The full development of the point of view outlined in the previous chapter, concerning the transformation between “rest energy” and other forms of energy, implies that we shall eventually have to understand the so-called “elementary” particles as structures arising in relatively invariant patterns of movement occurring at a still lower level than that of these particles. In such structures even the “rest energy” of an elementary particle would be treated as some kind of “inner,” to-and-fro reflecting movement, on a level which is even below that on which nuclear transformations take place.
At present the study of the structure of the “elementary” particles is indeed one of the principal concerns of physical research. A great many clues have been accumulated, which suggest that there does actually exist a new level of the kind mentioned above, in terms of which such structure may perhaps eventually be understood. However, it seems likely that the laws of this level will be as new relative to those of the nucleonic and atomic levels as those of the latter are in relation to the large-scale level. The present situation in elementary particle physics may perhaps be compared with that existing in atomic physics before the time of Niels Bohr, in the sense that a great deal of systematic factual information has been collected, suggesting the need for a fundamentally new set of theoretical concepts, which is, however, yet to be developed. Nevertheless, it is already clear that the “creation” of a particle should correspond to setting up some characteristic relatively invariant kind of movement in a level below that of the elementary particles, with the aid of the necessary quantity of energy, and its “annihilation” to the ending of this pattern of movement, with the liberation of a corresponding quantity of energy. What seems essential here is to set aside the notion of “elementary” particles as the permanent substance of matter, and to regard them as only relatively fixed kinds of entities, which come into being when certain kinds of movement take place, and pass out of being when these kinds of movement cease.
At this point, questions naturally arise. One is: “May we not find new kinds of entities below the level of elementary particles which do in fact constitute the real permanent substance of matter?” Of course, we have no way at present to know what will be discovered in future research on this problem. But it may perhaps be instructive to make a few observations here, which we can carry out on the basis of what we already know. Naturally, these observations will have to be somewhat speculative, but it is hoped that they will serve to help clarify the meaning of this question.
We begin by asking: “Does the assumption of the absolute permanence of entities or substances ever make a real contribution to the laws of physics, or is it not like the Ptolemaic epicycles and the ether theory, in the sense that it is factually not necessary and as far as the theory is concerned, a source of confusion?” To show that this question is well founded, we shall begin by considering everyday life, where as we have seen from our continually changing immediate perceptions, we have been able to abstract certain objects, entities, etc., having more or less constant characteristics, such as shape, size, hardness, and other qualities. Knowing that all these objects can be broken, corroded, melted, burned, or that they are subject to decay, is it not better to refer to them, in effect, as relatively fixed and invariant, rather than as entities with absolutely permanent
Toward a New Theory of Elementary Particles 93
properties? Indeed, if we do this, we can then think of their various movements and transformations, outward and inward, without contradicting the above-described facts, because we have not made the false assumption that since the objects have a fixed name they must always remain essentially the same sorts of things. Thus, it is evident that on the level of ordinary experience, clarity is gained and confusion is decreased if we admit, from the outset, that objects and entities need have only relatively invariant characteristics and that our descriptions of their actions are only approximations, in the sense that all the movements in the atomic, nuclear, and lower levels are (correctly for this level) being ignored. When these movements are taken into account, transformations in which “substances” such as liquids, solids, metals, and gases are created and destroyed can be understood quite simply, as the outcome of “inward” movements on lower levels.
But then when we come to the molecular, atomic, and “elementary” particle levels, we again note a similar process. Thus, an atom, which is a fixed entity on its own level (the very word “atom” means “indivisible” in Greek) is found to be just as capable of fundamental transformations which are the outcome of “inward” movements of its electrons, protons, and neutrons as are the entities on the large-scale level. And, indeed, nowhere have we ever encountered entities which do not have these characteristics.
Can we not then simply refrain from making assumptions concerning the absolute permanence of what is, in the nature of the case, unknown? As can be done in large-scale experience, we can instead regard entities and structures encountered on lower levels as relatively invariant or relatively fixed in their characteristics. In the domain in which these entities or structures are relatively invariant, we may refer to their movements and transformations in a way rather similar to that adopted with regard to the objects of everyday experience. Evidently nothing is lost when we thus replace the notion of absolute permanence by that of relative invariance.
The notion that something is absolutely permanent is moreover evidently one that can never be proved experimentally. For no one can be sure that even if certain things have not changed over a given domain of experience, they will never change, as our domain of experience is broadened (as has indeed actually happened with everything that was ever thought to be absolutely permanent).
It is evident then that by considering entities and structures as relatively invariant, with an as yet unknown domain of invariance, we avoid making unnecessary and unprovable assumptions concerning their absolute invariance. Such a procedure has enormous advantages in research, because one of the main sources of difficulty in the development of new concepts—not only in physics, but also in the whole of science—has been the tendency to hold onto old concepts beyond their domain of validity; this tendency is evidently enchanced by our habit of regarding the entities and structures that we know as absolutely permanent in their characteristics.