Cosmology, the science of the properties and evolution of the Universe, originated in ancient times. Over the past hundred years, this
The authors divided the history of the development of cosmology into four stages.
Cosmology, beginning: 1917-1960
In the first period of the development of mathematical cosmology, many new fundamental ideas appeared, which still play an important role in the formation of theoretical cosmology. Here is some of them:
- Cosmological constant and vacuum energy;
- Uniformity of the Universe;
- Inhomogeneous anisotropic cosmological models;
- Evolution versus the steady state of the universe;
- Hot Big Bang;
- Causality and time travel;
- Local and global structure.
All the ideas presented above are the same.fundamental and important in the study of theoretical cosmology today, as at the dawn of the development of science. As the authors of the article note, the subsequent development of the field in the coming decades has proven that all these new and important ideas “still play a large role, but, at the same time, only a small part of the complex network of methods and directions that make up mathematical cosmology today.”
dateFebruary 8, 1917considered the birth of modern cosmology.It was then that Einstein demonstrated the first application of the General Theory of Relativity (GR) to the Universe. He created the first modern cosmological model in which matter is motionless. At the same time, it has a finite volume, it has no boundaries. The static nature of the Universe according to Einstein is achieved due tocosmological constant. That's what it means.
Dark energy counteracts gravity“responsible” for the expansion of space. Unlike ordinary gravity, which occurs around large masses, dark energy acts everywhere, so it is associated with space itself. Scientists even calculated how much of this “repulsion energy” is contained in a cubic meter of space: 6×10−10 Joules per cubic meter. The cosmological constant is the magnitude of that very force. This is the energy of space-time itself. Its magnitude at any point in the Universe does not change with time.
Then, a breakthrough in modern cosmology was made by Russian mathematician Alexander Friedman. IN1922he found the solution to Einstein's equations, whichdescribe a dynamically expanding Universe. In addition, the theory was experimentally confirmed. British astronomer Edwin Hubble succeeded in this. IN1929from discovered the famousredshiftgalaxies.
Redshift—expansion indicatorUniverse. When space expands, galaxies “fly away” from each other, but their coordinates remain the same. The easiest way to understand this process is to imagine that space is a balloon on which galaxies are “glued.” It (like space) is expanding, but the position of the galaxies does not change, the marks are “glued” to their coordinates.
Later,in 1947, based on this information, Georgy Gamow (USA) formulatedhot universe theory. According to this cosmological model, its evolution began from a state of dense hot plasma. The universe consisted of elementary particles.
Two years later,in 1949 , this process of the birth of the Universe became known asBig explosion. The term is believed to have been coinedBritish astronomer Fred Hoyle. According to this model, before the Universe began to expand, it was in a singular state. Today, these two concepts are combined, but in fact they are independent.
Second period: 1960–1980
New ideas that arose during this period and have a special relationship to cosmology can be summarized as follows:
- Geometric extensions of General Relativity;
- Singularity theorems, global methods;
- BCL singularity;
- Universe Mixmaster;
- Physics of elementary particles.
At the end1970sdiscoveries in particle physics led to the creation of modelsGrand Unification, which had a direct impact on cosmology.
In short, all the forces with which humanityencounters every day can be reduced to four categories - gravity, electromagnetism, strong and weak forces. The essence of Grand Unification theories is to somehow tie together the strong, weak and electromagnetic interactions. It is assumed that at extremely high energies they combine.
So, physicists Sheldon Glashow (yes, in honor of himnamed the character Sheldon Cooper from the TV series "The Big Bang Theory") and Steven Weinberg and Abdus Salam received the Nobel Prize in Physics in 1979 for combining the electromagnetic force with the weak force to form the concept of the electroweak force. Physicists working on the Grand Unified Theory seek to combine the electroweak force with the strong force to define the electron-nuclear force. Models had previously predicted it, but it had not yet been observed.
Third period: 1980–2000
New ideas that emerged during this period:
- inflationary cosmology;
- multiverse;
- Wave function of the Universe;
- The problem of cosmological measure;
- Children's universes and wormholes;
- Universes of Kaluza —Klein;
- String cosmology;
- The problem of cosmological stability.
It was during this period that the hypothesis appeared, according toin which the Universe in which we live may not be the only one that exists. In fact, there are an infinite number of universes, and they are all united in the multiverse. This concept may seem a little crazy, but if it's true, there is an alternate world. It's similar to the one we live in. Despite the fact that physicists claim that the multiverse is just a fiction, some scientists are trying to prove it. Even Stephen Hawking tried to solve her paradox.
There is a theory that fits into the hypothesis aboutexistence of the multiverse - a chaotic theory of inflation. According to it, inflation did not happen once and end, but continues and develops in different regions of space. By the way, it was in the “third period” of the development of cosmology that the inflation hypothesis appeared, which changes the idea of the physical state and the law of expansion of the Universe at the early stage of the Big Bang. It is noteworthy that it assumes a more accelerated expansion when compared with the standard model of a hot Universe.
Fourth period: from 2000 to today
As the authors of the article write, over the past 20 years, “the entire field of development of mathematical cosmology has matured beyond recognition compared to its image 50 years ago.”
Here are the main ideas of the last 20 years:
- M-theory and cosmology;
- Branes and parallel worlds;
- Topological problems and dynamic evolution;
- Generality in cosmology;
- Dark energy models.
One of the most popular and studied topicsin cosmology, dark energy, the main component of the current acceleration of the Universe. She has been the subject of intense attention since 1998. Then two teams of scientists, using different data sets and methods, discovered that the expansion rate of distant supernovae curves “upward” relative to their distance. Since then, this discovery has had a huge impact on cosmology and has confirmed the expectations of the cosmological constant - the so-called ΛCDM (Lambda-CDM model, English Cold Dark Matter, cold dark matter).
Today, dark energy models span the entirea range of possibilities, from the cosmological constant to scalar fields—the so-called quintessence—and modified theories of gravity. The truly amazing feature of this hypothetical type of energy is the fact that it combines a huge range of modified theories of gravity and other exotic forms of energy to search for the missing “link” of the Universe.
The general opinion of scientists is that itfills the entire space of the Universe and accounts for 72% of its mass (energy). According to other estimates, 66.2%. The other component of the remaining material in the Universe consists of dark matter, which makes up another 24%. But all the visible components of matter and radiation can amount to only a tiny 4%. How this happened is perhaps the biggest mystery of the Universe today.
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Based on: 100 years of mathematical cosmology: models, theories and problems, part A and part B.