The Clockwork Universe Page 25

  But early scientists found themselves bewildered even so. The problem was that the theory predicted, but it did not explain. Why do rocks fall? “Because of gravity,” the world has said ever since Newton, but that answer only pins a name to our ignorance. Molière long ago made fun of the doctor who explained that opium makes us sleepy because it has a “dormitive potency.” When Newton published the Principia, many scientists hailed his mathematics but denounced “gravity” as the same sort of empty explanation. They demanded to know what it meant to say that the sun pulled the planets. How did it pull them? What did the pulling?

  Another difficulty cut deeper. Today we’ve grown accustomed to thinking of modern science as absurd and unfathomable, with its talk of black holes and time travel and particles that are neither here nor there. “We are all agreed that your theory is crazy,” Niels Bohr, one of the twentieth century’s foremost physicists, once told a colleague. “The question that divides us is whether it is crazy enough to have a chance of being correct.” We think of classical science, in contrast, as a world of order and structure. But Newton’s universe was as much an affront to common sense as anything that modern science has devised, and Newton’s contemporaries found his theory crazy, too.

  One of the great mysteries of modern science is where consciousness comes from. How can a three-pound hunk of gray meat improvise a poem or spin out a dream? In Newton’s day, gravity was just as bewildering.52 How could it be that every hunk of matter pulls every other? Newton’s scheme seemed fantastically elaborate—the Alps pulled the Atlantic Ocean, which pulled back and pulled the Tower of London at the same time, which pulled Newton’s pen, which pulled the Great Wall of China. How could all those pulls also stretch to the farthest corners of space, and do so instantly? How does gravity snag a comet speeding outward past the farthest planets and yank it back toward us?

  Every aspect of the picture was mystifying. Gravity traveled across millions of miles of empty space? How? How could a force be transmitted with nothing to transmit it? Leibniz was only one of many eminent thinkers who hailed the brilliance of Newton’s mathematics but scoffed at his physics. “He claims that a body attracts another, at whatever distance it may be,” Leibniz jeered, “and that a grain of sand on earth exercises an attractive force as far as the sun, without any medium or means.”

  It was Newton’s notion of “action at a distance” that particularly galled Leibniz and many others. Newton agreed that there was no resolving this riddle, at least for the time being, but he put it to one side. “Mysterious though it was,” historian John Henry writes, by way of summarizing Newton’s view, “God could make matter act at a distance—to deny this was to deny God’s omnipotence.”

  The skeptics were not so easily satisfied. Without some mechanism that explained how physical objects pulled one another, they insisted, this new theory of universal gravitation was not a step forward but a retreat to medieval doctrines of “occult forces.” Proper scientific explanations involved tangible objects physically interacting with other tangible objects, not a mysterious force that flung invisible, undetectable lassos across endless regions of space. Invoking God, said Leibniz, was not good enough. If gravity was a force that God brought about “without using any intelligible means,” then that would not make sense “even if an angel, not to say God himself, should try to explain it.”

  Nor was the mystery merely that gravity operated across vast distances. Unlike light, say, gravity could not be blocked or affected in any way whatsoever. Hold your hand in front of your eyes and the light from a lamp on the other side of the room cannot reach you. But think of a solar eclipse. The moon passes between the Earth and the sun and blocks the sun’s light, but it certainly doesn’t block the gravitational force between Earth and sun—the Earth doesn’t fly out of its orbit. The force seems to pass through the moon as if it weren’t there.

  The closer you examined Newton’s theory, the more absurd it seemed. Consider, for instance, the Earth in its orbit. It travels at a fantastic speed, circling the sun at about 65,000 miles per hour. According to Newton, it is the sun’s gravitational pull that keeps the Earth from flying off into space. Now imagine a giant standing atop the sun and swinging the Earth around his head at that same speed of 65,000 miles per hour. Even if the titan held the Earth with a steel cable as thick as the Earth itself, the steel would snap at once, and Earth would shoot off into the void. And yet, with no sort of cable at all, gravity holds the Earth in an unbreakable grip.

  Seen that way, gravity seems incredibly powerful. But compared with nature’s other forces, like electricity and magnetism, it is astonishingly feeble. If you hold a refrigerator magnet a tiny distance from the fridge, the magnet leaps through the air and sticks to the door. Which is to say, the magnetic pull of a refrigerator door outmuscles the gravitational pull of the entire Earth.

  It was just as hard to understand how gravity could cut instantaneously across the cosmos. Newton maintained that it took no time whatsoever, not the briefest fraction of a second, for gravity to span even the vastest distance. If the sun suddenly exploded, one present-day physicist remarks, then according to Newton the Earth would instantly change in its orbit. (According to Einstein, we would be every bit as doomed, but we would have a final eight minutes of grace, blithely unaware of our fate.)

  None of this made sense. Kepler and Galileo, the first great scientists of the seventeenth century, had toppled the old theories that dealt with an everyday, commonsensical world where carts grind to a halt and cannonballs fall to Earth. In its place they began to build a new, abstract work of mathematical architecture. Then Newton had come along to complete that mathematical temple.

