A mystery beyond the universe (question)

Universe

In the West, the word universe is called cosmos in English, кocMoc in Russian, kosmos in German, and cosmos in French. They are all derived from the Greek κoσμoζ. The ancient Greeks believed that the creation of the universe produced order from chaos. The original meaning of κoσμoζ is order. But the word more commonly used to mean "universe" in English is universe. This word is related to universitas. In the Middle Ages, a group of people acting together in the same direction toward the same goal was called a universitas. In the broadest sense, universitas also refers to the unified whole composed of all ready-made things, that is, the universe. Universe and cosmos often mean the same thing, but the difference is that the former emphasizes the sum of material phenomena, while the latter emphasizes the structure or structure of the overall universe.

The development of the concept of the universe The development of the concept of the structure of the universe In ancient times, people's understanding of the structure of the universe was in a very naive state. They usually made naive speculations about the structure of the universe based on their living environment. During the Western Zhou Dynasty in China, people living on the land of China put forward the early theory of sky-gap, which believed that the sky was like a pot, upside down on the flat earth; later it developed into the later theory of sky-gap, which believed that the shape of the earth was also arched. . In the 7th century BC, the Babylonians believed that the sky and the earth were arched, with the earth surrounded by oceans and mountains in the center. The ancient Egyptians imagined the universe as a large box with the sky as the lid, the earth as the bottom, and the Nile River in the center of the earth. Ancient Indians imagined that the disk-shaped earth was carried on a few elephants, and the elephants stood on the backs of huge turtles. At the end of the 7th century BC, Thales of ancient Greece believed that the earth was a huge disk floating on the water. , covered with an arched sky.

The first people to realize that the earth is spherical were the ancient Greeks. In the 6th century BC, Pythagoras started from the aesthetic concept and believed that the most beautiful of all three-dimensional figures was the sphere. He advocated that the celestial bodies and the earth we live on are both spherical. This concept was inherited by many ancient Greek scholars later, but it was not until 1519-1522, when F. Magellan of Portugal led an expedition to complete the first circumnavigation of the world that the concept that the earth was spherical was finally confirmed.

In the 2nd century AD, C. Ptolemy proposed a complete geocentric theory. This theory holds that the earth is motionless in the center of the universe, and that the moon, sun, planets, and the outermost stars are all revolving around the earth at different speeds. In order to explain the non-uniformity of planetary motion, he also believed that the planet rotates around its center on an epicycle, and the center of the epicycle rotates around the earth along the deferent. The geocentric theory has been circulating in Europe for more than 1,000 years. In 1543, N. Copernicus proposed the scientific heliocentric theory, which believed that the sun was located at the center of the universe and the earth was an ordinary planet orbiting the sun in a circular orbit. It was not until Copernicus established the heliocentric theory in the 16th century that it was generally realized that the earth is one of the planets orbiting the sun, and the eight planets, including the earth, constitute a planetary system that orbits the sun - the main member of the solar system. In 1609, J. Kepler revealed that the earth and the planets revolve around the sun in elliptical orbits, developing Copernicus' heliocentric theory. In the same year, Galileo Galilei took the lead in observing the sky with a telescope and confirmed it with a large number of observational facts. The correctness of the heliocentric theory. In 1687, I. Newton proposed the law of universal gravitation, which profoundly revealed the mechanical reasons for the movement of planets around the sun, giving the heliocentric theory a solid mechanical foundation. After that, people gradually established a scientific concept of the solar system.

In Copernicus's picture of the universe, stars are just points of light in the outermost stellar sky. In 1584, Giordano Bruno boldly abolished this sidereal sky and believed that the stars were all distant suns. In the first half of the 18th century, due to E. Halley's development of the proper motion of stars and J. Bradley's scientific estimation of the distant distance of stars, Bruno's speculation gained more and more support.

In the mid-18th century, T. Wright, I. Kant and J.H. Lambert speculated that the stars and the Milky Way all over the sky constitute a huge celestial system. Friedrich William Herschel pioneered the method of sampling statistics, using a telescope to count the number of stars in a large number of selected areas in the sky and the ratio of bright stars to dark stars. In 1785, he first obtained a flat and flat picture. , a structural diagram of the Milky Way with jagged outlines and the sun at the center, thus laying the foundation for the concept of the Milky Way. In the next century and a half, H. Shapley discovered that the sun is not at the center of the Milky Way, J.H. Oort discovered the rotation and spiral arms of the Milky Way, and many people measured the diameter and thickness of the Milky Way, and the scientific concept of the Milky Way was finally established. .

