The answer to the question “What is the Big Bang?” can be obtained during a long discussion, since it takes a lot of time. I will try to explain this theory briefly and to the point. So, the Big Bang theory postulates that our Universe suddenly came into being approximately 13.7 billion years ago (everything came from nothing). And what happened then still affects how and in what ways everything in the Universe interacts with each other. Let's consider the key points of the theory.
What happened before the Big Bang?
The Big Bang theory includes a very interesting concept - singularity. I bet this makes you wonder: what is a singularity? Astronomers, physicists and other scientists are also asking this question. Singularities are believed to exist in the cores of black holes. A black hole is an area of intense gravitational pressure. This pressure, according to the theory, is so intense that the substance is compressed until it has an infinite density. This infinite density is called singularity. Our Universe is supposed to have started out as one of these infinitely small, infinitely hot, infinitely dense singularities. However, we have not yet come to the Big Bang itself. The Big Bang is the moment at which this singularity suddenly “exploded” and began to expand and created our Universe.
The Big Bang theory would seem to imply that time and space existed before our universe came into being. However, Stephen Hawking, George Ellis and Roger Penrose (and others) developed a theory in the late 1960s that attempted to explain that time and space did not exist before the expansion of the singularity. In other words, neither time nor space existed until the universe existed.
What happened after the Big Bang?
The moment of the Big Bang is the moment of the beginning of time. After the Big Bang, but long before the first second (10 -43 seconds), space experiences ultra-fast inflationary expansion, expanding 1050 times in a fraction of a second.
Then the expansion slows down, but the first second has not yet arrived (only 10 -32 seconds left). At this moment, the Universe is a boiling “broth” (with a temperature of 10 27 ° C) of electrons, quarks and other elementary particles.
The rapid cooling of space (up to 10 13 °C) allows quarks to combine into protons and neutrons. However, the first second has not yet arrived (there are still only 10 -6 seconds).
At 3 minutes, too hot to combine into atoms, the charged electrons and protons prevent the emission of light. The universe is a super-hot fog (10 8 °C).
After 300,000 years, the Universe cools to 10,000 °C, electrons with protons and neutrons form atoms, mainly hydrogen and helium.
1 billion years after the Big Bang, when the temperature of the Universe reached -200 °C, hydrogen and helium form giant “clouds” that will later become galaxies. The first stars appear.
Big bang
Big bang. This is the name of the theory, or rather one of the theories, of the origin or, if you like, the creation of the Universe. The name is perhaps too frivolous for such a terrifying and awe-inspiring event. Especially frightening if you have ever asked yourself very difficult questions about the universe.
For example, if the Universe is all that is, then how did it begin? And what happened before that? If space is not infinite, then what is beyond it? And where should this something actually fit? How can we understand the word “infinite”?
These things are difficult to understand. Moreover, when you start to think about it, you get an eerie feeling of something majestic and terrible. But questions about the universe are one of the most important questions that humanity has asked itself throughout its history.
What was the beginning of the existence of the Universe?
Most scientists are convinced that the existence of the Universe began with a tremendous big explosion of matter that occurred about 15 billion years ago. For many years, most scientists shared the hypothesis that the beginning of the Universe was laid by a grand explosion, which scientists jokingly dubbed the “Big Bang.” In their opinion, all matter and all space, which is now represented by billions and millions of galaxies and stars, 15 billion years ago fit into a tiny space no larger than a few words in this sentence.
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How was the Universe formed?
Scientists believe that 15 billion years ago this small volume exploded into tiny particles smaller than atoms, giving rise to the existence of the Universe. Initially it was a nebula of small particles. Later, when these particles combined, atoms were formed. Star galaxies were formed from atoms. Since that Big Bang, the Universe has continued to expand, like an inflating balloon.
Doubts about the Big Bang Theory
But over the past few years, scientists studying the structure of the Universe have made several unexpected discoveries. Some of them question the Big Bang theory. What can you do, our world does not always correspond to our convenient ideas about it.
Distribution of matter during an explosion
One problem is the way matter is distributed throughout the universe. When an object explodes, its contents scatter evenly in all directions. In other words, if matter was initially compressed into a small volume and then exploded, then the matter should have been evenly distributed throughout the space of the Universe.
The reality, however, is very different from the expected ideas. We live in a very unevenly filled Universe. When looking into space, individual clumps of matter appear at a distance from each other. Huge galaxies are scattered here and there throughout outer space. Between the galaxies there are huge areas of unfilled emptiness. For more high level galaxies are grouped into clusters - clusters, and these latter - into mega clusters. Be that as it may, scientists have not yet come to an agreement on the question of how and why exactly such structures were formed. In addition, a new, even more serious problem has recently arisen with everything.
