Introduction to the universe

Universe; universe

The birth of the universe

The boundary of the universe we are observing now is about 65.438+000 billion light years. It is made up of many galaxies. The earth is an ordinary planet in the solar system, and the solar system is an ordinary star in the Milky Way. How did the stars, planets, comets and galaxies we observed form?

According to the theory of the universe, the universe we observed was concentrated in a very small, extremely high temperature and extremely high density primitive fireball at the early stage of its gestation. /kloc-0.5 billion to 20 billion years ago, the original fireball broke out and the birth history of our universe began.

After the Big Bang, it was 0.0 1 s, and temperature of the universe was about 1000 billion degrees. The main forms of matter are electrons, photons and neutrinos. After that, the substance quickly diffused and the temperature dropped rapidly. After the big bang, 1 sec dropped to 10 billion degrees. After the big bang 14 seconds, the temperature was about 3 billion degrees. After 35 seconds, at a high temperature of 300 million degrees, chemical elements began to form. The temperature keeps falling and atoms keep forming. The universe is full of gas clouds. Under the action of gravity, they formed a star system, which evolved over a long period of time and became the universe today.

The sum total of material phenomena. In a broad sense, it refers to the infinite change and eternal development of the material world, and in a narrow sense, it refers to the largest celestial system observed in a certain era. The latter is usually called Hubble volume, and our universe is now equivalent to the "main galaxy" in astronomy.

In February 2003, NASA announced their research results on the age of the universe to the world. According to the published data, the age of the universe should be 65.438+03.7 billion years old. In June 2003, the International Astrophysics Research Group declared that the exact age of the universe should be 14 1 100 million years old. The formation of the earth was about 4.5 billion years ago.

Etymological investigation of the universe first appeared in China's ancient books by Zhuangzi's theory of homogeneity. The meaning of "Yu" includes all directions, such as all places in the east, west, north and south. "Week" includes past, present, day and night, that is, all different specific times. At the end of the Warring States period, scholars said, "The past is the present, up and down in all directions." "Yu" refers to space, "Zhou" refers to time, and "universe" is the unity of time and space. Later, the word "universe" was used to refer to the whole objective real world. The concepts equivalent to the universe are "heaven and earth", "Gankun" and "Liuhe", but these concepts only refer to the spatial aspect of the universe. ? a target = _ blank href =/view/ 18686 . htm & gt。 Zhou He in Guan Zi refers to time, and He refers to space, which is the closest concept to the universe.

In the west, the word universe is called cosmos in English, кocMoc in Russian, kosmos in German and cosmos in French. Are derived from the Greek κoσμoζ. The ancient Greeks believed that the universe was created to produce order from chaos, and the original meaning of κoσμoζ was order. But in English, the more commonly used word for "universe" is Universe. This word has something to do with universitas. In the Middle Ages, people called universities a group of people who acted in the same direction and goal. In the broadest sense, universitas also refers to a unified whole composed of all ready-made things, that is, the universe. The universe and the universe often express the same meaning, but the difference is that the former emphasizes the sum of material phenomena, while the latter emphasizes the structure or construction of the whole 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, and they usually made naive speculations about the structure of the universe according to their living environment. During the Western Zhou Dynasty in China, people living on the land of China put forward the early theory of covering the sky, thinking that the sky was like a pot, lying on the flat ground; Later, it developed into the later theory of covering the sky, which believed that the shape of the earth was also arched. In the 7th century BC, Babylonians believed that the sky and the earth were arched, with the ocean around the earth and the mountains in the center. The ancient Egyptians imagined the universe as a big box, with the sky as the lid, the earth as the bottom and the Nile as the center of the earth. The ancient Indians imagined that the disc-shaped earth was thrown on several elephants, and the elephants stood on the backs of huge turtles. At the end of the 7th century BC, Thales in ancient Greece thought that the earth was a huge disk floating on the water, covered with an arched sky.

