# About the Universe

As you know, all the distant galaxies of the **Universe** "run away" from us at a rate directly proportional to the distance to them (Hubble's law). At a distance of about 5000 megaparsec (1,5*10^{28} cm), the escape velocity of galaxies in the universe reaches the speed of light. This means that light from such a distance will never be able to reach us, and this distance is called "the light horizon of the universe". The volume of the visible universe is 15*10^{84} cm^{3}, and if the density of matter in the universe corresponds to a critical density of about 10^{-29} g/cm^{3}, then the total mass of the universe will be 15*10^{55} g. In this case, the gravitational radius for a given mass will coincide in magnitude with the horizon of the Universe, it will turn out to be a closed hole, that is, a black hole for External observer.

One point of view, whether the universe is really infinite or finite in space and volume, does not exist. Nevertheless, the observed universe is finite, since the speed of light is finite and there was a Big Bang. If the Universe is really spatially limited, then in some of its models, moving in a straight line in any direction, one can get to the starting point of the journey.

The question of the form of the universe is an important open question of cosmology. Mathematically speaking, there is the problem of searching for the three-dimensional topology of the spatial cross-section of the universe. The general theory of relativity as a local theory can not give a complete answer to this question. In addition, it is not known whether the universe is globally spatially flat, that is, whether the laws of Euclidean geometry are applicable on the largest scales. At present, most cosmologists believe that the observable universe is very close to spatially flat, where massive objects distort space-time.

There are assumptions that the universe was originally born rotating. The classical idea of the origin is the idea of the isotropy of the Big Bang, that is, the spread of energy equally in all directions. However, a competing hypothesis emerged and gained some confirmation: it is established that spiral arms of galaxies twisted counterclockwise are found to be 7% more frequent than galaxies with "opposite orientation", which may indicate the presence of the original moment of rotation of the Universe.