Über die Autorin bzw. den Autor

Charis Anastopoulos is a researcher in the Department of Physics at the University of Patras in Greece.

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"A highly intelligent book by someone who has thought deeply about the fundamentals of physics. Its aim is to convey to a mixed audience how the successful and well-established quantum theory of fields goes about describing nature. This book has deepened my understanding. I enjoyed it and I think others will too."--David Park, professor emeritus, Williams College

"A significant contribution to the popular literature on physics. This book elucidates for a general reader the concept of matter and how this concept has evolved over the centuries from philosophical ideas of classical antiquity to the abstract concepts of relativity and quantum physics. The author writes a good narrative."--Mark P. Silverman, Trinity College

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Particle or Wave

Princeton University Press

Introduction

If we ask individuals from a Western society to ponder the meaning of the word "matter" (in the sense of material), they will probably come up with many different images. They may think about the atoms and all the tiny particles that have been discovered by modern science. Or perhaps they will think about the successes of technology in controlling and manipulating all different types of material processes and then consider how this affects their everyday life. They may also realize that they are themselves material beings and will inevitably remember the oldest of contrasts, "mind vs. matter," or perhaps "mind over matter." Or they may be quick to think in moral terms and focus on the distinction between the "person of spirit" and the "person of matter." One way or another, the word "matter" will have a meaning for them-perhaps not a unique or an unambiguous one, but they will definitely conclude that it refers to something so fundamental as to be really important.

We may next imagine asking the same question to people of other cultures and times. We will have to find an appropriate word in their language to translate "matter." It is rather remarkable-given the immense diversity of living and dead languages-that most of the time we will be able to find an adequate translation. The corresponding word may not have exactly the same connotations-the idea of atoms would hardly come into the mind of a person unfamiliar with modern science, or at least with a developed philosophical tradition. There may also exist fine differences of meaning between these words. Still, any person who understands the question will not fail to think of matter as the substance manipulated with one's hands, however primitive the technology may be. After all, humans are and have always been toolmakers and tool users. And neither will the person fail to grasp the distinction between matter and mind because this is akin to a distinction familiar to every human being, that between the things of the outside world that we perceive through our senses and the emotions and thoughts of our internal life.

It follows, then, that "matter" is an abstraction common to people of different times and cultures. It arises out of the one single thing that a modern person shares with a Greek of Plato's times, a tribesman of New Guinea, and a courtier of the Forbidden City: our common humanity in the way we sense, feel, act, and live our lives in the world. Matter is therefore a universal concept. A magician of old times would not hesitate to call it a "word of power"; a modern psychologist would perhaps prefer the word "archetype." Of course "matter" is not the only such word: time and space, emotion and reason, divine and profane, multiplicity and unity, flux and immobility, cause and effect, psyche and matter-all these are ideas that resonate in the thoughts and languages of all times, and their significance is explored in the people's philosophies, myths, religion, songs, or dreams. There exist differences of meaning, of course. One concept may be understood differently in different cultures. But no matter how important such differences may be, they do not affect the essence of the fundamental concepts. These concepts are perceived at a deep level of the human psyche, before any association to words, logical definitions, or social practices. At that level, they are the same everywhere because they refer to an experience of reality common to all people.

In modern societies, however, the study of matter is perceived to be a prerogative of the sciences, mainly physics. Indeed, the development of physics during the last couple of centuries has provided deep insight into the deepest structure and organization of matter. The success of the scientific method has been so overwhelming that by the end of the twentieth century many scientists did not hesitate to make an astonishing claim that it is only a matter of time before we construct a "theory of everything."

The scientific description of the world, however, does not grow in a vacuum. It is equally impossible to detach the concepts of science from ideas, perceptions, and feelings that arise in other fields of human culture. Scientific concepts may be presented in their final form detached, self-contained, and logically complete, but this is mostly an outward appearance, similar to the precise, clean-cut, and orderly performance given by a military unit during an inspection by their commander in chief. In reality, the concepts of science and the thoughts of scientists are immersed in the ocean of the society people live in, and their origins are blended with a myriad of other ideas, images, and thoughts. This is the reason that even an account of the scientific theories of matter cannot be restricted to the scientific theories themselves but has to seek their roots in other fields of human activity.

History also plays an important role. Hermann Weyl, one of the greatest mathematicians of the past century, has remarked that it is impossible to understand the character of modern mathematics unless it is considered in the perspective of its history over the last two thousand years. The same is also true for modern physical theories, and even more emphatically so. Mathematical concepts are abstract by nature, while the physical ones have a more earthly character. They are more closely related to the concrete experience of the senses and the way the world is perceived in different times and places. Indeed, mathematical purists are often exasperated with the ambiguous character of the physical concepts, which still seem to carry the "dirt" of their lowly origins.

If we follow Weyl's advice in the context of modern physics and attempt to trace back in time the origin of the modern physical concepts about matter, we see that they arise from two conflicting theories, whose seeds in art and myth are probably lost in the mists of prehistory. These theories were first explicitly stated and rationally analyzed in Greece during the fifth century b.c. The first of these theories is the atomic theory; it describes matter as consisting of discrete, indivisible pieces, which move in the void and through their motion create all things that come into our perception. Indeed, even the human soul consists of such particles, finer in their form than the ones of ordinary matter. The motion of these atoms is due to a necessity external to them, which determines precisely and unambiguously how and toward which direction each atom will move. Everything that we see in the world may be analyzed in terms of the distinctive properties of the atoms and their motion in the void; nothing else exists-all other images are simply figments of our imagination.

In opposition to the atomic theory stands the theory of the elements. Matter, it proposes, consists of elementary substances (the elements), which are distinguished from each other by means of their intrinsic qualities. The elements are pure and simple; they represent elementary qualities and cannot be analyzed in simpler components. Initially only four such substances were postulated: Earth, Water, Air, and Fire. All material things that appear to our senses arise from the elements being blended together, and what we...