It is difficult to venture into the world of the ultimately small, or even to talk about it, without a very good understanding of the laws of Nature that govern that world. The forces one finds there determine the way in which the tiny particles we wish to study move about, and also all their other properties. Whether, and how, we can actually observe them will also depend on these forces. And this is not easy, because the laws of Nature are complicated. More and more experts in this field seek refuge in a kind of mathematical gibberish no ‘normal’ person can follow, unless he or she belongs to the in-crowd. To really appreciate the rock-solid logic of the laws of physics, one actually cannot avoid math. Nonetheless, we physicists feel the need to share the joy of all our beautiful discoveries with whoever wants to listen. We are advised then to avoid all math. This then is what I shall reluctantly do. It is my intention to provide a narrative of twenty-five years of research on the very tiniest particles of matter. During those twenty-five years, I began to view Nature as an intelligence test to which humanity as a whole has been subjected, as a giant jigsaw puzzle given to us to play with. Time and again, we stumble upon new pieces, large or small, that fit beautifully with those we already have. I want to share with you the sense of triumph we feel at such moments.
It is difficult to venture into the world of the ultimately small, or even to talk about it, without a very good understanding of the laws of Nature that govern that world. The forces one finds there determine the way in which the tiny particles we wish to study move about, and also all their other properties. Whether, and how, we can actually observe them will also depend on these forces. And this is not easy, because the laws of Nature are complicated. More and more experts in this field seek refuge in a kind of mathematical gibberish no ‘normal’ person can follow, unless he or she belongs to the in-crowd. To really appreciate the rock-solid logic of the laws of physics, one actually cannot avoid math. Nonetheless, we physicists feel the need to share the joy of all our beautiful discoveries with whoever wants to listen. We are advised then to avoid all math. This then is what I shall reluctantly do. It is my intention to provide a narrative of twenty-five years of research on the very tiniest particles of matter. During those twenty-five years, I began to view Nature as an intelligence test to which humanity as a whole has been subjected, as a giant jigsaw puzzle given to us to play with. Time and again, we stumble upon new pieces, large or small, that fit beautifully with those we already have. I want to share with you the sense of triumph we feel at such moments.
Abstract In the first quarter of this century physicists were slowly and somewhat reluctantly forced to realize that the view of the physical world, so painstakingly built up over the preceding four centuries, was in serious need of revision. In particular, the laws that governed the motion of particles on the atomic scale were not those of classical mechanics. Physics found itself catapulted into the strange new world of quantum theory in which the very notion of position or velocity of a particle became blurred and statistical laws dominated everything.
Primitive man must have found nature singularly puzzling and intricate. The simplest phenomena could be trusted to recur indefinitely; an unsupported body invariably fell, a stone thrown into water sank, while a piece of wood floated. Yet other more complicated phenomena shewed no such uniformity—the lightning struck one tree in the grove while its neighbour of similar growth and equal size escaped unharmed; one month the new moon brought fair weather, the next month foul. Confronted with a natural world which was to all appearances as capricious as himself, man's first impulse was to create Nature in his own image; he attributed the seemingly erratic and unordered course of the universe to the whims and passions of gods, or of benevolent or malevolent lesser spirits. Only after much study did the great principle of causation emerge. In time it was found to dominate the whole of inanimate nature: a cause which could be completely isolated in its action was found invariably to produce the same effect. What happened at any instant did not depend on the volitions of extraneous beings, but followed inevitably by inexorable laws from the state of things at the preceding instant. And this state of things had in turn been inevitably determined by an earlier state, and so on indefinitely, so that the whole course of events had been unalterably determined by the state in which the world found itself at the first instant of its history; once this had been fixed, nature could move only along one road to a predestined end.
