The Nature of Time: Geometry, Physics and Perception. Edited by Rosolino Buccheri, Metod Saniga, and William Mark Stuckey. Kluwer Academic Publishers: Dordrecht / Boston / London (published in cooperation with NATO Scientific Affairs Division), pp. 427-435.
© A.P.Levich

PARADIGMS OF NATURAL SCIENCE AND SUBSTANTIAL

TEMPOROLOGY

One can formulate some implicit premises which dominate in the present natural science:

• Studies of time are performed by philosophy rather than by natural science.
• Time in science is an initial, undefinable concept.
• To measure time, it is sufficient to have physical clocks on the basis of gravitational or electromagnetic processes.
• The problems of time in natural science are the solved or unsolved problems of relativity theory.
• Our Universe is an isolated system.
• The conceptual armoury of science has no place for substances like phlogiston, light-bearing ether, entelecheia, etc.

During the 20th century there appeared some tendencies in natural science which lead to an alteration of the existing scientific paradigm [14]. It often happened in the history of science that the most difficult problems of natural science required a revision of the time concept for their solution. This is demonstrated, in particular, by the works of L. Boltzmann, A. Einstein, N. Kozyrev. Ludwig Boltzmann's [4] studies of the contradiction between the time reversibility of the equations of mechanical motion and the irreversibility of the equations of statistical physics have led to the statement of a question: "Is the time reversible"? Albert Einstein [7] was able to reach an agreement between the velocity addition law in classical mechanics and the light propagation phenomena by refining the operational procedure of establishing simultaneity between remote events; in doing so, he introduced a new type of clocks, "light clocks", or Langevin clocks. Astronomer Nikolai Kozyrev [21, 9], investigating the problem of origin of stellar energy, arrived at the hypothesis of the existence of a new physical essence, which does not coincide with matter, or field, or space in their usual understanding. He named this essence "the time flow".

It became clear by the second half of the last century that scientists deal with times rather than time. In my view, one of the significant reasons of the increased attention of the specialists to the temporal aspects of their specific areas is the comprehension of the fact that there can be different clocks that measure the variability of objects. Clocks are not only physical processes on the basis of gravitational forces or the electromagnetic radiation of atoms. There are biological clocks: the processes of breath, cell fission, growth of organisms, exchange of generations or species... There are geological annals, the processes occurring in psychology, society, history... The main property in which the possible types of clocks can differ is the uniformity of their course [12]. More rigorously, the time intervals which turn out to be equal when measured by one type of clocks, become different when using other clocks. The conventional nature of the choice of clocks has been understood long ago by the methodologists of science [22, 19], but only in the recent decades the natural scientists have comprehended the importance of such a convention. A natural motivation for using nonphysical methods of measuring time when studying objects of nonphysical nature was a hope to discover the laws of their variability, or their "equations of motion". The construction of dynamical equations describing natural systems remains one of the basic tasks of scientific research. Generalized motion of systems, looking complicated and involved when described with the aid of physical clocks, can become simple and natural when described using specific time units, adequate to the nature of the system itself.

One more tendency of the present natural science, washing out the existing paradigm, is the rebirth of the substantial outlook. A wide circle of substantial ideas employs the active properties of physical vacuum: there multiplies the set of scalar, vector and tensor fields, suggested in order to explain the phenomena of cosmology, particle theory, biology, psychology, communications. They claimed to exist ontologically. The above-mentioned Kozyrev's conception is in essence substantial. Prigogine, solving the time irreversibility problem, introduces additional terms into the equations of general relativity which describe "creation of matter from space-time" in the form of particles with the Planck value of mass [23]. I would like to note that the substantial conceptions mentioned here and many others tend to the notion of an open rather than isolated World with respect to matter or energy. The revival of the substantial outlook is a kind of response to a long-term predominance of the relational paradigms. However, as a rule, one does not return, for instance, to the elastic light-bearing ether of the 19th century. The question is a search for understanding the physical structure of space and fields. There exist substantial approaches to the nature of time along with relational ones (see, e.g., [2, 3]). These approaches are not confronted with each other but are rather complementary.

There is an obstacle on the way of including the problems of time into the problems of natural science as such, and this obstacle is more and more clearly realized. Time in modern science is an initial and undefinable concept. Therefore a basic task of both time researchers and disciplinary specialists is to create an explicit construction of time, or its model. In other words, it is necessary to replace time in the initial conceptual basis by other basic postulates. After such a replacement it will be possible to formulate the properties of time itself in the form of theorems of a deductive theory instead of axioms. It becomes possible to discuss any properties of time only in the framework of its certain model (see, e.g., [2, 6, 18, 24, 25]).

