# The infinite universe

With the development of the capabilities of modern astronomy is increasingly a question: Is there the infinite universe? To answer this question, let us take the theory of relativity, where the space and the time are treated as a single entity, the so-called "space - time", in which the time coordinate plays an equally important role that space. Therefore, we can speak only about the finiteness or infinity is united "space - time". But, this is a four-dimensional world with a very special geometric properties, different from the geometric properties of the three-dimensional world in which we live. And infinite or finite four-dimensional "space – time" still says nothing about the spatial infinity of the universe. It should be noted that the four-dimensional "space - time" reflects the well-defined properties, depending on the laws the real universe. A. Friedman showed that separate the question of the spatial and temporal infinity of the universe is not always possible, but only under certain conditions. These conditions are: uniformity, i. e. the uniformity of the distribution of matter in the universe, and isotropic, i. e. the same properties in any direction. Under these conditions a single "space - time" splits into "homogeneous space" and the universal "world time".

The real universe is much more complex homogeneous and isotropic models. This means that the four-dimensional world corresponds to the real world in which we live, and on the "space" and "time" does not split.

Interestingly, some region of space, in fact may be the ultimate in the sense of isolation. Not only Metagalaxy's space, but also any area where there are powerful enough mass, causes severe bending, such as quasar space. But, it does not say anything about the finiteness or infinity of the universe.

The basis of modern ideas about the physical universe is the special theory of relativity. According to this spatial and temporal relationships between real objects around us are not absolute. Their nature entirely depends on the state of motion of the system. In the moving flow of time it slows down the pace and scale of all lengths are reduced. This reduction is stronger, the higher the speed. Are not also the relative finiteness and infinity of the universe?

It turned out, the finite space in the fixed frame of reference, can be infinite with respect to the moving coordinate system. To explain this, let's imagine that we have a very long, but the finiteness straight line, and we measure it by, for example, with help a meter. To an observer in a spaceship carrying at speeds approaching the speed of light, our standard meter will be contracted to a point. Since the points even on the finite straight line is an infinite set, then for an observer in the vehicle the line will be infinitely long. Roughly the same thing happens on the extent of the areas and volumes. Consequently, the finite region of space may become infinite in the moving frame of reference.

In moving systems not only reduces the scale, but also slows down time. Therefore, the finite duration of the existence of an object relative to a fixed coordinate system, may be infinite in a moving coordinate system.

Thus, the finiteness and infinity of the universe and time are relative. In addition, any statement only has the physical sense, when it does not depend on the choice of the coordinate system. In our case, no matter how varied way of describing the physical phenomena the studied content should remain unchanged, that is invariant.

It follows that neither the infinity of the universe in space nor infinity of its in time invariance requirement is not satisfied. Therefore, the question about the infinity of the universe (in space and time) is devoid of physical meaning in the modern sense of infinity.

We should not forget about the infinite variety of the properties of the universe. After all, the universe is primarily a process, the characteristic features of which are continuous and incessant movement of the transitions from one state of matter to another. Therefore, the infinity of the universe is an infinite variety of forms of movement, forms of matter, physical processes, relationships and interactions.