In the mid-18th century, Kant and others also proposed that there are countless celestial systems like ours (referring to the Milky Way) in the entire universe. The "nebula" that looked like a cloud at that time was probably just such a celestial system. After that, it went through a tortuous exploration process for 170 years. It was not until 1924 that E.P. Hubble confirmed the existence of extragalactic galaxies using the Cepheid parallax method to measure the distance to the Andromeda Nebula.

In the past half century, through the study of extragalactic galaxies, people have not only discovered higher-level celestial systems such as galaxy clusters and supergalaxy clusters, but also expanded our field of vision to as far as 20 billion lights years deep in the universe.

The development of the concept of cosmic evolution in China, as early as the Western Han Dynasty, "Huainanzi Chu Zhenxun" pointed out: "There is a beginning, there is a beginning, there is a beginning, there is a beginning, and there is a beginning. "The world has its beginning, its period before its opening, and its period before its opening." "Huainanzi Tianwen Xun" also specifically outlines the process of the world from the invisible material state to the chaotic state to the creation and evolution of everything in the heaven and earth. In ancient Greece, there was a similar view. For example, Leucippus proposed that due to the vortex motion of atoms in empty space, light matter escaped into the external void, while the remaining matter formed spherical celestial bodies, thus forming our world.

After the concept of the solar system was established, people began to explore the origin of the solar system from a scientific perspective. In 1644, R. Descartes proposed the vortex theory of the origin of the solar system; in 1745, G.L.L. Buffon proposed a theory of the origin of the solar system that resulted from the collision of a large comet with the sun; in 1755 and 1796, Kant and Rapp Lars each proposed a nebular theory of the origin of the solar system. The modern neonebula theory that explores the origin of the solar system was developed on the basis of the Kant-Laplace nebula theory.

In 1911, E. Hertzsprung established the first color and magnitude map of the Milky Way star cluster; in 1913, Bertrand Arthur William Russell drew the spectrum of stars - The photometric diagram is the Hertz-Rubber diagram. After obtaining this diagram, Russell proposed a stellar evolution theory in which a star starts from a red giant star, first shrinks into the main sequence, then slides down the main sequence, and finally becomes a red dwarf star. In 1924, Arthur Stanley Eddington proposed the mass-light relationship of stars; from 1937 to 1939, C.F. Weizsacker and Bethe revealed that the energy of stars comes from the nuclear reaction of hydrogen fusion into helium. These two discoveries led to the denial of Russell's theory and the birth of the scientific theory of stellar evolution. The study of the origin of galaxies started relatively late. It is currently generally believed that they evolved from proto-galaxies in the later stages of the formation of our universe.

In 1917, A. Albert Einstein used his newly created general theory of relativity to establish a "static, finite, and unbounded" universe model, laying the foundation for modern cosmology. In 1922, G.D. Friedman discovered that, according to Albert Einstein's field equations, the universe was not necessarily static; it could be expanding or oscillating. The former corresponds to the open universe, and the latter corresponds to the closed universe. In 1927, G. Lema?tre also proposed an expanding universe model. In 1929, Hubble discovered that the red shift of a galaxy is proportional to its distance, establishing the famous Hubble's law. This discovery is strong support for the expanding universe model.

In the middle of the 20th century, G. Gamow and others proposed the hot big bang universe model. They also predicted that according to this model, low-temperature background radiation should be observed in the universe. The discovery of microwave background radiation in 1965 confirmed the predictions of Gamow et al. Since then, many people have regarded the Big Bang model of the universe as the standard model of the universe. In 1980, Guth of the United States further proposed the inflationary universe model based on the hot big bang universe model. This model can explain most of the important observations currently known.

Picture of the Universe Contemporary astronomy research results show that the universe is a celestial body system with a hierarchical structure, diverse material forms, and constant movement and development.