It was the ancient Greeks who first realized that the earth was spherical. In the 6th century BC, Pythagoras thought that the most beautiful three-dimensional figure was spherical from an aesthetic point of view, and advocated that celestial bodies and the earth where we live were both spherical. This concept was later inherited by many ancient Greek scholars, but it was not until 15 19 ~ 1522 that F. Magellan of Portugal led the expedition to complete the first round-the-world voyage that the concept that the earth was spherical was finally confirmed.

In the 2nd century AD, Ptolemy put forward a complete geocentric theory. According to this theory, the earth is stationary at the center of the universe, and the moon, sun, planets and outermost stars are all rotating around the earth at different speeds. In order to explain the unevenness of the apparent motion of the planet, he also thinks that the planet rotates around its center in this round, and the center of this round rotates around the earth along a uniform wheel. Geocentric theory has been circulating in Europe for 1000 years. 1543, N. Copernicus put forward the scientific Heliocentrism, thinking that the sun is located in the center of the universe and the earth is an ordinary planet, orbiting the sun in a circular orbit. 1609, J. Kepler revealed that the earth and planets revolve around the sun in elliptical orbits, which developed the Heliocentrism of Copernicus. In the same year, G Galileo took the lead in observing the sky with a telescope, and confirmed the correctness of Heliocentrism with a large number of observation facts. 1687, I Newton put forward the law of universal gravitation, which profoundly revealed the mechanical reasons for the motion of planets around the sun and gave Heliocentrism a solid mechanical foundation. After that, people gradually established the scientific concept of the solar system.

In Copernicus's image of the universe, the stars are just the light spots in the outermost starry sky. 1584, G. Bruno boldly canceled this layer of star sky and thought that the star was a distant sun. /kloc-in the first half of the 8th century, Bruno's speculation was recognized by more and more people because of E Harley's self-development of stars and J Bradley's scientific estimation of the distant distance of stars. /kloc-in the mid-8th century, T. Wright, I. Kant and J. H. Lambert speculated that the stars and galaxies covered all day constituted a huge celestial system. F. W. Herschel first counted the number of stars in a large number of selected areas in the sky and the ratio of bright stars to dark stars with a telescope by sampling statistics. 1785, the horizontal organization map of the Milky Way with uneven outline and the sun as the center was obtained for the first time, thus laying the foundation for the concept of the Milky Way. In the next century and a half, after H. shapley discovered that the sun was not in 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, the scientific concept of the Milky Way was finally established.

/kloc-In the middle of the 0/8th century, Kant and others also proposed that there are countless celestial bodies like us (referring to the Milky Way) in the whole universe. The "nebula" that looked like a cloud at that time was probably such a celestial system. Since then, it has experienced a tortuous exploration process of 170 years. It was not until 1924 that E.P. Hubble measured the distance of the Andromeda nebula with Cepheid parallax method, which confirmed the existence of extragalactic galaxies.

Over the past half century, through the study of extragalactic galaxies, people have not only discovered higher-level celestial systems such as galaxy clusters and superclusters, but also expanded our horizons to the depths of the universe as far as 20 billion light years.

The concept of the evolution of the universe was developed in China. As early as the Western Han Dynasty, Huai Nan Zi Zhen Xun pointed out: "There is a beginning and an end, a beginning and an end, and a husband has a beginning." It believes that the world has its opening time, its pre-opening period and its pre-opening period. Huai Nan Zi Tian Zi Xun also specifically outlines the process of the world from intangible material state to chaotic state and then to the generation and evolution of all things in the world. Ancient Greece also had a similar view. For example, leucippus suggested that due to the rotating motion of atoms in a vacuum, light matter escaped into outer space, while the rest of the matter constituted 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 point of view. 1644, R. Descartes proposed the vortex theory of the origin of the solar system; 1745, G.L.L Buffon put forward a theory of the origin of the solar system, which was caused by the collision between the great comet and the sun. 1755 and 1796, respectively, Kant and Laplace put forward the nebula theory of the origin of the solar system. The modern new nebula theory to explore the origin of the solar system is developed on the basis of Kant-Laplace nebula theory.

