The God Particle

by Leon Lederman

  Gravity is our number-one problem as we attempt to combine particle physics with cosmology. Here we are like the ancient Greeks, waiting and watching for something to happen, not able to experiment. If we could slam two stars together instead of two protons, then we'd see some real effects. If the cosmologists are right and the Big Bang is really a good theory—and I was assured recently at a meeting that it's still a good theory—then at some early phase all the particles in the universe were in a very small location. The energy per particle became huge. The gravitational force, strengthened by all that energy, which is equivalent to mass, becomes a respectable force in the domain of the atom. The atom is ruled by the quantum theory. Without bringing the gravitational force into the family of quantum forces, we'll never understand the details of the Big Bang or in fact, the deep, deep structure of elementary particles.

  ISAAC AND HIS ATOMS

  Most Newtonian scholars agree that he believed in a particle-like structure of matter. Gravity was the one force Newton treated mathematically. He reasoned that the force between bodies, whether they be earth and moon or earth and apple, must be a consequence of the force between constituent particles. I would hazard a guess that Newton's invention of the calculus is not unrelated to his belief in atoms. To understand the earth-moon force, for example, one has to apply our formula II. But what do we use for R, the earth-moon distance? If earth and moon were very small, there would be no problem in assigning R. It would be the distance between the centers of the objects. However, to know how the force of a very small particle of earth influences the moon and to add up all the forces of all the particles requires the invention of integral calculus, which is a way of adding an infinite number of infinitesimals. In fact, Newton invented calculus in and around that famous year, 1666, when the physicist claimed his mind was "remarkably fit for invention."

  In the seventeenth century there was precious little evidence for atomism. In the Principia, Newton said we must extrapolate from sensible experiences to understand the workings of the microscopic particles that make up bodies: "Because the hardness of the whole arises from the hardness of the parts, we ... justly infer the hardness of the undivided particles not only of the bodies we feel but of all others."

  His research in optics led him, like Galileo, to interpret light as a stream of corpuscles. At the end of his book Opticks, he reviewed current ideas on light and took this breathtaking plunge:

  Have not the Particles of Bodies certain Powers, Virtues or Forces by which they act at a distance, not only on the rays of Light for reflecting, refracting, and inflecting them, but also upon one another for producing a great part of the phenomena of nature? For it is well known that bodies act on one another by the Attractions of Gravity, Magnetism, and Electricity, and these instances show the tenor and course of nature and make it not improbable that there may be more attractive powers than these ... others which reach to small distances as hitherto escape observations; and perhaps electrical attractions may reach to small distances even without being excited by Friction, [emphasis mine]

  Here is prescience, insight, and even, if you like, hints of the grand unification that is the Holy Grail of physicists in the 1990s. Was not Newton calling here for a search for forces within the atom, known today as the strong and weak forces? Forces that work only at "small distances," unlike gravity? He went on to write:

  All these things being considered, it seems probable to me that God in the Beginning formed matter in solid, massy, hard, impenetrable, moveable particles ... and these primitive particles being solids ... so very hard as never to wear out or break in pieces, no ordinary power being able to divide what God Himself made one in the first creation.

  The evidence was weak, but Newton set a course for physicists that would wind its way relentlessly toward the microworld of quarks and leptons. The quest for an extraordinary force to divide "what God himself made one" is the active frontier of particle physics today.

  SPOOKY STUFF

  In the second edition of Opticks, Newton hedged his conclusions with a series of Queries. These questions are so perceptive—and so open-ended—that one can find anything one wants in them. But it is not so far-fetched to believe that Newton may have anticipated, in some deeply intuitive way, the wave-particle duality of quantum theory. One of the most disturbing ramifications of Newton's theory is the problem of action at a distance. The earth pulls on an apple. It falls to the ground. The sun pulls on the planets; they orbit elliptically. How? How can two bodies, with nothing but space between them, transmit force to each other? One popular model of the time hypothesized an aether, some invisible and insubstantial medium pervading all space, through which object A could make contact with object B.

  As we shall see, the aether idea was seized upon by James Clerk Maxwell to carry his electromagnetic waves. This idea was destroyed by Einstein in 1905. But like Pauline's, aether's perils come and go, and today we believe that some new version of aether (really the void of Democritus and Anaximander) is the hiding place of the God Particle.

  Newton eventually rejected the notion of an aether. His atomistic view would have required a particulate aether, which he found objectionable. Also the aether would have to transmit forces without impeding the motion of, for example, the planets in their inviolate orbits.

  Newton's attitude is illustrated by this paragraph of his Principia:

  There is a cause without which these motive forces would not be propagated through the spaces round about; whether that cause be of some central body (such as a magnet in the center of the magnetic force), or anything else that does not yet appear. For I have design only to give a mathematical notion of these forces, without considering their physical causes and feats.