The science that studies the Universe as a single whole and the Metagalaxy as part of the Universe is called cosmology. George Gamow, an American theoretical physicist, suggests that our Universe, i.e. Metagalaxy, born in a hot state with a temperature of about 10 32 K. Gamow called this model "Big Bang Cosmology". Gamow worked on this model for 10 years. In 1948 he published the theory " big bang" According to theory "Big Bang" our Universe is expanding. Expansion has begun 15 billion years ago from the initial very hot state. According to this theory, at the initial moment the matter of the Universe was in a state of physical vacuum. The physical vacuum was in an unstable, excited state, since it had enormous energy: w=, where g/cm 3 is the density of vacuum matter, and With– speed of light. The energy creates enormous pressure. At a moment in time 10 43 s., Due to the enormous pressure, vacuum inflation begins, i.e. the vacuum begins to lose energy. From the moment 10 ─43 s. up to 10 ─35 s, the vacuum matter expands exponentially and its size increases by 10 50 times. In the time interval from 10 ─35 s to 10 ─32 s, phase transition, i.e. the “Big Bang”, during which the vacuum state of matter through tunnel effect turns into a hot dense Universe with a temperature 10 32 K, with matter in the form electromagnetic waves(radio waves, infrared, visible, ultraviolet, x-rays and gamma rays). Thus, our Universe was born in the form of a fireball, which was called "Ilem"(Greek ylem - primary matter). Ilem was a neutral gas of electromagnetic waves and elementary particles. Due to fast extensions, matter of the universe cools down and the appearance of particles from radiation begins. In the beginning, the number of particles and antiparticles was equal. Then it happens spontaneous violation symmetry, this leads to the predominance of particles over antiparticles. In the first seconds after the explosion they are born hadrons(baryons and mesons). After approximately 1000 s after the explosion the temperature becomes approximately 10 10 K and the equality of the concentrations of protons and neutrons is violated for the reason that the lifetime of protons is equal 10 31 years, and the neutron lifetime lasts about 800 s. Neutrons decay and the ratios are established: 77% protons and 22% neutrons. In the time interval from 1000 s to 10,000 s, the formation of light hydrogen and helium atoms occurs. Almost all neutrons go into the formation of a helium nucleus, and the following relationship is established: 77% hydrogen and 22% helium. Scientists divide the time interval for the formation of the Universe into four “eras” in accordance with the prevailing form of existence of matter. 1. Hadron era lasts 0.0001 seconds. The hadron era is the era of heavy particles. The particle density is ρ>10 14 g/cm 3, and the temperature T>10 12 K. At the end of the era, a sudden violation of symmetry occurs, the equality of particles and antiparticles. The reason for the breaking of symmetry is considered to be non-conservation of the baryon charge. As a result, for every million (10 6) antiparticles there is a million plus one (10 6 +1) particle. 2. Era of leptons. The duration of the era is from 0.0001 s to 10 s, the temperature is from 10 10 K to 10 12 K, the density is from 10 4 to 10 14 g/cm 3 . In this era, the main role is played by light particles, taking part in reactions between protons and neutrons. Mutual transformations of protons into neutrons and vice versa occur. Mu-mesons, electrons, neutrinos and their antiparticles gradually accumulate. At the end of the era of leptons occurs annihilation of particles and antiparticles. Thus, in the Universe, antiparticles disappear, leaving particles and radiation. The Universe becomes transparent to electron neutrinos. These neutrinos have survived to this day. 3. The era of radiation. Its duration is 70 million years, the temperature decreases from 10 10 K to 3000 K, and the density from 10 4 to 10 -21 g/cm 3. By the beginning of the radiation era, the number of protons and neutrons is approximately equal. As the temperature decreases, the amount there are more protons due to neutron decay. At the end of the era, conditions arise for the formation of primary atoms, as a result of which a new era begins - the era of matter. 4. The era of substance. This era began 70 million years after the “Big Bang” with a temperature of about 3000K and a density of about 10 4 g/cm 3 . At the beginning of the era, the radiation density and the density of matter (particles) were equal - about 10 −26 g/cm 3, they were in conditions of thermal equilibrium. At equilibrium evolutionary process does not occur, i.e. matter cannot become more complex. However, as the Universe expands, matter cools and radiation cools according to different laws. The temperature of matter decreases in inverse proportion to the square of the size of the Universe: T substance ~1/R 2. The temperature of radiation decreases in inverse proportion to the size of the Universe: T radiation ~1/R. Hence, the substance cools much faster. The universe moves from an equilibrium state to a nonequilibrium state. Powers gravity creates instability, and turbulent motion creates shock waves. All this leads to fragmentation of the matter of the Universe. Small and large gas clouds are formed, consisting of radiation, elementary particles, hydrogen and helium atoms. In the time interval from 3 hours to 3 million years, stars are formed from small clouds, and entire galaxies are formed from large clouds. The mechanism of the formation of stars, American scientist Trumpler (1930) first explained the fact that the gas and dust cloud compresses and heats up, the pressure and temperature