The Clockwork Universe (9 page)

Chapter Fifteen
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
began
by 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 them
selves 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.

Chapter Sixteen
All in Pieces

Galileo, Newton, and their fellow revolutionaries immediately
turned their backs on yet another cherished idea. This time they banished common sense. Long acquaintance with the world had
always been hailed as the surest safeguard against delusion. The new scientists rejected it as a trap. “It is not only the heavens that are not as they seem to be, and not only motion,” Descartes argued, in a modern historian's paraphrase. “The whole universe is not as it seems to be. We see about us a world of qualities and of life. They are all mere appearances.”

It was a Polish cleric and astronomer named Nicolaus Copernicus who had struck the first and hardest blow against common
sense. Despite the evidence, plain to every child, that we live on solid ground and that the sun travels around us, Copernicus argued that everyone has it all wrong. The Earth travels around the sun, and it spins like a top as it travels. And no one feels a thing.

This was ludicrous, as everyone who heard about the newfangled theory delighted in pointing out. For one thing, the notion of a sun-centered universe contradicted scripture. Had not Joshua ordered the sun (rather than the Earth) to stand still
in the sky? This was a huge hurdle. In the 1630s, nearly a century
after Copernicus's death, Galileo would face the threat of torture and then die under house arrest for arguing in favor of a sun-centered universe.

(Isaac Newton was born in the year that Galileo died. That was coincidence, but in hindsight it seemed to presage England's rise to scientific preeminence and Italy's long drift to mediocrity.
What was not coincidence was that seventeenth-century England
welcomed science, on the grounds that science supported religion, and thrived; and seventeenth-century Italy feared science, on the grounds that science undermined religion, and decayed.)

Copernicus himself had hesitated for decades before pub
lishing his only scientific work,
On the Revolutions of the Celestial Spheres
, perhaps because he knew it would stir religious fury as well as scientific opposition. Legend has it that he was handed the first copy of his masterpiece on his deathbed, on May 24, 1543, although by that point he may have been too weak to recognize it.

Religion aside, the scientific objections were enormous. If Copernicus was right, the Earth was speeding along a gigantic racetrack at tens of thousands of miles an hour, and none of the passengers suffered so much as a mussed hair. The fastest that
any
traveler had ever moved was roughly twenty miles an hour, on horseback.

These arguments came from the most esteemed scholars, not from yokels. They knew, on both scientific and philosophical grounds, that the Earth does not move. (Aristotle had argued that the Earth rests in place because it occupies its natural home, the center of the universe, just as an ordinary object on the ground stays in
its
place unless something comes along and dislodges it.) Scholars pointed to countless observations that all led to the same conclusion. We can be sure the Earth stands still, one eminent philosopher explained, “for at the slightest jar of the Earth, we would see cities and fortresses, towns and mountains thrown down.”

But we don't see cities toppled, the skeptics noted, nor do we see any other evidence that we live on a hurtling platform. If we're racing along, why can we pour a drink into a glass without worrying that the glass will have moved hundreds of yards out of range by the time the drink reaches it? If we climb to the roof and drop a coin, why does it land directly below where we let it go and not miles away?

But Copernicus's new doctrine inspired fear as well as ridicule and confusion, because it led almost at once to questions that transcended science. If the Earth was only one planet among many, were those other worlds inhabited, too? By what sort of creatures? Had Christ died for
their
sins? Did they have their own Adam and Eve, and what did that say about evil and original sin? “Worst of all,” in the words of the historian of science Thomas Kuhn, “if the universe is infinite, as many of the later Copernicans thought, where can God's Throne be located? In an infinite universe, how is man to find God or God man?”

Copernicus could not disarm such fears by pointing to new discoveries or new observations. He never looked through a telescope—Galileo would be one of the first to turn telescopes to the heavens, some seven decades after Copernicus's death—and in any case telescopes could not
show
the Earth moving but only provided evidence that let one deduce its motion.

On the contrary, everything that Copernicus could see and feel spoke in favor of the old theories and against his own. “Sense pleads for Ptolemy,” said Henry More, a colleague of Newton at Cambridge and a distinguished English philosopher. But common sense lost out. The old, Earth-centered theory that Ptolemy had devised was a mathematical jumble, and that marked it for death. The old system worked perfectly well, but it was a hodgepodge.

The great challenge to pre-Copernican astronomy had to do with sorting out the motions of the planets, which do not trace a simple course through the sky but at some point interrupt their journey and loop back in the direction they've just come from. (The stars present no such mystery. Each night Greek astronomers watched them rotating smoothly through the sky, turning in a circle with the North Star at its center. Each constellation moved around the center, like a group of horses on a merry-go-round, but the stars within a constellation never rearranged themselves.)

The path of Saturn as seen from Earth, as depicted by Ptolemy in 132–33
A.D.
From March through June, Saturn appears to reverse course.

Accounting for the planets' strange course changes would
have been enough to give classical astronomers fits. Making the challenge all the harder, classical doctrine decreed that planets must travel in circular orbits (since planets are heavenly objects
and circles are the only perfect shape). But circular orbits didn't
fit the data. The solution was a complicated mathematical
dodge in which the planets traveled not in circles but in the next best thing—in circles attached to circles, like revolving seats on a Ferris wheel, or even in circles attached to circles attached to circles.

Copernicus tossed out the whole complicated system. The planets weren't really moving sometimes in one direction and sometimes in the other, he argued, but simply orbiting the sun. The reason those orbits look so complicated is that we're watching from the Earth, a moving platform that is itself circling the sun. When we pass other planets (or they pass us), it looks as if they've changed course. If we could look down on the solar
system from a vantage point above the sun, all the mystery would
vanish.

This new system was conceptually tidier than the old one, but it didn't yield new or better predictions. For any practical question—predicting the timing of eclipses and other happenings in the solar system—the old system was fully as accurate as the new. No wonder Copernicus kept his ideas to himself for so long. And yet think of the astonishing leap this wary thinker finally nerved himself to make. With no other rationale but replacing a cumbersome theory with one that was mathematically more elegant, he dared
to
set the Earth in motion
.

A few intellectuals might have been won over by a revolutionary argument with nothing in its favor but aesthetics. Most people wanted more. How did the new theory deal with the most basic questions? “If the moon, the planets and comets were of the same nature as bodies on earth,” wrote Arthur Koestler, “then they too must have ‘weight'; but what exactly does ‘the weight' of a planet mean, what does it press against or where does it tend to fall? And if the reason why a stone falls to Earth
is not the Earth's position in the center of the universe, then just
why does the stone fall?”

Copernicus did not have answers, nor did he have anything to
say about what keeps the planets in their orbits or what holds
the stars in place. The Greeks
had
provided such answers, and the
answers had stood for millennia. (Each planet occupied a spot on an immense, transparent sphere. The spheres were nested,
one inside the other, and centered on the Earth. The stars occupied the biggest, most distant sphere of all. As the spheres
turned, they carried the planets and the stars with them.)

No one could yet answer the new questions about the stars and planets. No one knew why objects on Earth obey one set of laws and bodies in the heavens another. No one even knew where to look for answers. John Donne, poet and cleric, spoke for many of his perplexed, frustrated contemporaries. “The Sun is lost, and th' earth, and no man's wit / Can well direct him where to look for it,” he lamented, in a poem written a year after Galileo first looked through his telescope.

“The new Philosophy calls all in doubt,” Donne wrote in another verse. “ 'Tis all in pieces, all coherence gone.”