Hierarchy Planets are the most basic celestial system. There are eight major planets in the solar system: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. (Pluto is currently expelled from the planet and downgraded to a dwarf planet). Except for Mercury and Venus, other planets have satellites orbiting them. The Earth has one satellite, the moon, and Saturn has the most satellites, with 26 confirmed ones. Planets, asteroids, comets, and meteoroids all orbit the central celestial body, the sun, and form the solar system. The sun accounts for 99.86% of the total mass of the solar system, and its diameter is about 1.4 million kilometers. The diameter of the largest planet, Jupiter, is about 140,000 kilometers. The size of the solar system is about 12 billion kilometers (with Pluto as the boundary). There is evidence that other planetary systems exist outside our solar system. 250 billion stars similar to the sun and interstellar matter constitute a larger celestial system - the Milky Way. Most of the stars and interstellar matter in the Milky Way are concentrated in an oblate spherical space. It looks like a "discus" when viewed from the side, and it looks like a vortex when viewed from the front. The diameter of the Milky Way is about 100,000 light-years. The sun is located in one of the spiral arms of the Milky Way, about 30,000 light-years away from the center of the Milky Way. There are many similar celestial systems outside the Milky Way, called extragalactic galaxies, often referred to as galaxies. Approximately 1 billion have been observed. Galaxies are also gathered into large and small groups, called galaxy clusters. On average, there are about a hundred galaxies in each galaxy cluster, with a diameter of tens of millions of light-years. Tens of thousands of galaxy clusters have been discovered. A small cluster of about 40 galaxies, including the Milky Way, is called the Local Group. Several galaxy clusters come together to form a larger, higher-level celestial system called a supercluster. Superclusters often have an elongated shape, with diameters up to hundreds of millions of light-years. Usually superclusters contain only a few galaxy clusters, and only a few superclusters contain dozens of galaxy clusters. The local group of galaxies and the supercluster of about 50 nearby galaxies is called the local supercluster. At present, the scope of astronomical observation has expanded to a vast space of 20 billion light years, which is called the total galaxy.

Diversity Celestial bodies are extremely diverse, and the matter in the universe is in various shapes and forms. Among the solar system objects, the surface temperature of Mercury and Venus is about 700K, and the temperature of the distant Pluto's sunward side is only 50K at its highest. The surface of Venus is covered with a dense carbon dioxide atmosphere and sulfuric acid clouds, with an air pressure of about 50 atmospheres. The surface atmosphere of Mercury and Mars is However, it is extremely thin. The atmospheric pressure of Mercury is even less than 2×10-9 millibars. The terrestrial planets (Mercury, Venus, Mars) all have a solid surface, but the Jupiter-like planets are fluid planets. The average density of Saturn is 0.70 g/ cm3, which is smaller than the density of water. The average density of Jupiter, Uranus, and Neptune is slightly greater than the density of water, while the density of Mercury, Venus, Earth, etc. is more than 5 times the density of water; most planets rotate in the same direction. , while Venus rotates in the opposite direction; the surface of the earth is full of life, while other planets are empty and desolate worlds.

The sun is a common and typical star in the star world. It has been found that some red giants have diameters thousands of times that of the sun. The diameter of a neutron star is only tens of thousands of times that of the sun; the luminosity of a supergiant star is millions of times that of the sun, but the luminosity of a white dwarf is less than one hundred thousand times that of the sun. The material density of red supergiants is as small as one millionth of the density of water, while the densities of white dwarfs and neutron stars can be as high as 100,000 and 100 billion times the density of water respectively. The surface temperature of the sun is about 6000K, the surface temperature of O-type stars reaches 30000K, and the surface temperature of infrared stars is only about 600K.

The sun's universal magnetic field strength is on average 1×10-4 Tesla. The magnetic field of some magnetic white dwarfs is usually thousands or tens of thousands of Gauss (1 Gauss = 10-4 Tesla), while the magnetic field strength of pulsars can be as high as ten. Trillion Gaussians. Some stars have a basically constant luminosity, while some stars have a luminosity that is constantly changing, and they are called variable stars. Some variable stars have a periodic change in luminosity, ranging from 1 hour to hundreds of days. The luminosity changes of some variable stars are sudden. Among them, the most dramatic changes are novae and supernovae. In a few days, their luminosity can increase tens of thousands or even hundreds of millions of times.

Stars often gather into binaries or clusters of stars in space, and they may account for 1/3 of the total number of stars. There are also star clusters composed of dozens, hundreds or even hundreds of thousands of stars gathered together. In addition to forming stars, planets, etc. in a dense form, the matter in the universe also forms interstellar matter in a diffuse form. Interstellar matter includes interstellar gas and dust, with an average of only one atom per cubic centimeter, and various nebulae of different shapes are formed in highly dense places. In addition to stars, nebulae and other objects that emit visible light, there are also ultraviolet objects, infrared objects, X-ray sources, gamma-ray sources and radio sources in the universe.

