There are a lot of theories and hypotheses about the origin of the Universe, they are all different and all as one answer the question: "Where did the Universe come from?" The most interesting thing is that, considering one theory, analyzing it, you become its supporter until you move on to the study of another theory, which, in turn, convinces itself of its own rightness - and so on and on. Probably, people will not soon be able to find the right answer to the question of where the universe came from.
If we take the most ancient theory of the origin of the Universe, then, in accordance with the undeniable source for many - the Bible - the world was created by the Creator in about 5508 BC. This theological hypothesis of the origin of the world is well known, but it is mainly adhered to by members of the clergy and especially religious people. Scientists who question everything and everything, including the existence of God, naturally have a different idea about the origin of the world.
If you look into the explanatory dictionary, then the Universe is a system of the universe, which includes all cosmic space and the celestial bodies that are in it. An alternative definition of the universe is "a cluster of stars and galaxies."
The most common scientific hypothesis explaining where the universe came from is considered to be the Big Bang theory.
In accordance with it, approximately 20 billion years ago, the entire Universe substituted a very small substance, the size of which was less than a grain of sand. However, despite its tiny size, the density of this substance was enormous: approximately 1100 g / cm3. Of course, in the material there were no stars, no planets, no galaxies to which we were accustomed, but it itself represented a certain germ that could potentially create all this variety of celestial bodies. This substance can be compared with a small seed, from which a powerful and branchy tree subsequently grows.
It was because of the high density of the original substance that an explosion occurred that divided this smallest particle into billions of smaller particles - of which the Universe subsequently arose.
There is another hypothesis about the big bang that answers the question of where the universe came from. In principle, the essence of these two theories is almost identical, except that in this hypothesis a physical vacuum appears instead of the substance from which the Universe emerged. That is, the whole world was due to an explosion in a vacuum environment.
Vacuum in Latin means “void”, but the meaning of this concept is much wider: vacuum is not a void in the generally accepted sense of the word, but a state in which all that exists is hidden and potentially contained. Vacuum has the ability to change its structure - just like water turns into ice or steam. In the process of changing this structure, an explosion occurred that entailed the emergence of the Universe.
In addition to theological and scientific hypotheses explaining where the universe came from, there is a scientific and philosophical point of view on this problem. She is considering the fundamental possibility of creating the Universe with a certain higher rational Principle. Such a theory implies that the world did not always exist: it has its own starting point, and even more so - the whole Universe is constantly evolving and growing.
This is the conclusion made by scientists studying the composition and radiance of stars. So, in the 30s of the twentieth century, when studying the Milky Way, it was found that the light emitted by the stars is shifted to the red region of the spectrum. The farther the distance from us to the star, the more this displacement is more pronounced. It was this observation that gave scientists information that the Universe is constantly expanding.
The second scientific fact that confirmed the development of the Universe was the "death" of stars. Based on the chemical composition of the star, its body consists of hydrogen, which is constantly involved in various reactions, turning into heavier elements. When hydrogen is depleted, the star "dies." According to some theories, all the planets of our system can be the result of the "death" of stars.
This discovery provided the basis for another conclusion: since the decay of hydrogen is a natural and irreversible process, the Universe naturally and gradually moves to its end.