The question of the origin of the Universe, its past and future has been worrying people since time immemorial. For many centuries, theories have arisen and refuted, offering a picture of the world based on known data. A fundamental shock to the scientific world was Einstein's theory of relativity. She also made a huge contribution to understanding the processes that form the Universe. However, the theory of relativity could not claim to be the ultimate truth, which does not require any additions. Improving technologies allowed astronomers to make previously unthinkable discoveries that required a new theoretical base or a significant expansion of existing provisions. One such phenomenon is dark matter. But first things first.
Cases of bygone days
To understand the term "dark matter" let's go back to the beginning of the last century. At that time, the idea of the Universe as a stationary structure dominated. Meanwhile, the general theory of relativity (GR) assumed that sooner or later the force of attraction would lead to the "sticking" of all space objects into a single ball, it would happen like thiscalled gravitational collapse. There are no repulsive forces between space objects. Mutual attraction is compensated by centrifugal forces that create a constant movement of stars, planets and other bodies. In this way, the balance of the system is maintained.
In order to prevent the theoretical collapse of the Universe, Einstein introduced a cosmological constant - a value that brings the system to the necessary stationary state, but at the same time is actually invented, having no obvious grounds.
Expanding Universe
The calculations and discoveries of Friedman and Hubble showed that there is no need to violate the harmonious equations of general relativity with the help of a new constant. It has been proven, and today this fact is practically beyond doubt, that the Universe is expanding, it once had a beginning, and there can be no talk of stationarity. Further development of cosmology led to the emergence of the big bang theory. The main confirmation of the new assumptions is the observed increase in the distance between galaxies with time. It was the measurement of the speed of removal from each other of neighboring space systems that led to the formation of the hypothesis that there is dark matter and dark energy.
Data not consistent with theory
Fritz Zwicky in 1931, and then Jan Oort in 1932 and in the 1960s, counted the mass of matter of galaxies in a distant cluster and its ratio with the speed of their removal from each other. From time to time, scientists came to the same conclusions: this amount of matter is not enough for the gravity created by it to be able to holdtogether galaxies moving at such high speeds. Zwicky and Oort suggested that there is a hidden mass, the dark matter of the Universe, which does not allow space objects to scatter in different directions.
However, the hypothesis was recognized by the scientific world only in the seventies, after the announcement of the results of the work of Vera Rubin.
She built rotation curves that clearly demonstrate the dependence of the speed of movement of the matter of the galaxy on the distance that separates it from the center of the system. Contrary to theoretical assumptions, it turned out that the speeds of stars do not decrease as they move away from the galactic center, but increase. Such behavior of the luminaries could be explained only by the presence of a halo in the galaxy, which is filled with dark matter. Astronomy, thus, faced with a completely unexplored part of the universe.
Properties and composition
Dark this kind of matter is called because it cannot be seen by any existing means. Its presence is recognized by an indirect sign: dark matter creates a gravitational field, while not emitting completely electromagnetic waves.
The most important task that arose before scientists was to get an answer to the question of what this matter consists of. Astrophysicists tried to "fill" it with the usual baryon matter (baryon matter consists of more or less studied protons, neutrons and electrons). The dark halo of galaxies included compact, weakly radiating stars of the typebrown dwarfs and huge planets close to Jupiter in mass. However, these assumptions have not stood up to scrutiny. Baryon matter, familiar and known, thus cannot play a significant role in the hidden mass of galaxies.
Today, physics is looking for unknown components. The practical research of scientists is based on the theory of supersymmetry of the microcosm, according to which for each known particle there is a supersymmetric pair. These are the ones that make up dark matter. However, no evidence of the existence of such particles has yet been obtained, perhaps this is a matter for the near future.
Dark energy
The discovery of a new type of matter did not end the surprises prepared by the Universe for scientists. In 1998, astrophysicists had another chance to compare the data of theories with the facts. This year was marked by the explosion of a supernova in a galaxy far from us.
Astronomers measured the distance to it and were extremely surprised by the data obtained: the star flared up much further than it should have been according to the existing theory. It turned out that the rate of expansion of the universe increases with time: now it is much faster than it was 14 billion years ago, when the big bang supposedly happened.
As you know, in order to accelerate the movement of the body, it needs to transfer energy. The force that causes the universe to expand faster has become known as dark energy. This is no less mysterious part of the cosmos than dark matter. It is known only that it is characteristicuniform distribution throughout the universe, and its impact can be registered only at huge cosmic distances.
And again the cosmological constant
Dark energy has shaken the big bang theory. Part of the scientific world is skeptical about the possibility of such a substance and the acceleration of expansion caused by it. Some astrophysicists are trying to revive the forgotten Einstein's cosmological constant, which again from the category of a big scientific mistake can go into the number of working hypotheses. Its presence in the equations creates anti-gravity, leading to an acceleration of expansion. However, some of the consequences of the presence of the cosmological constant do not agree with the observational data.
Today, dark matter and dark energy, which make up most of the matter in the universe, are mysteries for scientists. There is no single answer to the question about their nature. Moreover, perhaps this is not the last secret that space keeps from us. Dark matter and energy may become the threshold of new discoveries that can turn our understanding of the structure of the Universe.
