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.
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.
So far, this book has dealt almost exclusively with classical physics, which is a theoretical structure based on many brilliant and imaginative experiments performed on macroscopic objects, that is on objects of about our size or a few orders of magnitude smaller or larger. Classical physics was found to give good results when extrapolated downward to molecules and upward to planets, stars, and galaxies, and it was seriously suggested ate in the nineteenth century that all the major discoveries in physics had been made — that the physical basis of the universe was understood and that only minor tidying-up remained.
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.
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
Those defile the purity of mathematical and philosophical truthy who confound real quantities with their relations and sensible measures. —ISAAC NEWTON, Principia Before we say anything about quantum mechanics, let us take a quick look at the Newtonian (or ‘classical’) view of the physical universe. According to that view, nature consists of an enormous number of particles. When Newtonian physics is combined with the theory of the electromagnetic field, it becomes convenient to think of these particles as dimensionless (even if there is a kind of conceptual strain involved in trying to think of something as having a mass but not any size ), and as possessing electrical properties – negative charge, or positive charge, or neutrality. This leads to the well-known ‘solar system’ view of the atom – with the electrons whirling around the nucleons (neutrons and protons) just as the planets whirl around the sun. Out of atoms are built molecules; out of molecules, macroscopic objects, scaling from dust motes to whole planets and stars. These latter also fall into larger groupings – solar systems and galaxies – but these larger structures differ from the ones previously mentioned in being held together exclusively by gravitational forces. At every level, however, one has trajectories (ultimately that means the possibility of continuously tracing the movements of the elementary particles) and one has causality (ultimately that means the possibility of extrapolating from the history of the universe up to a given time to its whole sequence of future states).
Twentieth-Century Physics A century which has run less than a third of its course has already witnessed two great upheavals in physical science. These are associated with the words Relativity and Quanta, and have forced the physicist of to-day to view nature against a background of ideas which is very different from that of his nineteenth-century predecessor. The latter thought of nature as an assemblage of objects located in space and continually changing with the passage of time. It was something entirely detached from, and external to, himself; something which he could study and explore from a distance as the astronomer studies the surface of the sun through his telescope, or the explorer the desert from his aeroplane. He thought of the apparatus of his laboratory as the astronomer thinks of his telescope, or the explorer of his field-glass; it shewed him things which were there whether he looked at them or not, which had been there before the first man appeared on earth, and would still be there after the last man had been frozen to extinction. Finally he accepted a “common-sense” view of nature, believing that there was no great difference between appearance and reality; the possibility that things were not as they seemed might provide an admirable subject for a debating society of philosophers, but was of as little practical concern to the scientist as to the farm-labourer. Although he may not have realised it, this complex of beliefs constituted a philosophical creed in itself.
Abstract A scientist in the late nineteenth century could be forgiven for thinking that the major elements of physics were built on unshakeable foundations and effectively established for all time. The inspirational work of Galileo Galilei and Isaac Newton in the seventeenth century had been shaped by a further 200 years of theoretical and, in particular, experimental science into a marvellous construction which we now call classical physics. This physics appeared to explain almost every aspect of the physical world: the dynamics of moving objects, thermodynamics, optics, electricity, magnetism, gravitation, etc. So closely did theory agree with and explain experimental observations of the everyday world that there could be no doubt about its basic correctness- its essential ‘truth’. Admittedly, there were a few remaining problems but these seemed to be trivial compared with the fundamentals - a matter of dotting a few is and crossing some ts.