According to cosmological theory, the existence of our universe began with a big bang – a rapid expansion of matter from a superficial state to a global scale that continues today.
This happened about 13.7 billion years ago. This is indicated by a number of observed and verified facts. However, this does not explain the question of how the universe began to expand from its original state, that is, before the Big Bang. There is no single answer to this question today, only versions:
Singularity (Friedman). The universe emerged with time during the Big Bang, was in a state of singularity, with infinite density. Time is a means of regulating the sequence of events in the world. If the universe does not exist, then no event occurs and therefore there is no time. In this case, the question of what was before the Big Bang is as absurd as the question of what is written on the edge of a book. Solutions to the equations of the theory of relativity allow solutions in which time is not infinite but has a starting or ending point. Events at these points do not exist here or here.
- Theory of the pulsating world – According to this theory, after some time, the expansion of the universe changes with compression. At this time, under the influence of gravity, all matter is again gathered at one point. There have been speculations that this condition is a precondition for a new big bang that will give rise to a new world. It is possible that the emergence of our world was also preceded by the compression of another world. However, the pulsating world model has encountered serious problems and most specialists do not share it.
- Quantum theory of gravity – Up to 10 ˉ 35 seconds after the big bang, the density of matter was equal to the so-called. Planck density (1093 g / cm3). Under such conditions the quantum effects in the equations of the theory of gravitation become accountable. To date, however, quantum field theory has no established face. It is therefore impossible to say exactly what was happening before 10 ˉ 35 sec and consequently before the big bang.
- Time-space foam (Wheeler, Penrose) – According to some theories, the time-space in the above-mentioned extreme conditions does not look like we are used to. It is a time-space foam in which the so-called foam constantly appears and disappears. “Wormhole” and small autonomous worlds. One of such worlds could, for some reason, take on great dimensions, and it is possible that it represents our world. In such a case, the big bang was preceded by the presence of the universe in a foam state of quantum time-space.
- Theory of Inflation (Guti, Linde, Willenkin) – According to inflation theory, the big bang is the phase transition of a vacuum from a high energy state to a modern, zero-density or near-zero density energy. Part of the energy went to the creation of particles of matter. Before the Big Bang, the high energy of the vacuum forced the universe to explode at great acceleration. According to the theory, this expansion continues even in the most distant parts of the universe, where a phase transition (or big bang) has not yet occurred, although it is impossible to get (or see) there (multiverse) due to the expansion at a huge speed (several times faster than the speed of light).
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