Creation of a construction of time actually leads to reworking of the whole substructure of the conceptual means. It is quite clear that such reworking inevitably affects a wide circle of basic concepts of natural science. Among such concepts are space, motion, matter, energy, interaction, charges, entropy, life... One thus cannot speak of a specific study, but rather of a vast and deep research programme [5], and its implementation may require the effort of several generations of researchers. At present, however, the main point in this problem is to understand that it does exist. A number of centuries have been necessary for that.

Now, at the beginning of the new century, certain features of a new scientific paradigm are becoming visible. Its comprehension may be able to help both temporology and natural science as a whole in their development:

• One can speak of natural references of the time concept. The time phenomenon may become an object of natural science at full rights.
• The time of natural systems has a structure and can be an object of modelling.
• The reference processes used to measure the variability of an object, i.e., clock, can be of quite various nature. Different clock can lack simultaneous uniformity, and the descriptions of the laws of motion obtained with their aid may be irreducible to each other by simple transformations.
• Further development of the concepts of space, time, matter, motion and interaction in the conceptual basis of natural science probably needs some new essences whose emergence is most probable in the framework of the substantial approaches.
• A radical solution of the problems of the course and irreversibility of time probably requires that the existence of isolated system should be rejected. It thus leads to the notion of an open, nonlinear, self-organized World, possibly becoming more and more complicated.

The purpose of my further presentation is to suggest an example of a substantial construction of time. My main reason for studying time is a hope to find the ways of derivation rather than guessing the laws that govern the variability of the World objects, or in other words, derivation of the fundamental equations of generalized motion.

The dynamical theories in science necessarily include a number of components, whose development, deliberately or more often implicitly, forms stages in the creation of theories [11]:

O-component: choice and description of an idealized structure of the elementary objects of the theory.

S-component: description of the set of admissible states of the objects, called the space of states of the theory.

C-component: description of the ways of object variability.

T-component: mapping of the object variation process into variation of the chosen reference (clock).

L-component: formulation of the law of object variability, which elicit their real motion in the space of states. The variability law has, as a rule, the form of an equation of generalized motion of the theory.

I-component: the use of a set of interpretation procedures which put into correspondence the formal concepts of the theory to specific objects of the actual research area, and the latter to quantities measured in the experiment.

I would like to pay special attention to the stages of the choice of elementary objects, the space of states and the ways of variability in the theory. Newell and Simon [20] have named these stages the qualitative structure principles of the theory. Here are some examples of such principles: the atomistic doctrine; material points in the phase space of positions and velocities in classical mechanics; probability amplitudes in the infinite-dimensional Hilbert space of quantum mechanics; the structure of an atom and an atomic nucleus; the geo- or heliocentric system of the near space; Everitt's parallel Universes; the cellular theory of organisms; the bacterial nature of infectious diseases; the population, trophic and other structures of the Earth's ecosystem and biosphere; plate tectonics in geology; the class theory of the society.

In the present work I propose to discuss the structure principles of substantial temporology and the approaches to variability parametrization, i.e., to the choice of clock.

Now I would like to present the postulates of the metabolic approach to the description of the substantial nature of time [12, 13]:

• All natural systems are hierarchic.
• At each level of the hierarchic structure of a system there occurs compulsory substitution of its elements - the master process.
• At the depth levels of the system structure there exist flows which are external with respect to the system and which generate the master process. All systems are open with respect to generating flows. In particular, our Universe turns out to be an open system.
• The substance of the generating flows is not a substrate represented by fermionic particles, atoms, molecules or other complexes of particles possessing charges and taking part in interactions. The charges responsible for the interaction of objects are sources or sinks of generating flows in our World. (A clear image of the charges is a spring, a fountain or a jet, "spouting" in the substantial "reservoir".) The dynamic characteristics of the generating flows in sources and sinks form the properties of particles - charges and the mechanism of their interaction. Thus the substance of the generating flows is not "heavy" matter, but creates this matter. The substance does not take part in the interactions known by now, but provides a realization of these interactions. In other words, the material nature and the interacting ability have a different status of being for generating flows as compared with "heavy" matter.
• The whole set of elements of generating flows forms space, or the environment of the system.
• The motion of a system in its space (metabolic motion) is carried out not by "moving apart" the ambient elements, but by their replacement in the system, namely, by "entering" some "points" of space into the system while others are "leaving" it. (A clear image of metabolic motion is the movement of an image on the screen of a kinescope, or of symbols in a "running line" advertisement.)
• The generating flow "entry" into the system may be identified with the course of time in the system, i.e., the generating flows are natural references of time.

Let us briefly formulate some consequences of the metabolic approach.

