PACS number(s): 95.75.Wx
Today all the more attention is paid to the studies of the questions connected to manifestation of space-time different characteristics. Whatever area of physics we take, in the end they are all about physics of space and Time. Wheeler J.  noted that eventually, all physics will be expressed through terms of space and time. Such standpoint keep so Reichenbach H.  .
Penetrating in structural manifold of space-time, we allocate each of them with determined dimensions. So, the space has three dimensions. Time has one. As a whole, the World is represented to us by Minkowski as a unified 4-dimension space. Here comes the question: ”Does it show us a real picture?” Wheeler J.  indicates in this respect: ”Is dimensionality 3 plus 1 of space-time exact or only drawn near by description to reality ?”
Modeling the different variants of the World’s structure, we analyze it only by increasing of the number of the space dimensions and we accept, that n > 3 (where n - is a number of the spatial co-ordinates), but we see Time as 1-measured part of the high space that can be observed in particular in works where development of the theory of supersymmetry and supergravitation examined and also in the other researches concerning problems of the
Speaking in 1908 at the 80 th Assembly of German Scientists and Physicians (Köln) Minkowski  in the report ”Space and Time” said, that his point of view at space and time have appeared on experimentally-physical base. Space and time from now and than is dimensions transformed into fictions and only some kind of their combination must remain as independent. Here I would like to say a couple of words on cause of the Minkowski´s statement. From the most modern general physical concepts we can see clearly that when Time and space were integrated into space-time it was necessary to make a comment that both Time and space itself inside of this category can a p r i o r i have certain own physical characteristics. Even though Time and space are integrated into four dimensional space, however, these are quite different physical concepts and as will be shown below, Time is not a space and space is not Time.
It is possible to show on a simple model that above mentioned natural objects are not the same. But first we have to make the necessary note on two fundamental properties, which Time has.
At first: in modern physics this characteristic is identified differently as a current, a beam, a course , an axis, an arrow .
At second: Time is submitted to the law of irreversibility, but for space equivalent law does not exist.
We shall consider the simple mental experiment. Let us have some element of the volume of the space which is insulated from all of the possible external influences. We shall connect it with the comparable element of Time. Due to the absences of active external influences the given volume of analyzed space can remain static, so will be in balance and rest. This state can be observed for infinitely long period as far as the restrictions entered above are valid. Let us take a look now how Time behaves in the given situation. Taken in consideration how the physical processes generally course, we can say that irrespectively of existence or nonexistence of external influences Time for our area of space does not stop its running, so transition from the Past to the Future through the Present goes strictly within the framework of the causality-effect law. Thus, we can say that Time and space are two absolutely different physical categories.
In a part of the Universe which we observe today ( < 1028 cm ) it is difficult to find and specify the real physical processes which would guarantee hard restrictions on a course of Time and course strong breaks of chronology and causality of events.
If we look close at the General Relativity we can see certain disproportion considering an importance of an influence of gravitation on space and Time. This fact has been mentioned by De Witt : “ Time is key element. It appears, that even though the space is twisted in a gravitation field, curvature of time is much more important”.
Let us move now to that experimental and theoretical observations and conclusions, which well known today in physics and which directly characterize Time as a physical environment.
1. In order to emphasize physical difference between Time and space, it is said that they have the different signature. It is reflected in different signs before members of the left part of equality below :
X2 + Y2 + Z2 – C2T2 = 0,
where X, Y, Z – three valid coordinates, C – velocity of the light, T – coordinate of time.
2. Today Time is used basically as a chronological scale. It appears as determined system with strict causal and chronological connections. In other words, there is consecutive alternation of the Past, Present and Future. Let us look closer at these three concepts. These elements are strictly chronological parameters and they are functionally connected only to Time. That make us assume Time has the only time row , associative members of which are Future, Present and Past.
3. One of the most important established facts is effect of the deceleration of Time that has been discovered by A. Einstein  in Special and General Relativity. I have to note that Special and General Relativity represent theories of quantitative (metric) properties of Time. But Time has also other, so called qualitative (or topological), characteristics.
4. The space-time is orientated in Time, so there are two classes of vectors, one of which is directed to the Future and another to the Past. There is also the arrow of the Time precisely given by a direction of growth of the quasi insulated thermodynamic system’s entropy .
5. It is revealed that in row of the processes of the disintegration on the elementary particle’s level, for example long-living neutral K-meson (KoL) infringement of T - invariable (combined inversion CP) take place . Here I would like to say a couple of words about the importance of the factor of Time in process of the disintegration in general. The role of Time most effectively appears as a powerful physical factor in reactions of the decomposition of the different material bodies. Here we talk of course about those processes which are not directly connected to the evident external power influence. Here process of decomposition of the objects correlates only with their internal condition. In fact sometimes the system which appears to be steady in space disintegrates without visible external reasons in a certain long, but anyway final, time interval. Certainly, that cost by real natural powers. Obviously the main physical source of breaking balance in such systems might be Time itself. Most physically motivated examples of the influence of Time on the natural systems can be a following events:
- disintegration of a proton p (tp ~ 3 · 1033 yrs) certainly without taking into account effect Rubakov (induced by the magnetic monopole of disintegration of a proton);
- explosions of supernova & nova stars;
- gravitational instability of a matter in scales of the Universe and etc.
