The question of the origin of the Universe, its past and future has worried 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 the title of truth in the last resort, which does not require any additions. Improving technologies have allowed astronomers to make previously unthinkable discoveries, which required a new theoretical base or a significant expansion of existing provisions. One of these phenomena has become dark matter. But first things first.
Cases of bygone days
To understand the term “dark matter” we will return to the beginning of the last century. At that time, the concept of the Universe as a stationary structure dominated. Meanwhile, the general theory of relativity (GR) suggested that sooner or later the force of attraction will lead to the "sticking together" of all objects of space into a single ball, the so-called gravitational collapse will occur. There are no repulsive forces between space objects. Mutual attraction is compensated by centrifugal forces, creating 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 it is actually invented, without obvious reasons.
Expanding universe
The calculations and discoveries of Friedman and Hubble showed that there is no need to violate the harmonious equations of GR using the new constant. It was proved, and today this fact practically does not raise doubts 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 the galaxies over time. It is the measurement of the speed of removal of neighboring space systems from each other that led to the formation of the hypothesis that there is dark matter and dark energy.
Data inconsistent with theory
Fritz Zwicky in 1931, and then Jan Oort in 1932 and in the 1960s, were engaged in counting the mass of galactic matter in a remote cluster and its ratio with the speed of their removal from each other. From time to time, scientists came to the same conclusions: such a quantity of matter is not enough that the gravity created by it can hold together 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 Vera Rubin.
She constructed rotation curves that clearly demonstrate the dependence of the speed of motion of the substance of the galaxy on the distance that separates it from the center of the system. Contrary to theoretical assumptions, it turned out that the velocities of stars with distance from the galactic center do not decrease, but increase. Such behavior of the luminaries could be explained only by the presence of a halo in the galaxy that fills dark matter. Astronomy thus encountered a completely unexplored part of the universe.
Properties and composition
This type of matter is called dark 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 for scientists was to get an answer to the question of what this matter consists of. Astrophysicists tried to “fill” it with the usual baryonic matter (baryonic matter consists of more or less studied protons, neutrons and electrons). The dark halo of galaxies included compact low-emitting stars such as brown dwarfs and huge planets in mass close to Jupiter. However, such assumptions did not pass the test. Thus, baryonic matter, familiar and known, 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 microworld, according to which for each known particle there is a supersymmetric pair. So they make up dark matter. However, evidence for the existence of such particles has not 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 with the surprises that the Universe had prepared for scientists. In 1998, astrophysicists had another chance to compare these theories with facts. This year was marked by a supernova explosion in a galaxy far from us.
Astronomers measured the distance to it and were extremely surprised by the data: the star flared 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 higher than it was 14 billion years ago, when a big explosion was supposedly happened.
As you know, in order to accelerate the movement of the body, it needs to transfer energy. The force that forces the universe to expand faster has been called dark energy. This is no less mysterious part of the cosmos than dark matter. It is only known that it is characterized by a uniform distribution throughout the Universe, and its effect can be recorded only at vast cosmic distances.
And again the cosmological constant
Dark energy shook 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 Einstein’s forgotten cosmological constant, which again from the category of a large scientific error can turn into the number of working hypotheses. Its presence in the equations creates antigravity, leading to accelerated expansion. However, some consequences of the cosmological constant are not consistent with the observational data.
Today, dark matter and dark energy, which make up most of the matter in the Universe, are puzzles for scientists. There is no single answer to the question about their nature. Moreover, perhaps this is not the last secret that keeps space from us. Dark matter and energy may be the threshold of new discoveries that can revolutionize our understanding of the structure of the universe.