• The time phenomenon in our World is a consequence of the openness of the Universe and all its subsystems with respect to substantial generating flows.
• The becoming phenomenon can be described and parametrized by storage or decrease of the generating flow substance in the system.
• Metabolic motion is a special case of the course of time; both consist in substitution of environmental substance in the system.
• The notion of a generating flow unifies the following concepts: particles of "heavy" matter as singularities of the flow; space as a substantial medium; time and motion as processes of element substitution in the systems; particle interactions as manifestations of dynamical characteristics of the flow.
• Different "generations" of elements of the generating flow substance form a set of neighbourhoods of particles which are sources of space, thus creating the notion of "vicinity" of its points, its topology and metric.
• The substance of generating flows is, on the one hand, omnipresent and omni-penetrating in our World, but, on the other, it does not interact in a usual way with "heavy" matter and is therefore invisible for usual instruments.
• Since the generating flow substance does not take part in the usual interactions and, while "penetrating through" objects, does not cause such usual effects for motion in a medium as friction and resistance, it is not the ether of the 19th century. In the conceptual basis of natural science, the notions closest to this substance are the field or physical vacuum.
• The generating flows belonging to different levels of matter structure create in a unified way different charges, interactions, spaces and times, maybe irreducible to each other. Along with the charges of physical interactions, one may consider living organisms and the phenomenon of psyche as specific charges.
• The time created by the generating flows turns out to be reversible or irreversible to the same extent and in the same sense as are reversible or irreversible the flows themselves.

I call the measurement of variability, i.e., mapping of an alteration process into a numerical set, "parametrization of time". In the framework of the metabolic approach, the variability is formalized by element substitutions in a system on different levels of its hierarchic structure. It is suggested to measure the variability of the master process by counting the number of replaced elements of the system. We thus introduce the following definitions [12]:

Clock: a reference object belonging to a certain level of the system structure.

Imperativity principle: changes in the set of elements of the reference object by one element are regarded to be equal and may be appointed a unit of time.

Metabolic clock: a natural object whose element replacement is chosen as a uniform variability reference.

Event (time instant): the event of element replacement in the system.

Metabolic time interval: the number of elements replaced in the system between two events.

One can discuss the properties of metabolic time in the framework of the suggested model:

• Since the systems under consideration are hierarchic, and the master process takes place at each level of the system structure, metabolic time turns out to be multicomponent: each level of the system structure possesses metabolic time of its own.
• Since the clocks whose variability is taken as a reference belong to one of the levels of the system, element replacements on other levels may turn out to be non-uniform relative to this reference variability.
• Since the time reference is delegated by a specific hierarchic level of a specific system, the measured time is not universal: it is system-specific and even level-specific.
• If an object from a certain level of natural hierarchy is chosen as a time reference, then the events (element replacements) occurring on deeper levels of the hierarchy turn out to be out of time, or "instantaneous".

The quantitative aspect of the metabolic approach consists in counting the number of elements in sets that form the system. The comparison procedure between sets (both finite and infinite) by the number of elements is correctly elaborated for structureless sets. However, the whole theoretical natural science is built on the basis of modelling objects by some mathematical structures (sets with relations, algebraic constructions, topological spaces, etc.). In particular, systems created by several generating flows cannot be presented as hierarchies of structureless sets. Therefore a nontrivial application of the metabolic approach requires the ability to compare sets possessing structure. This ability must replace the method of comparing structureless sets by numbers of elements.

Since every admissible morphism transforms the system to a new state without changing its general structure, the number of structure-preserving morphisms can be interpreted as the number of "micro-states" of the system preserving its "macro-state", i.e., its general structure. Such an interpretation makes it possible to call the logarithm of the specific number of transformations of the system state its generalized entropy.

The above entropy parametrization of metabolic time allows one to approach a derivation of the variability law in systems theory. This derivation rests on postulating an extremality principle which determines a "trajectory" of the system in its space of states: from a given state, the system transforms to a state with the "strongest" structure admitted by the available resources. The above functor method of structure comparison makes it possible to give an entropy formulation of the extremal principle: from a given state, the system transforms to a state with the greatest generalized entropy admitted by the available resources.

The entropy extremal principle, along with the ability to derive rather than guess the form of the functional to be extremized, generalizes the formalism of Janes [8] and makes it possible to formulate variational problems. Variational modelling, being applied to the description of open systems, leads to useful theorems in systems theory and enables one to find new interpretations of the extremal principle [16, 1, 15]. The solutions of variational problems either directly describe the dynamics of systems in metabolic time [15] or create the Euler-Lagrange equations of motion.

This work is supported by Russian Humanitarian Foundation (grant No 00-03-00360a).