  So far, so good. Other great thinkers of the day, such men as Leibniz and Huygens, shared those mathematical ambitions. But when those peers and rivals of Newton looked closely at the Principia, they drew back in shock and distaste. Newton had installed at the heart of the mathematical temple not some gleaming new centerpiece, they cried, but a shrine to ancient, outmoded, occult forces.

  Curiously, Newton fully shared the misgivings about gravity’s workings. The idea that gravity could act across vast, empty stretches of space was, he wrote, “so great an absurdity that I believe no man who has in philosophical matters any competent faculty of thinking can ever fall into it.” He returned to the point over the course of many years. “To tell us that every Species of Things is endow’d with an occult specific Quality [like gravity] by which it acts and produces manifest Effects, is to tell us nothing.”

  Except . . . except that the theory worked magnificently. Newton’s mathematical laws gave correct answers—fantastically accurate answers—to questions that had long been out of reach, or they predicted findings that no one had ever anticipated. No one until Newton had explained the tides, or why there are two each day, or why the Earth bulges as it does, or why the moon jiggles as it orbits the Earth.

  Description and prediction would have to do, then, and explanation would have to wait. How the universe managed to obey the laws he had discovered—how gravity could possibly work—Newton did not claim to know. He would not guess.

  He painted himself as the voice of hardheaded reason, Leibniz as the spokesman for airy speculation. When Leibniz rebuked him for proposing so incomplete a theory, Newton maintained that restraint was only proper. He would stick to what he could know, even though Leibniz talked “as if it were a Crime to content himself with Certainties and let Uncertainties alone.” Newton opted for caution. “Ye cause of gravity is what I do not pretend to know,” he wrote in 1693, “& therefore would take more time to consider of it.”

  Twenty years later, he had made no progress. “I have not been able to discover the cause of those properties of gravity,” Newton wrote in 1713, “and I frame no hypotheses.” Another two centuries would pass before Albert Einstein framed a new hypothesis.

  In the meantime, Newton declared his peace with his own considerable achievement. “And to us it is enough that gravi
ty does really exist, and act according to the laws which we have explained,” he wrote, in a kind of grand farewell to his theory, “and abundantly serves to account for all the motions of the celestial bodies, and of our sea.”

  Chapter Fifty-Two

  In Search of God

  A different feature of Newton’s theory of gravitation raised the most troubling question of all: where did God fit into Newton’s universe? For seventeenth-century thinkers in general, and for Newton in particular, no question could have been more important. Today, the talk of God may seem misplaced. The Principia is not a sacred text but a scientific work that makes specific, quantitative predictions about the world. Those predictions are either true or false, regardless of what your religious views happen to be.53 But to judge the Principia by the accuracy of its predictions is to see only part of it. In a similar sense, you can admire Michelangelo’s Pietà as a gorgeous work of art even if you have no religious beliefs whatsoever. But to know what Newton thought he was doing, or Michelangelo, you need to take account of their religious motivation.

  Newton had ambitions for his discoveries that stretched far beyond science. He believed that his findings were not merely technical observations but insights that could transform men’s lives. The transformation he had in mind was not the usual sort. He had little interest in flying machines or labor-saving devices. Nor did he share the view, which would take hold later, that a new era of scientific investigation would put an end to superstition and set men’s minds free. Newton’s intent in all his work was to make men more pious and devout, more reverent in the face of God’s creation. His aim was not that men rise to their feet in freedom but that they fall to their knees in awe.

  So for Newton himself, the answer to the question where does God fit in the universe? was plain. God sat enthroned at the center of creation. Newton had always known it; he had always seen his work as a hymn to God’s glory, though one written in curves and equations rather than notes on a staff. Now his dazzling success in the Principia provided still further evidence of the magnificence of God’s design.

  But the great irony of Newton’s life was that many people looked at his work and drew precisely the opposite moral. Newton had not honored God, they insisted, but had made Him irrelevant. The more the universe followed laws that held everywhere and always, the less room God had to exercise his sovereignty. This critique was seldom directed at Newton personally (except by Leibniz). No one questioned the sincerity of his religious faith. Both his major works, the Principia and the Opticks, concluded with long, heartfelt outpourings of praise for the Creator. “He is eternal and infinite, omnipotent and omniscient,” Newton wrote in the Principia. “That is, his duration reaches from eternity to eternity; his presence from infinity to infinity; he governs all things and knows all things that are or can be done.”

  Still, the faithful insisted, Newton had inadvertently given aid and comfort to the enemy. He had bolstered the cause of science, and science had shown itself to be an enterprise devoted to demoting God. Everyone knew that the history of religion was filled with miraculous interventions—floods, burning bushes, the sick healed, the dead returned to life. God did not merely watch his creation. On countless occasions He had stepped in and directly altered the course of events. And now, it seemed, science threatened to push God aside.

  This made for a debate over gravity that in some ways anticipated the nineteenth-century battle over evolution. Such fights may seem to turn on arcane issues—planets and mathematical laws, fossils and apes—but in intellectual history, giant wars are fought on narrow battlegrounds. The real issue is always man’s place in the cosmos.