19 1 1 year, E. hertzsprung established the first color magnitude map of the cluster; 19 13 years, H.N. Russell drew the spectrum-luminosity diagram of the stars, that is, the Herro diagram. After obtaining this star map, Russell put forward the star evolution theory that stars start from red giants, first shrink to the main sequence, then slide down along the main sequence, and finally become red dwarfs. 1924, A.S. Eddington proposed the mass-luminosity relationship of stars; From 1937 to 1939, C. F. weizsacker and Bate revealed that the energy of stars comes from the nuclear reaction of hydrogen fusing into helium. These two discoveries led to the denial of Russell's theory and the birth of the scientific theory of star evolution. The study of the origin of galaxies started late. At present, it is generally believed that it evolved from primitive galaxies in the late stage of the formation of our universe.

19 17, A. Albert Einstein established a "static, finite and unbounded" model of the universe by using his newly established general theory of relativity, which laid the foundation of modern cosmology. 1922, G.D. Friedman discovered that according to Albert Einstein's field equation, the universe is not necessarily static, it can be either expanding or oscillating. The former corresponds to the open universe, while the latter corresponds to the closed universe. 1927, Lemaistre also proposed an expanding universe model. 1929, Hubble discovered that the redshift of galaxies is directly proportional to their distance, and established the famous Hubble law. This discovery is a strong support for the expansion model of the universe. In the mid-20th century, G Gamov and others put forward a cosmological model of the Big Bang, and they also predicted that according to this model, we should be able to observe the low-temperature background radiation in space. 1965 The discovery of microwave background radiation confirmed the prediction of Gamov et al. Since then, many people regard the Big Bang model as the standard model of the universe. 1980, Gus of the United States further proposed the skyrocketing universe model on the basis of the big bang universe model. This model can explain most of the important observed facts known at present.

The research results of contemporary astronomy show that the universe is a celestial system with hierarchical structure, diverse material forms and continuous movement and development.

Hierarchical planets are the most basic celestial systems. There are eight planets in the solar system: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Except mercury and venus, all other planets have satellites orbiting them. There is one satellite on the earth, and the moon and Saturn have the most satellites, with 17 confirmed. Planets, asteroids, comets and meteoroids all revolve around the central celestial body sun, forming the solar system. The sun accounts for 99.86% of the total mass of the solar system, with a diameter of about 6.5438+0.4 million kilometers, and the largest planet Jupiter has a diameter of about 6.5438+0.4 million kilometers. The size of the solar system is about 654.38+0.2 billion kilometers. There is evidence that there are other planetary systems outside our solar system. 250 billion sun-like stars 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 space, which looks like a discus from the side, but from the front? It is in the shape of a vortex. The diameter of the Milky Way is about 654.38+ million light years, and the sun is located in a spiral arm 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, which are called extragalactic galaxies, which is what we often call galaxies. It is observed that there is about 10 billion. Galaxies also gather into large and small groups called galaxy clusters. On average, each cluster has more than 100 galaxies with a diameter of tens of millions of light years. Thousands of galaxy clusters have been discovered. A small cluster of galaxies consisting of about 40 galaxies, including the Milky Way, is called the local cluster. Many galaxy clusters gather together to form a larger and higher-level celestial system, which is called supercluster. Supergalaxy clusters often have a flat shape, and their long diameter can reach hundreds of millions of light years. Usually, superclusters contain only a few clusters, and only a few superclusters have dozens of clusters. A supercluster composed of the local cluster and about 50 nearby clusters is called a local supercluster. At present, the astronomical observation range has been extended to the vast space of 20 billion light years, which is called the total galaxy.

The diversity of celestial bodies is very different, and there are various substances in the universe. Among the celestial bodies in the solar system, the surface temperature of Mercury and Venus is about 700K, and the temperature of distant Pluto towards the sun is only 50 K at the highest. The surface of Venus is covered with dense carbon dioxide atmosphere and sulfuric acid cloud, and the atmospheric pressure is about 50 atmospheres, while the surface atmosphere of Mercury and Mars is extremely thin, and the atmospheric pressure of Mercury is even less than 2× 10-9 mbar. Earth-like planets (Mercury, Venus and Mars) all have a solid surface, while wood-like planets are fluid planets. The average density of Saturn is 0.70g/cm3, which is smaller than that of water. The average density of Jupiter, Uranus and Neptune is slightly higher than that of water, while the density of Mercury, Venus and Earth is more than five times that of water. Most planets rotate in the forward direction, while Venus rotates in the reverse direction. The surface of the earth is full of vitality, while other planets are an empty and desolate world.