inside increase, slowing down the compression. At 20 million degrees it starts nuclear reaction, an explosion occurs and a new star appears. Our Sun made this journey in about 1 million years, about 5 billion years ago. The Big Bang theory has become almost as widely accepted a cosmological model as the Earth's rotation around the Sun. According to the theory, about 14 billion years ago, spontaneous vibrations in absolute emptiness led to the emergence of the Universe. Something comparable in size to a subatomic particle expanded to unimaginable sizes in a fraction of a second. But there are many problems in this theory that physicists are struggling with, putting forward more and more new hypotheses. From the theory it follows that all planets and stars were formed from dust scattered throughout space as a result of an explosion. But what preceded it is unclear: here our mathematical model of space-time stops working. The Universe arose from an initial singular state, to which modern physics cannot be applied. The theory also does not consider the causes of the singularity or the matter and energy for its occurrence. It is believed that the answer to the question of the existence and origin of the initial singularity will be provided by the theory of quantum gravity. Most cosmological models predict that the complete Universe is much larger than the observable part - a spherical region with a diameter of approximately 90 billion light years. We see only that part of the Universe, the light from which managed to reach the Earth in 13.8 billion years. But telescopes are getting better, we are discovering more and more distant objects, and there is no reason to believe that this process will stop. Since the Big Bang, the Universe has been expanding at an accelerating rate. The most difficult riddle modern physics is the question of what causes acceleration. According to the working hypothesis, the Universe contains an invisible component called “dark energy”. Theory big bang does not explain whether the Universe will expand indefinitely, and if so, what will this lead to - its disappearance or something else. Although Newtonian mechanics was supplanted by relativistic physics, it cannot be called erroneous. However, the perception of the world and the models for describing the Universe have completely changed. The Big Bang theory predicted a number of things that were not known before. Thus, if another theory comes to replace it, it should be similar and expand the understanding of the world. We will focus on the most interesting theories describing alternative models of the Big Bang. The Universe arose due to the collapse of a star in a four-dimensional Universe, according to scientists from the Perimeter Institute of Theoretical Physics. The results of their study were published by Scientific American. Niayesh Afshordi, Robert Mann and Razi Pourhasan say that our three-dimensional Universe became a kind of “holographic mirage” when a four-dimensional star collapsed. Unlike the Big Bang theory, which posits that the universe arose from an extremely hot and dense space-time where the standard laws of physics do not apply, the new hypothesis of a four-dimensional universe explains both the origins and its rapid expansion. According to the scenario formulated by Afshordi and his colleagues, our three-dimensional Universe is a kind of membrane that floats through an even larger universe that already exists in four dimensions. If this four-dimensional space had its own four-dimensional stars, they would also explode, just like the three-dimensional ones in our Universe. The inner layer would become a black hole, and the outer one would be thrown into space. In our Universe, black holes are surrounded by a sphere called the event horizon. And if in three-dimensional space this boundary is two-dimensional (like a membrane), then in a four-dimensional universe the event horizon will be limited to a sphere that exists in three dimensions. Computer simulations of the collapse of a four-dimensional star have shown that its three-dimensional event horizon will gradually expand. This is exactly what we observe, calling the growth of the 3D membrane the expansion of the Universe, astrophysicists believe. An alternative to the Big Bang is the Big Freeze. A team of physicists from the University of Melbourne, led by James Kvatch, presented a model of the birth of the Universe, which is more reminiscent of the gradual process of freezing amorphous energy than its release and expansion in three directions of space. Formless energy, according to scientists, like water, cooled to crystallization, creating the usual three spatial and one temporal dimensions. The Big Freeze theory challenges Albert Einstein's currently accepted assertion of the continuity and fluidity of space and time. It is possible that space has components - indivisible building blocks like tiny atoms or pixels in computer graphics. These blocks are so small that they cannot be observed, however, following the new theory, it is possible to detect defects that should refract the flow of other particles. Scientists have calculated such effects using mathematics, and now they will try to detect them experimentally. Ahmed Farag Ali of Benha University in Egypt and Saurya Das of the University of Lethbridge in Canada have proposed a new solution to the singularity problem by abandoning the Big Bang. They introduced the ideas of the famous physicist David Bohm into the Friedmann equation describing the expansion of the Universe and the Big Bang. “It's amazing that small adjustments can potentially solve so many issues,” says Das. The resulting model combines general theory relativity and quantum theory. It