Galaxies can be divided into elliptical galaxies, spiral galaxies, barred spiral galaxies, lenticular galaxies and irregular galaxies according to their shapes. In the 1960s, many extragalactic objects were discovered that were undergoing explosion processes or ejecting huge amounts of matter. They were collectively called active galaxies, including various radio galaxies, Seyfert galaxies, N-type galaxies, Markarian galaxies, and Lacerta. BL type objects, quasars, etc. Many galactic nuclei have large-scale activities: gas flows with speeds of thousands of kilometers per second, energy output with a total energy of 1055 joules, huge matter and particle ejections, strong light changes, etc. There are various extreme physical states in the universe: ultra-high temperature, ultra-high pressure, ultra-high density, ultra-vacuum, ultra-strong magnetic field, ultra-high-speed motion, ultra-high-speed rotation, ultra-large-scale time and space, superfluidity, superconductivity, etc. It provides an ideal experimental environment for us to understand the objective material world.

Movement and development The celestial bodies in the universe are in eternal motion and development. The motions of celestial bodies are diverse, such as rotation, respective space motion (primary motion), revolution around the center of the system, and participation in the entire celestial body. System movement, etc. The moon rotates on its axis, orbits the earth on the one hand, and revolves around the sun with the earth on the other. On the one hand, the sun rotates, and on the other hand, it moves toward the constellation Hercules at a speed of 20 kilometers/second. At the same time, it takes the entire solar system to orbit the center of the Milky Way at a speed of 250 kilometers/second. It takes about 220 million years to complete one revolution. The Milky Way is also spinning and moving relative to neighboring galaxies. The local supercluster may also be expanding and rotating. The total galaxy is also expanding.

Modern astronomy has revealed the origin and evolution of celestial bodies. Contemporary theories about the origin of the solar system believe that the solar system was probably gradually formed due to the gravitational contraction of a dust and gas cloud (primitive solar nebula) in the Milky Way 5 billion years ago (see Origin of the Solar System). A star is produced from a nebula, and its life goes through the gravitational contraction stage, the main sequence stage, the red giant stage, the late stage and the terminal stage. The origin of galaxies is closely related to the origin of the universe. The popular view is that 400,000 years after the hot Big Bang occurred in the universe, the temperature dropped to 4000K, and the universe transformed from a radiation-dominated period to a matter-dominated period. At this time, perhaps due to density fluctuations The gravitational instability formed, or due to the effect of cosmic turbulence, gradually formed proto-galaxies, and then evolved into galaxy clusters and galaxies. The hot big bang universe model depicts the origin and evolution history of our universe: Our universe originated from a big explosion 20 billion years ago, which was extremely hot and dense at that time. As the universe expanded, it experienced an evolution from hot to cold, from dense to rarefied, from a period dominated by radiation to a period dominated by matter. It was not until 1 to 2 billion years ago that it entered the stage of large-scale formation of galaxies. Since then, the universe we see today gradually formed. The inflationary universe model proposed in 1980 is a complement to the hot big bang universe model. It believes that in the very early days of the universe, about 10-36 seconds after the birth of our universe, it experienced an inflationary stage.

Philosophical Analysis Concept of the Universe Some cosmologists believe that our universe is the only universe; the Big Bang is not the explosion at any point in the universe, but the explosion of the entire universe itself. However, the newly proposed inflation model shows that our universe is only a very small part of the entire inflation region. The size of the region after inflation is larger than 1026 centimeters, while our universe was only 10 centimeters at that time. It is also possible that this region of inflation is part of a larger system of matter that began in a state of random chaos. This situation is just like the history of science in which human understanding has expanded from the solar system to the galaxy universe and then to the large-scale universe. Today's science is working hard to further advance human understanding toward some kind of exploratory "inflationary universe" and "irregular universe". The chaotic universe" moves forward. Our universe is not the only universe, but a part of a larger material system. The Big Bang was not the explosion of the entire universe itself, but the explosion of a part of that larger material system. Therefore, it is necessary to distinguish the concepts of the universe at two different levels, philosophy and natural science. The concept of the philosophical universe reflects the infinitely diverse and eternally developing material world; the concept of the natural science universe involves the largest celestial system that humans can observe in a certain era. The relationship between the two concepts of the universe is that of general and individual. With the development of the concept of the universe in natural science, people will gradually deepen and approach the understanding of the infinite universe. Clarifying the differences and connections between the two concepts of the universe is of positive significance for adhering to the Marxist theory of universe infinity and opposing universe finiteism, creationism, mechanism, agnosticism, philosophical substitution theory and eliminativism.