The sun is a common and typical star in the star world. It is found that some red giant stars are thousands of times the diameter of the sun. Neutron stars are only tens of thousands of times the diameter of the sun; The luminosity of Supergiant star is as high as several million times that of the sun, while the luminosity of white dwarfs is less than several hundred thousand times that of the sun. The density of red Supergiant star is as small as one millionth of that of water, while the density of white dwarfs and neutron stars can be as high as10000000 times and10000000000 times of that of water, respectively. The surface temperature of the sun is about 6000K, that of the O star is 30000K, and that of the infrared star is only about 600 K. The average magnetic field strength of the sun is 1× 10-4 Tesla, and the magnetic fields of some magnetic white dwarfs are usually thousands or tens of thousands of gauss (1 gauss = 10-). Some stars are basically constant in luminosity, while others are constantly changing, which is called variable stars. Some variable stars have periodic photometric changes, ranging from 1 hour to hundreds of days. The luminosity of some variable stars changes suddenly, among which the most drastic changes are nova and supernova, and their luminosity can be increased by tens of thousands or even hundreds of millions of times in a few days.

Stars tend to cluster into binary stars or clusters, which may account for 1/3 of the total number of stars. There are dozens, hundreds or even hundreds of thousands of star clusters. Cosmic matter not only forms stars and planets in dense form, but also forms interstellar matter in dispersed form. Interstellar matter includes interstellar gas and dust, with an average of only one atom per cubic centimeter, forming nebulae of various shapes in highly dense places. In addition to the stars and nebulae 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, rod-shaped spiral galaxies, lens galaxies and irregular galaxies. In the 1960s, many extragalactic objects were discovered, which are experiencing explosions or throwing out huge amounts of matter, and they are collectively called active galaxies, including various radio galaxies, Seifert galaxies, N-type galaxies, Makarian galaxies, BL-type celestial bodies in Boetes, quasars and so on. Many galactic nuclei have large-scale activities: airflow with a speed of several Qian Qian meters per second, energy output with a total energy of 65,438+0,055 Joules, mass and particle ejection, intense light changes and so on. There are various extreme physical states in the universe: ultra-high temperature, ultra-high pressure, ultra-high density, ultra-vacuum, ultra-high magnetic field, ultra-high speed motion, ultra-high speed rotation, ultra-large-scale space-time, superfluidity, superconductivity and so on. 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 movement and development, and the movement forms of celestial bodies are various, such as rotation, self-space movement (local movement), revolution around the center of the system and participation in the movement of the whole celestial body system. On the one hand, the moon goes around the earth, and at the same time it goes around the sun with the earth. On the one hand, the sun rotates, on the other hand, it moves in the direction of Wuxian at a speed of 20 km/s, and at the same time, it takes about 220 million years to take the whole solar system around the center of the Milky Way, and the Milky Way is also rotating and moving relative to neighboring galaxies. Local superclusters may also be expanding and rotating. The Milky Way is also expanding.

Modern astronomy reveals the origin and evolution of celestial bodies. Contemporary theories about the origin of the solar system hold that the solar system was probably formed by the gravitational contraction of a cloud of dust gas (primitive solar nebula) in the Milky Way galaxy 5 billion years ago (see The Origin of the Solar System). Stars are produced by nebulae, and their lives have gone through gravitational contraction stage, main sequence stage, red giant stage, late stage and dying stage. The origin of galaxies is closely related to the origin of the universe. The popular view is that 400,000 years after the Big Bang, the temperature dropped to 4,000 K, and the universe changed from a period dominated by radiation to a period dominated by matter. At this time, due to the gravitational instability caused by density fluctuation or the role of cosmic turbulence, protogalaxies gradually formed and then evolved into galaxy clusters and galaxies. The universe model of the Big Bang describes the origin and evolution history of our universe: our universe originated from a big bang 20 billion years ago, when the temperature was extremely high and the density was extremely high. With the expansion of the universe, it has gone through the evolution process from hot to cold, from dense to thin, from radiation to material, and it did not enter the stage of large-scale galaxy formation until1~ 2 billion years ago, and then gradually formed the universe we see today. 1980 proposed the skyrocketing universe model, which is a supplement to the thermal big bang universe model. It believes that in the very early stage of the universe, about 10-36 seconds after the birth of our universe, it experienced a skyrocketing stage.