  At this, the audience, if they were physicists at a modern seminar, would stand up and cheer, because Newton hits the very modern theme that the test of a theory is its agreement with experiment and observation. So what if Newton (and his present-day admirers) didn't know Why gravity? What creates gravity? That is a philosophical question until someone shows that gravity is a consequence of some deeper concept, some symmetry perhaps of higher-dimensional space-time.

  Enough of philosophy. Newton advanced our quest for the a-tom enormously by establishing a rigorous scheme of predicting, of synthesis that could be applied to a vast array of physical, problems. As these principles caught on, they had, as we have seen, a profound influence on practical arts such as engineering and technology. Newtonian mechanics, and its new mathematics, is truly the base of a pyramid upon which all the layers of physical sciences and technology are built. Its revolution represented a change in the perspective of human thinking. Without this change, there would have been no industrial revolution and no continuing systematic search for new knowledge and new technology. This marks a transition from a static society waiting for something to happen to a dynamic society seeking understanding, knowing that understanding implies control. And the Newtonian imprint gave reductionism a powerful boost.

  Newton's contributions to physics and mathematics and his commitment to an atomistic universe are clearly documented. What remains misty is the influence on his scientific work of his "other life," his extensive research in alchemy and his devotion to occult religious philosophy, especially Hermetic ideas that harked back to ancient Egyptian priestly magic. These activities were very largely hidden. As Lucasian professor at Cambridge (Stephen Hawking is the current incumbent) and later as a member of the London political establishment, Newton could not let his devotion to these subversive religious practices be known, for that would have brought him extreme embarrassment if not total disgrace.

  We may leave the last comment on Newton's work to Einstein:

  Newton, forgive me; you found the only way which, in your age, was just about possible for a man of highest thought—and creative power. The concepts, which you created, are even today still guiding our thinking in physics, although we now know that they will have to be replaced by others farther remov
ed from the sphere of immediate experience, if we aim at a profounder understanding of relationships.

  THE DALMATIAN PROPHET

  A final note on this first stage, the age of mechanics, the great era of classical physics. The phrase "ahead of his time" is overused. I'm going to use it anyway. I'm not referring to Galileo or Newton. Both were definitely right on time, neither late nor early. Gravity, experimentation, measurement, mathematical proofs ... all these things were in the air. Galileo, Kepler, Brahe, and Newton were accepted—heralded!—in their own time, because they came up with ideas that the scientific community was ready to accept. Not everyone is so fortunate.

  Roger Joseph Boscovich, a native of Dubrovnik who spent much of his career in Rome, was born in 1711, sixteen years before Newton's death. Boscovich was a great supporter of Newton's theories, but he had some problems with the law of gravitation. He called it a "classical limit," an adequate approximation where distances are large. He said that it was "very nearly correct but that differences from the law of inverse squares do exist even though they are very slight." He speculated that this classical law must break down altogether at the atomic scale, where the forces of attraction are replaced by an oscillation between attractive and repulsive forces. An amazing thought for a scientist in the eighteenth century.

  Boscovich also struggled with the old action-at-a-distance problem. Being a geometer more than anything else, he came up with the idea of fields of force to explain how forces exert control over objects at a distance. But wait, there's more!

  Boscovich had this other idea, one that was real crazy for the eighteenth century (or perhaps any century). Matter is composed of invisible, indivisible a-toms, he said. Nothing particularly new there. Leucippus, Democritus, Galileo, Newton, and others would have agreed with him. Here's the good part: Boscovich said these particles had no size; that is, they were geometrical points. Clearly, as with so many ideas in science, there were precursors to this—probably in ancient Greece, not to mention hints in Galileo's works. As you may recall from high school geometry, a point is just a place; it has no dimensions. And here's Boscovich putting forth the proposition that matter is composed of particles that have no dimensions! We found a particle just a couple of decades ago that fits such a description. It's called a quark.

  We'll get back to Mr. Boscovich later.

  4. STILL LOOKING FOR THE ATOM: CHEMISTS AND ELECTRICIANS

  The scientist does not defy the universe. He accepts it. It is his dish to savor, his realm to explore; it is his adventure and never-ending delight. It is complaisant and elusive but never dull. It is wonderful both in the small and in the large. In short, its exploration is the highest occupation for a gentleman.

  —I.I. Rabi

  AN ADMISSION: the physicists haven't been the only ones searching for Democritus's atom. Chemists have certainly made their mark, especially during the long era (circa 1600–1900) that saw the development of classical physics. The difference between chemists and physicists is not really insurmountable. I started out as a chemist but switched to physics partly because it was easier. Since then I have frequently noted that some of my best friends talk to chemists.