6. Considering the presence of antimatter which is not yet discovered in the Universe in large amounts, we can say that there is a difference in direction of the course of Time in a matter and an antimatter. Indeed, material bodies are characterized by positive direction of Time - such direction of Time in which the majority of thermodynamic processes in insulated systems take
place. And for an antimatter considering the mechanism of inversion (t → – t) the direction of the course of Time becomes opposite .
7. In real macro physical process running in the Universe entry conditions are set by the basis founding on irreversibility of Time of the real World .
8. M. Planck has discovered that Time has the least duration. This value is estimated as tp ~ 10 – 43 sec , .
9. In the quantum mechanics there is a known correlation of uncertainty of Heisinberg which allow us to install relation between energy and Time ,
∆E ∆t ≥ h
where h – the Plank’s constant. This formula has a deep physical sense since it gives us possibility to value, in the first approximations at least, the physical relation between Time and energy.
10. The most exact determined characteristics of Time are: i s o s t r o p o i  and homogeneous , which contains (due to freedom of a choice of counting of Time’s beginning) the law of the conservation of energy which is corresponded to the homogeneous current of Time.
11. As we know from astrophysics, the Hubble’s constant H depends on Time t thus
H = f ( t ) , (c – 1)
12. Theoretical researches in area of relativistic cosmology show, that curvature of the space a of the Universe is the function the Time’s factor :
a = f ( t )
It’s possible to give more examples, but I think that above mentioned facts are enough.
Obviously that on the basis of these facts it is possible to conclude that today is already impossible to speak about Time simply as one of philosophical categories because now the physics operates with serious facts which speak for the benefit of the idea that Time is a physical environment which actively participates in Universe and occupies one of the most main positions in hierarchy of the Nature.
In summary, I would like to note that the problem of a construction of Time  in the past occupied minds of ancient scientists. And now the research of physical essence of Time attracts big attention. There is a significant number of hypothesizes on a physical nature of Time which are reflected for example in works [18 - 30].
1. Wheeler J., Astrofisica E Cosmologia, Gravitazione, Quanti E Relatività, Givnti Barbèra, Firenzo, 1979.
2. Reichenbach H., The direction of Time, Berkeley, Los Angeles, 1956, 280 + XII p.
3. Minkowski H7, Space and Time, address delivered at the 80 th Assembly of German Scientists and Physicians, Köln, 1908.
4. Kozyrev N. A., On the possibility of experimental investigation of the properties of time // Time in Science and Philosophy, Prague, 1971, p. I 11-132.
5. Hawking S., Ellis G., The Large Scale Structure of Space-Time, Cambridge Univ. Press., 1973.
6. De Witt B., Scientific American, 2 , 50, 1984.
7. Einstein A., Preuss. Akad. Wiss., Berlin Sitzber, 778, 779, 831, 834, (1915).
8. Whitrow G., The Natural Philosophy of Time, Edinburgh, 1961, 324 + XI p.
9. Mukhin I. A., Experimental Nuclear Physics, v. 2 // Physics Elementary Particles, M., Atompublishers, 1974.
10.Korotaev S. M., The Earth & the Universe, 2, 53, 1989.
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15. Treder H.-J., Einstein-Centernarium, Akad.-Verlag, Berlin, 1979.
16. Lang K., Astrophysical Formulae, Springer-Verlag, Berlin, NY, 1974.
17. Landau L.D., Lifshic E. M., Theory of Field, v. &, M., Science,1973.
18. Chernin A. D., Physics of Time, M., Science, 1987.
19. Gold T., The Nature of Time, Cornell Univ. Press., Ithaca, 1967.
20. Zlobin I., Engineer, 7, 31, 1991.
21. Hoyle F., Narlikar J., Time-symmetric electrodynamics and the arrow of time in cosmology, Proc. Soc., London, A 227, 1-23, 1963.
22. Saharov I. D., JETP, v. 87, 375, 1984.
23. Novikov I. D., Libsher D. E., Nature, 4, 14, 1985.
24. Askin J. F., The Problem of Time., IDEA, V., 1966.
25. Study of Time, I, Proc. 1th Conference of the International Society for the Study of Time, NY, 1972.
26. Study of Time, II, Proc. 2th Conference of the International Society for the Study of Time, NY, 1975.
27. Study of Time, III, Proc. 3th Conference of the International Society for the Study of Time, NY, 1978.
28. Study of Time, IV, Proc. 4th Conference of the International Society for the Study of Time, NY, 1981.
29. On the Way to Understanding the Time Phenomenon the Construction of Time in Natural Science, Part 1 // Interdisciplinary Time Studies, World Scientific, 1995.
30. On the Way to Understanding the Time Phenomenon the Construction of Time in Natural Science, Part 2 // “Active” Properties of Time According to N. A. Kozyrev, World Scientific, 1996.