CENTENNIAL CELEBRATION OF THE NATIONAL ACADEMY OF SCIENCES SECOND SCIENTIFIC SESSION October 22, 1963 NATURE OF MATTER CONTENTS INTRODUCTION . .. .. .Melvin Calvin, Chairman 955 SYMMETRY AND CONSERVATION LAWS ....... Eugene P. Wigner 956 ELEMENTARY PARTICLES ............. Geoffrey F. Chew 965 THE STRUCTURE OF NUCLEI . .. .. Victor F. Weisskopf 971 THE ARCHITECTURE OF MOLECULES . .. .Linus Pauling 977 THE ORGANIZATION OF LIVING MATTER . .. .George E. Palade * * The manuscript of this lecture has not been received. It will be published in the first issue possible follow- ing its receipt. INTRODUCTION BY MELVIN CALVIN DEPARTMENT OF CHEMISTRY, UNIVERSITY OF CALIFORNIA, BERKELEY I welcome you to the Second Scientific Session of the one-hundredth anniversary meeting of the National Academy of Sciences of the United States. Yesterday we heard a discussion of the history of the universe, in its many aspects, including the history of living things as we know them. Today we will be concerned with the very nature of the matter of which the things whose history we heard about yesterday is constructed. Our view of the nature of that matter has varied greatly ever since man began to wonder about its nature. Today we will undertake an examination of the present status of our concepts of its nature, at all levels of organization. In constructing the program, we were concerned about the order in which we should try to arrange it. And the very structure of our experience, as one of our speakers will describe, in a very real sense determines in some way our view of things. First we will concern ourselves not with any chronological sequence of our concepts either in universal time or human time, but rather with an examination of the concepts and materials at various levels of organization, beginning with the Axiom itself, which gives rise to the physical laws, and presumably there is more than one. In the very structure of these physical laws in turn, we arrive at the first particles which, for lack of a better name-following consultation with some 955 Downloaded by guest on September 28, 2021 956 CENTENNIAL: SECOND SCIENTIFIC SESSION PROC. N. A. S. of my colleagues, both theoretical and experimental-we may call Aons, for the leptons and baryons. We proceed from these to the particles of still higher degrees of order and structure, i.e., the atoms, both the nuclei and the electronic structure surrounding them. From here we proceed to a still higher degree of order. How are the atoms hooked together into aggregations, which we call molecules? And finally, how are the molecules put together into living structures, of which man might be considered one of the most complex representations. Thus, we have a series of four class-A speakers, beginning with one who speaks of the Axioms, one who speaks of the Aons, one who speaks of the Atoms, and one who speaks of the Aggregates of Atoms. SYMMETRY AND CONSERVATION LAWS BY EUGENE P. WIGNER PALMER PHYSICAL LABORATORY, PRINCETON UNIVERSITY Introduction.-Symmetry and invariance considerations, and even conservation laws, undoubtedly played an important role in the thinking of the early physicists, such as Galileo and Newton, and probably even before them. However, these considerations were not thought to be particularly important and were articulated only rarely. Newton's equations were not formulated in any special coordinate system and thus left all directions and all points in space equivalent. They were invariant under rotations and displacements, as we now say. The same applies to his gravitational law. There was little point in emphasizing this fact, and in conjuring up the possibility of laws of nature which show a lower symmetry. As to the conservation laws, the energy law was useful and was instinctively recognized in mechanics even before Galileo.' The momentum and angular momentum con- servation theorems in their full generality were not very useful even though in the special case of central motion they give, of course, one of Kepler's laws. Most books on mechanics, written around the turn of the century and even later, do not mention the general theorem of the conservation of angular momentum.2 It must have been known quite generally because those dealing with the three- body problem, where it is useful, write it down as a matter of course. However, people did not pay very much attention to it. This situation changed radically, as far as the invariance of the equations is concerned, principally as a result of Einstein's theories. Einstein articulated the postulates about the symmetry of space, that is, the equivalence of directions and of different points of space, eloquently.3 He also re-established, in a modified form, the equivalence of coordinate systems in motion and at rest. As far as the conservation laws are concerned, their significance became evident when, as a result of the interest in Bohr's atomic model, the angular momentum conservation theorem became all-important. Having lived in those days, I know that there was universal confidence in that law as well as in the other conservation laws. There was much reason for this confidence because Hamel, as early as 1904, estab- lished the connection between the conservation laws and the fundamental sym- Downloaded by guest on September 28, 2021.