The Creation of the Universe Some cosmologists believe that the most radical reform of the inflationary model may be the observation that all matter and energy in the universe came from nothing. The reason why this view was not available to people before Accepted because there are many conservation laws, especially the conservation of baryon number and the conservation of energy. But with the development of grand unified theories, it is possible that the baryon number is not conserved, and the gravitational energy in the universe can be roughly said to be negative and exactly cancel the non-gravitational energy, with the total energy being zero. Therefore, there is no known conservation law that prevents the observed universe from evolving from nothing. This view of "creating something out of nothing" includes two aspects in philosophy: ①Ontological aspect. It would be a mistake to think that "nothing" is absolute nothingness. Not only does this violate scientific practice known to man, but it also violates the inflationary model itself. According to this model, the observed universe we study is only a very small part of the entire inflationary region, and there is not absolute "nothing" outside the observed universe. The matter currently observed in the universe is transformed from the energy released from the false vacuum state. This vacuum energy is precisely a special form of matter and energy, and is not created from absolute "nothing". If it is further said that this vacuum energy originated from "nothing", and therefore the entire observed universe ultimately originated from "nothing", then this "nothing" can only be an unknown form of matter and energy. ②Epistemology and methodology. The concept of the universe involved in the inflationary model is the concept of the universe of natural science. No matter how huge this universe is, as a limited material system, it also has a history of its creation, development and destruction. The inflationary model combines traditional big bang cosmology with grand unified theory, believing that the forms of matter and energy in the observed universe are not eternal, and their origins should be studied. It regards "nothing" as an unknown form of matter and energy, "nothing" and "being" as a pair of logical categories, and explores how our universe transforms from "nothing", an unknown form of matter and energy, into "nothing". There are”—known forms of matter and energy, which has certain epistemological and methodological implications.

The Origin of Space and Time Some people believe that time and space are not eternal, but arise from a state of no time and no space. According to the existing physical theory, within the range of less than 10-43 seconds and 10-33 centimeters, there is no "clock" and "ruler" that can be measured. Therefore, the concepts of time and space fail, and there is no time. and the physical world of space. This view is entirely correct in proposing that known forms of spacetime have limits to which they apply.

Just as the Newtonian view of time and space in history developed into the relativistic view of time and space, today's development of scientific practice will inevitably require the establishment of a new view of time and space. Since the general theory of relativity fails within 10-43 seconds after the Big Bang, the quantum effects of gravity must be considered. Therefore, some people try to explore the origin of known space-time forms through the quantization of space-time. These works are all beneficial, but we must not deny the objective existence of time and space as forms of material existence because of the development of human concepts of time and space or the inability to measure new forms of time and space at the current level of science and technology.

Man and the universe Since the 1960s, due to the proposal and discussion of the anthropic principle, the issue of the relationship between human existence and the creation of the universe has emerged. The anthropic principle holds that there may be many universes with different physical parameters and initial conditions, but only universes with specific values ??of physical parameters and initial conditions can evolve humans, so we can only see one universe that allows humans to exist. The anthropic principle uses human existence to constrain the initial conditions and physical laws that may have existed in the past, reducing their arbitrariness and allowing some cosmological phenomena to be explained. This has certain significance in scientific methodology. But some people have suggested that the creation of the universe depends on the existence of humans as observers. This view is questionable. Now according to the inflationary model, those states that are used as initial conditions by the traditional big bang model may have arisen from the evolution of the very early universe, and the evolution of the universe has become almost independent of some details of the initial conditions. This makes the above-mentioned view of using the difficulties of initial conditions to deny the objective reality of the universe lose its foundation. But some believe that the huge distance scales caused by inflation make it impossible to observe the structure of the universe as a whole. This worry has its reasons, but if the inflation model is correct, with the development of scientific practice, it will be possible to break through the difficulties in human understanding.