Description
In the beginning was Philosophy, and Philosophy was with Science, and Science was Philosophy. Philosophy shineth in darkness; and the darkness comprehended it not.
But then Philosophy begat children. And the children were many and very successful.
Already in the 6th Century the philosopher Boethius mentioned the three liberal arts of the Trivium,1 i.e. grammar, logic and rhetoric, and the four arts of the Quadrivium,2 i.e. arithmetic, geometry, music and astronomy. In addition, there were the practical arts, such as medicine and architecture. Later came the division into subjects or disciplines as we know them today, such as physics, chemistry, biology, psychology, etc. In the same manner as a most generous mother, Philosophy divested herself of most of her possessions in favour of her children.
Humans, being human, attribute to themselves the mission of trying to under-stand the nature of the wonderful and complex world in which they happen to live. For such a quest they utilize epistemological tools, which can be either a priori, i.e. within oneself, or a posteriori, i.e. outside oneself. For the sake of an easy classi-fication, we call mathematics the former and science the latter. Mathematics itself is not a science, yet it constitutes an invaluable tool for science, since it provides the means to interpret the reality we observe and a methodology to search for the underlying governing laws (assuming as a working conjecture that such laws exist and are immutable).
What Is Physics?
Among all scientific disciplines, physics is ideally suited to the task of discovering the laws of nature, since it deals with everything from the smallest particles (electrons or neutrinos), to the largest known entities (galaxies, clusters of galaxies, or even the universe itself): see Fig. 1.1. Physics also encompasses an astonishing range of times: see Fig. 1.2. There is, however, a remarkable region at sizes around 10−8 m, i.e. at the molecular level, which is predominantly within the domain of chemistry. This does not mean that molecular physics is not relevant for physicists. It is, but at that level, chemical reactions, which are extremely important both from an applicative and a theoretical point of view, are prevalent and they can best be studied with a very different methodology (that of chemistry). In the last few decades, however, the development of applied Quantum Mechanics has allowed the two converging disciplines of physical chemistry and chemical physics to emerge.
A subfield of chemistry, organic chemistry, has its own basic relevance, since it is a prerequisite to the understanding of life, i.e., to biology (although not to an understanding of how life originated, which still remains a very open question). Life itself appears in a wide variety of forms. In fact an estimated number of 10 million species fill the realms of fauna and flora (in addition to more primitive forms of life), spanning about eight orders of magnitude in their linear dimensions and 24 in their masses (see Fig. 1.1).
To appreciate the range of our task in this book, it may be helpful to look at how the field of physics is subdivided (see Fig. 1.3). A caveat, however, is needed, since the various branches are interlaced by means of a thick and ever expanding network of links, which are by necessity omitted in the figure. In addition, Universality, a conjectured, but not yet well investigated property of the physical world, foretells the emergence of other similarities and analogies among apparently unrelated phenomenologies (see Chap. 12).