not only denies the singularity that preceded the Big Bang, but also does not admit that the Universe will eventually contract back to its original state. According to the data obtained, the Universe has a finite size and an infinite lifetime. In physical terms, the model describes a Universe filled with a hypothetical quantum fluid, which consists of gravitons - particles that provide gravitational interaction. The scientists also say their findings correlate with latest results measurements of the density of the Universe. The term “inflation” refers to the rapid expansion of the Universe, which occurred exponentially in the first moments after the Big Bang. The inflation theory itself does not disprove the Big Bang theory, but only interprets it differently. This theory solves several fundamental problems in physics. According to the inflationary model, shortly after its birth the Universe is very short time expanded exponentially: its size doubled many times. Scientists believe that in 10 to -36 seconds, the Universe increased in size by at least 10 to 30 to 50 times, and possibly more. At the end of the inflationary phase, the Universe was filled with superhot plasma of free quarks, gluons, leptons and high-energy quanta. The concept implies what exists in the world many universes isolated from each other with different device Physicists have come to the conclusion that the logic of the inflationary model does not contradict the idea of the constant multiple birth of new universes. Quantum fluctuations - the same as those that created our world - can arise in any quantity if the conditions are right for them. It is quite possible that our universe has emerged from the fluctuation zone that formed in the predecessor world. It can also be assumed that someday and somewhere in our Universe a fluctuation will form that will “blow out” a young Universe of a completely different kind. According to this model, daughter universes can bud off continuously. Moreover, it is not at all necessary that the same physical laws are established in new worlds. The concept implies that in the world there are many universes isolated from each other with different structures. Paul Steinhardt, one of the physicists who laid the foundations of inflationary cosmology, decided to develop this theory further. The scientist, who heads the Center for Theoretical Physics at Princeton, together with Neil Turok from the Perimeter Institute for Theoretical Physics, outlined an alternative theory in the book Endless Universe: Beyond the Big Bang ("The Infinite Universe: Beyond the Big Bang"). Their model is based on a generalization of quantum superstring theory known as M-theory. According to it, the physical world has 11 dimensions - ten spatial and one temporal. Spaces of lower dimensions, the so-called branes, “float” in it. (short for "membrane"). Our Universe is simply one of these branes. The Steinhardt and Turok model states that the Big Bang occurred as a result of the collision of our brane with another brane - an unknown universe. In this scenario, collisions occur endlessly. According to the hypothesis of Steinhardt and Turok, another three-dimensional brane “floats” next to our brane, separated by a tiny distance. It is also expanding, flattening and emptying, but after a trillion years the branes will begin to move closer together and eventually collide. This will highlight huge amount energy, particles and radiation. This cataclysm will trigger another cycle of expansion and cooling of the Universe. From the model of Steinhardt and Turok it follows that these cycles have existed in the past and will certainly repeat in the future. The theory is silent about how these cycles began. Another hypothesis about the structure of the universe says that our entire world is nothing more than a matrix or a computer program. The idea of what the universe is digital computer, first put forward by German engineer and computer pioneer Konrad Zuse in his book Calculating Space (“Computational space”). Among those who also considered the Universe as a giant computer are physicists Stephen Wolfram and Gerard 't Hooft. Digital physics theorists propose that the universe is essentially information, and therefore computable. From these assumptions it follows that the Universe can be considered as the result of a computer program or a digital computing device. This computer could be, for example, a giant cellular automaton or a universal Turing machine. Indirect evidence virtual nature of the universe called the uncertainty principle in quantum mechanics According to the theory, every object and event physical world comes from asking questions and recording yes or no answers. That is, behind everything that surrounds us, there is a certain code, similar to the binary code of a computer program. And we are a kind of interface through which access to the data of the “universal Internet” appears. An indirect proof of the virtual nature of the Universe is called the uncertainty principle in quantum mechanics: particles of matter can exist in an unstable form, and are “fixed” in a specific state only when they are observed. Digital physicist John Archibald Wheeler wrote: “It would not be unreasonable to imagine that information resides in the core of physics as in the core of a computer. Everything is from the bit. In other words, everything that exists - every particle, every force field, even the space-time continuum itself - receives its function, its meaning and, ultimately, its very existence."
What's wrong with the Big Bang Theory
The Universe is like a mirage of a black hole
Big Freeze
Universe without beginning and end
Endless chaotic inflation
Cyclic theory
Universe
like a computer