This book is written with the graduate student in mind. I had in mind to write a text that would introduce my students to the basic ideas and concepts behind many-body physics. At the same time, I felt very strongly that I would like to share my excitement about this field, for without feeling the thrill of entering uncharted territory I do not think one has the motivation to learn and to make the passage from learning to research. Traditionally, as physicists we ask “what are the microscopic laws of nature?”, often proceeding with the brash certainty that, once revealed, these laws will have such profound beauty and symmetry that the properties of the universe at large will be self-evident. This basic philosophy can be traced from the earliest atomistic philosophy of Democritus to the most modern quests to unify quantum mechanics and gravity. The dreams and aspirations of many-body physics interwine the reductionist approach with a complementary philosophy: that of emergent phenomena . In this view, fundamentally new kinds of phenomena emerge within complex assemblies of particles which cannot be anticipated from an a priori knowledge of the microscopic laws of nature. Many-body physics aspires to synthesize, from the microscopic laws, new principles that govern the macroscopic realm, asking: What emergent principles and laws develop as we make the journey from the microscopic to the macroscopic? This is a comparatively modern and far less familiar scientific philosophy. Charles Darwin was perhaps the first to seek an understanding of emergent laws of nature. Following in his footsteps, Ludwig Boltzmann and James Clerk Maxwell were among the first physicists to appreciate the need to understand how emergent principles are linked to microscopic physics. From Boltzmann's biography [1], we learn that he was strongly influenced and inspired by Charles Darwin. In more modern times, a strong advocate of this philosophy has been Philip W. Anderson, who first introduced the phrase “emergent phenomenon” into physics. In an influential article entitled “More is different,” written in 1967 [2], he captured the philosophy of emergence, writing: The behavior of large and complex aggregations of elementary particles, it turns out, is not to be understood in terms of a simple extrapolation of the properties of a few particles.[…]
Abstract As the end of the nineteenth century, the search for Nature’s basic laws seemed close to its goal. There was a sense of a task accomplished. Physics presented an orderly scene that fit the proper Victorian mood of the day. Objects both on Earth and in the heavens behaved in accord with Newton’s laws. So, presumably, did atoms. The nature of atoms was unclear. But to most scientists the rest of the job of describing the universe seemed a filling in of the details of the Great Machine.
Copenhagen is the perfect setting for our discussion of matter and information. We have been charged ‘to explore the current concept of matter from scientific, philosophical, and theological perspectives’. The essential foundation for this work is the output of the intense intellectual struggles that took place here in Copenhagen during the twenties, principally between Niels Bohr, Werner Heisenberg, and Wolfgang Pauli. Those struggles replaced the then-prevailing Newtonian idea of matter as ‘solid, massy, hard, impenetrable, moveable particles’ with a new concept that allowed, and in fact demanded, entry into the laws governing the motion of matter of the consequences of decisions made by human subjects. This change in the laws swept away the meaningless billiard-ball universe, and replaced it with a universe in which we human beings, by means of our intentional effort, can make a difference in how the ‘matter’ in our bodies behaves. THE ROLE OF MIND IN NATURE Unfortunately, most of the prevailing descriptions of quantum theory tend to emphasize puzzles and paradoxes in a way that makes philosophers, theologians, and even non-physicist scientists leery of actually using in any deep way the profound changes in our understanding of human beings in nature wrought by the quantum revolution. Yet, properly presented, quantum mechanics is thoroughly in line with our deep human intuitions. It is the 300 years of indoctrination with basically false ideas about how nature works that now makes puzzling a process that is completely in line with normal human intuition.
A physics-based understanding of how our conscious thoughts can affect our physically described brains is presented. This understanding depends on the shift from the mechanical conception of nature that prevailed in science from the time of Isaac Newton until the dawn of the twentieth century to the psychophysical conception that emerged from the findings of Planck, Bohr, Heisenberg, and von Neumann. This shift converted the role of our conscious thoughts from that of passive observers of a causally closed physically described universe to that of active participants in an essentially psychophysical understanding of nature. 1. The Basic Question and Why It Is Important. Science’s conception of the physical world changed radically during the twentieth century. At the end of the nineteenth century most scientists still viewed the physical universe as essentially a giant machine. This mechanical view emerged from the seventeenth century work of Isaac Newton, who built his conception of nature on the ideas of Rene Descartes. According to Descartes, the universe is composed of two kinds of elements, the first consisting of elements each of which occupies at each instant of time a definite region in space, and the second consisting of elements that include our human thoughts. Descartes allowed these two parts of nature to interact causally within our brains, but Newton specified that the motions of the elements of the first kind are completely determined by laws of motion that refer exclusively to elements of this kind. In Newtonian-type physics these elements of the first kind are, moreover, essentially mechanical, in the sense that they have been stripped of the experiential qualities that characterize our thoughts, such as the conscious awareness of feelings, and the capacity to grasp meanings. Consequently there is in Newtonian-type physics no possibility for any causally effective role for any aspects of our being that are essentially different in kind from the mechanical elements that occur in that type of physics. Descartes’ views accommodated our intuitive feeling that our conscious thoughts can influence our bodily movements – my conscious intent to raise my arm seems to cause my arm to rise – whereas Newton’s physics leads to the contrary conclusion that, in spite of what may seem to be the case, the notion that human thoughts, per se, can affect human actions is a deeply misleading illusion. Newton’s ideas led eventually to the classical physics of the late nineteenth century. Its main premises are these: 2 1. There exists a material universe that develops over the course of time by means of interactions of its tiny mechanical parts with neighboring tiny mechanical parts. 2. These interactions are governed by mathematical laws. 3. These laws entail that the mechanically described future is completely determined by the mechanically described past, with no reference to human thoughts, choices, or