  Like evolution, gravity raised questions that tangled up science, politics, and theology. By hemming in God, religious thinkers railed, science promoted atheism. Atheist, in the seventeenth century, was an all-purpose slur that embraced a range of suspicious beliefs, much as commie or pinko would in Cold War America. But the fear it exposed was real, for to challenge religion was to call the entire social order into question. “Is nothing sacred?” was not an empty bit of rhetoric but a howl of anguish. If religion were undermined, sexual license and political anarchy were sure to follow.

  Nor did science aim only at toppling age-old beliefs. Even worse, in the eyes of its detractors, the new thinkers meant to replace time-honored doctrines with their own dubious substitutes. “Scientists, like whoring Jerusalem and Babylon, have turned away from God and have put in His stead their own systems and explanations,” writes one modern historian, in summarizing the antiscience case. “And these are the idols they worship: not the world created by God, but the mechanistic representations—like idols, devoid of spirit—that are the works of their own crazed imaginations.”

  If the universe was a machine, as science seemed to teach, then humans were just one more form of matter and there was no such thing as the soul, or choice, or responsibility. In such a world, morality would have no meaning, and, everyone would know, as one appalled writer put it, that “they may do any thing that they have a mind to.”

  So Newton and Leibniz squared off one last time, this time in an ideological clash over God and gravity. The battleground was the issue of God’s intervention in the world. Each man accused the other of maligning God and attacking Christianity. Newton began by insisting that his theory of gravitation did have an explicit role for God. It was not simply that, at creation, God had set the whole solar system in motion. More than that, He had continued ever since to fine-tune His creation. The planets could not be left to run on their own, Newton’s calculations showed; their ever-changing pulls on one another meant that their orbits were not quite stable. Left unattended, the solar system would fall out of kilter and, eventually, tumble into chaos.

  And so the world had not been left unattended. This was, Newton maintained, still further proof of God’s wisdom. If He had designed the universe to run unsupervised, He would have left room for the foolish and skeptical to argue that if God is absent now, perhaps He was absent always. God had known better.

  The question of whether God had neglected his creation was so touchy that Newton’s followers produced a second argument to demonstrate His ongoing presence. The miracles recorded in the Bible had taken place long ago. How to show that the age of miracles had not passed?

  One way was to update the definition of miracle. God continued to intervene in the world, argued the theologian William Whiston, speaking on Newton’s behalf, though perhaps He had changed His style. Even as familiar a feature of our lives as gravity “depends entirely on the constant and efficacious and, if you will, the supernatural and miraculous Influence of Almighty God.” There was nothing inherent in the nature of rocks that caused them to fall; they fell because God made them fall. If you stopped to think about it, wrote Whiston, it was as miraculous for a stone to drop to the ground as it would be for it to hover in midair.

  Leibniz pounced. Newton had committed heresy. Both Leibniz and Newton believed in a clockwork universe, but now Leibniz invoked the familiar image to mock his old enemy. “Sir Isaac Newton, and his followers, have also a very odd opinion concerning the work of God. According to their doctrine, God Almighty wants to wind up his watch from time to time: otherwise it would cease to move. He had not, it seems, sufficient foresight to make it a perpetual motion.”

  Newton fired back in fury. He was not the one blaspheming God. To call for a clock that ran forever on its own, as Leibniz had, was to cut God out of the picture. “If God does not concern himself in the Government of the World,” declared Samuel Clarke, another of Newton’s allies, “. . . it will follow that he is not an Omnipresent, All-powerful, Intelligent and Wise Being; and consequently, that he Is not at all.”

  Newton and Clarke were far from done. This dangerous doctrine of Leibniz’s posed a threat not only to Christianity but to political stability as well. To hear Leibniz tell it, the king of the universe was a mere figurehead and not a ruler at all. Think what that meant! “If a king had a king
dom wherein all things would continually go on without his government or interposition,” wrote Clarke, then he would not “deserve at all the title of king or governor.” Who would need such a do-nothing king? Leibniz had allied himself with those scoundrels of whom it “may reasonably be suspected that they would like very well to set the king aside.”

  Leibniz did not back down. If the cosmos needed constant tinkering, as Newton would have it, then God had not fully understood a design of His own making. This was to malign God, to charge our perfect Creator with imperfection.

  Deeply religious though both Newton and Leibniz were, they managed to talk past one another. The problem was that they focused on different aspects of God’s greatness. Newton emphasized God’s will, His ability to act however and whenever He chose. Leibniz focused on God’s wisdom, His ability to see ahead of time exactly how every conceivable event would play itself out, down the furthest corridors of time.

  That left both these brilliant, devout men caught in traps of their own making. Each had, in a sense, explained too much. Newton wanted above all else to portray God as a participant in the world, not a spectator. But Newton’s universe seemed to run by itself, despite his protests to the contrary. That made God a kind of absentee landlord. Leibniz, on the other hand, took as his unbreachable principle the notion of God as all-powerful and all-knowing. The catch was that a God with those traits had no choice but to throw a switch that set in motion precisely the world we have.

  The problem was that both were guilty as charged, and neither could admit it. Stuck defending indefensible positions, they fought to the death.

  Chapter Fifty-Three

  Conclusion