  The chemists did something that the physicists before them hadn't done. They did experiments relevant to atoms. Galileo, Newton, et al., despite their considerable experimental accomplishments, dealt with atoms on a purely theoretical basis. They weren't lazy; they just didn't have the equipment. It was up to the chemists to conduct the first experiments that made atoms reveal their presence. In this chapter we'll dwell on the rich experimental evidence that supported the existence of Democritus's a-tom. We'll see many false starts, some red herrings, and misinterpreted results, always the bane of the experimenter.

  THE MAN WHO DISCOVERED NINE INCHES OF NOTHING

  Before we get to the hard-core chemists, we must mention one scientist, Evangelista Torricelli (1608–1647), who bridged the gap between the mechanics and the chemists in the attempt to restore atomism as a valid scientific concept. To repeat, Democritus said, "Nothing exists except atoms and empty space; everything else is opinion." Thus, to prove the validity of atomism, you need atoms, but you also need empty space between them. Aristotle opposed the very idea of a vacuum, and even during the Renaissance the Church continued to insist that "nature abhors a vacuum."

  That's where Torricelli came in. He was one of Galileo's disciples in that scientist's latter days, and in 1642 Galileo set him to work on a problem. The Florentine well diggers had observed that in suction pumps water will not rise more than 10 meters. Why should this be? The initial hypothesis, advanced by Galileo and others, was that vacuum was a "force" and that the partial vacuum produced by the pumps propelled the water upward. Galileo obviously didn't want to be personally bothered with the well diggers' problem, so he delegated it to Torricelli.

  Torricelli figured out that the water was not being pulled up by the vacuum at all, but rather pushed up by normal air pressure. When the pump lowers the air pressure above the column of water, the normal air outside the pump pushes down harder on the ground water, forcing water in the pipe upward. Torricelli checked out his theory the year after Galileo died. He reasoned that since mercury is 13.5 times denser than water; air should be able to lift mercury only 1/13.5 times as high as water—or about 30 inches. Torricelli obtained a thick glass tube about 1 meter (about 39 inches) long that was closed at the bottom, open at the top, and did a simple experiment. He filled the tube to the brim with mercury, covered the top with a stopper, then turned the tube upside down, placed it in a bowl of mercury and pulled out the stopper. Some of the mercury poured down out of the tube into the dish. But as Torricelli had predicted, 30 inches of the liquid metal remained in the tube.

  This pivotal event in physics is often referred to as the invention of the first barometer, which of course it was. Torricelli noted that the height of the mercury varied from day to day, measuring fluctuations in the atmospheric pressure. For our purposes, however, there was a greater significance. Let's forget about the 30 inches of mercury filling up most of the tube. What's important to us is those 9 odd inches at the top. Those few inches at the top of the tube—the closed end—contained nothing. Really nothing. No mercury, no air, nothing. Well, hardly anything. It's a fair vacuum, but it contains some mercury vapor, the amount depending on the temperature. The vacuum is about 10−6 torn (A tort; after Evangelista, is a measure of pressure; 10−6 torr is about one billionth of the normal pressure of the atmosphere.) Modern pumps can get to 10−11 torr and better. In any case, Torricelli had attained the first artificially created high-quality vacuum. There was no backing off from this conclusion. Nature may or may not abhor a vacuum, but she has to put up with it. Now that we had proved the existence of empty space, we needed some atoms to put there.

  SQUEEZING GAS

  Enter Robert Boyle. This Irish-born chemist (1627–1691) was criticized by his peers for being too much a physicist and too little a chemist in his way of thinking, but clearly his accomplishments belong primarily to the realm of chemistry. He was an experimentalist whose experiments often came to naught, yet he advanced the idea of atomism in England and on the continent. He was sometimes known as the Father of Chemistry and the Uncle of the Earl of Cork.

  Influenced by Torricelli's work, Boyle became fascinated with vacuums. He hired Robert Hooke, the same Hooke who loved Newton so much, to build an improved air pump for him. The air pump inspired an interest in gases, which Boyle came to realize were a key to atomism. He may have had some help here from Hooke, who pointed out that the pressure a gas exerts on the walls of its container—such as air straining against the sides of a balloon—might result from a torrent of atoms. We don't see individual indentations from the atoms inside a balloon because there are billions and billions of them, which simulate a smooth outward push.

  Like Torricelli's, Boyle's experiment involved mercury. Taking a seventeen-foot, J-shaped tube, he sealed the short end; then he poured mercury into the lo
ng open end to close off the bottom curve of the J. He then continued to add mercury to the open end. The more he poured, the smaller the space available for the air trapped in the short end. Correspondingly, the air pressure in the small volume increased, as he could easily measure by the extra height of mercury in the open end of the tube. Boyle discovered that the volume of the gas varied inversely with the pressure on it. The pressure on the gas trapped in the closed end results from the extra weight of the mercury plus the atmosphere pushing down on the open end. If he doubled the pressure by adding mercury, the volume of air decreased to one half.