was a twofold revolution. First, the kingdom of mathematics suddenly claimed a vast new territory for itself. Second, all those parts of the world that could not be described mathematically were pushed aside as not quite worthy of study. Galileo made sure that no one missed the news. Nature is “a book written in mathematical characters,” he insisted, and anything that could not be framed in the language of equations was “nothing but a name.”22
Aristotle had discussed motion, too, but not in a mathematical way. Motion referred not only to change in position, which can easily be reduced to number, but to every sort of change—a ship sailing, a piece of iron rusting, a man growing old, a fallen tree decaying. Motion, Aristotle decreed in his Physics, was “the actuality of a potentiality.” Galileo sneered. Far from investigating the heart of nature, Aristotle had simply been playing word games, and obscure ones at that.
In the new view, which Galileo hurried to proclaim, the scientist’s task was to describe the world objectively, as it really is, not subjectively, as it appears to be. What was objective—tangible, countable, measurable—was real and primary. What was subjective—the tastes and textures of the world—was dubious and secondary. “If the ears, the tongue, and the nostrils were taken away,” wrote Galileo, “the figures, the numbers, and the motions would indeed remain, but not the odors nor the tastes nor the sounds.”
This was an enormous change. Peel away the world of appearances, said Galileo, and you find the real world beneath. The world consists exclusively of particles in motion, pool balls colliding on a vast table. All the complexity around us rises out of that simplicity.
After Galileo and Newton, the historian of science Charles C. Gillispie has written, science would “communicate in the language of mathematics, the measure of quantity,” a language “in which no terms exist for good or bad, kind or cruel . . . or will and purpose and hope.” The word force, for example, Gillispie noted, “would no longer mean ‘personal power’ but ‘mass-times-acceleration.’ ”
That austere, geometric world has a beauty of its own, Galileo and all his intellectual descendants maintained. The problem is that most people cannot grasp it. Mathematicians believe fervently that their work is as elegant, subtle, and rich as any work of music. But everyone can appreciate music, even if they lack the slightest knowledge of how to read a musical score. For outsiders to mathematics—which is to say, for almost everyone—advanced mathematics is a symphony played out in silence, and all they can do is look befuddled at a stage full of musicians sawing away to no apparent effect.
The headphones that would let everyone hear that music do exist, but they can only be built one pair at a time, by the person who intends to wear them, and the process takes years. Few people take the trouble. In the centuries that followed the scientific revolution, as the new worldview grew ever more dominant, poets would howl in outrage that scientists had stripped the landscape bare. “Do not all charms fly / At the mere touch of cold philosophy?” Keats demanded. Walt Whitman, and many others, would zero in even tighter. “When I heard the learn’d astronomer,” wrote Whitman, the talk of figures, charts, and diagrams made him “tired and sick.”
Mankind had long taken its place at the center of the cosmos for granted. The world was a play performed for our benefit. No longer. In the new picture, man is not the pinnacle of creation but an afterthought. The universe would carry on almost exactly the same without us. The planets trace out patterns in the sky, and those patterns would be identical whether or not humans had ever taken notice of them. Mankind’s role in the cosmic drama is that of a fly buzzing around a stately grandfather clock.
The shift in thinking was seismic, and the way it came about had nothing in common with the textbook picture of progress in science. Change came not from finding new answers to old questions but from abandoning the old questions, unanswered, in favor of new, more fruitful ones. Aristotle had asked why. Why do rocks fall? Why do flames rise? Galileo asked how. How do rocks fall—faster and faster forever, or just until they reach cruising speed? How fast are they traveling when they hit the ground?
Aristotle’s why explained the world, Galileo’s how described it. The new scientists began, that is, by dismissing the very question that all their predecessors had taken as fundamental. (Modern-day physicists often strike the same impatient tone. When someone asked Richard Feynman to help him make sense of the world as quantum mechanics imagines it, he supposedly snapped, “Shut up and calculate.”)
Aristotle had an excellent answer to the question why do rocks fall when you drop them? Galileo proposed not a different answer or a better one, but no answer at all. People do not “know a thing until they have grasped the ‘why’ of it,” Aristotle insisted, but Galileo would have none of it. To ask why things happen, he declared, was “not a necessary part of the investigation.”
And that change was only the beginning.