Philosophical analysis of the concept of the universe Some cosmologists believe that our universe is the only universe; The Big Bang didn't explode at any point in space, but the whole universe itself. However, the newly proposed inflation model shows that our universe is only a very small part of the whole inflation region, and the regional scale after inflation is greater than 1026 cm, while our universe was only 10 cm at that time. It is also possible that this skyrocketing region is part of a larger material system starting from a chaotic state. This situation is just like the expansion of human understanding from the solar system universe to the galaxy universe and then to the large-scale universe in the history of science. Today's science is trying to push human understanding further to explore the "skyrocketing universe" and the "irregular chaotic universe". Our universe is not the only universe, but a part of a larger material system. The Big Bang was not an explosion of the whole universe itself, but an explosion of a part of that larger material system. Therefore, it is necessary to distinguish between philosophy and natural science. The philosophical concept of the universe reflects the infinitely diverse and constantly developing material world; The concept of the universe in natural science involves the largest celestial system observed by human beings in a certain era. The two concepts of the universe are general and individual. With the development of the concept of the universe in natural science, people's understanding of the infinite universe will gradually deepen and approach. A clear understanding of the differences and connections between these two concepts of the universe is of positive significance for upholding the Marxist theory of infinite universe and opposing the theory of finite universe, creationism, mechanism, agnosticism, philosophical substitution and cancellation.

The Creation of the Universe Some cosmologists believe that the most radical reform of the expansion model may be to observe that all matter and energy in the universe are generated from nothing. This view was not accepted by people before because there are many conservation laws, especially the conservation of baryon number and energy. However, with the development of the grand unified theory, the baryon number may not be conserved, and the gravitational energy in the universe can be roughly said to be negative, which accurately offsets the non-gravitational energy and the total energy is zero. So there is no problem that the known conservation laws prevent observing the evolution of the universe from scratch. This view of "making something out of nothing" includes two aspects in philosophy: ① ontology. It is wrong to think that "nothing" is absolute nothingness. This not only violates the known scientific practice of mankind, but also violates the inflation model itself. According to this model, the observed universe we study is only a small part of the whole skyrocketing region, and it is not absolutely "nothing" outside the observed universe. At present, the matter that observes the universe is transformed from the energy released by the false vacuum state. This vacuum energy is only a special form of matter and energy, and it is not created from absolute "nothing". If further, this vacuum energy comes from "nothing", then the whole observation universe comes from "nothing" in the final analysis, and this "nothing" can only be an unknown form of matter and energy. ② Epistemology and methodology. The concept of the universe involved in the inflation model is the concept of the universe in natural science. No matter how vast the universe is, as a limited material system, it also has its history of emergence, development and extinction. The inflation model combines the traditional big bang cosmology with the grand unified theory, and holds that the observed forms of matter and energy in the universe are not eternal, and their origins should be studied. It regards "nothingness" as an unknown form of matter and energy, and regards "nothingness" and "existence" as a pair of logical categories, and discusses how our universe has changed from "nothingness"-an unknown form of matter and energy to "existence"-a known form of matter and energy, which has certain significance in epistemology and methodology.

The origin of time and space Some people think that time and space is not eternal, but comes from a state without time and space. According to the existing physical theory, there is no "clock" and "ruler" to measure in the range of less than 10-43 seconds and 10-33 cm, so the concepts of time and space are invalid, and it is a physical world without time and space. This view that known space-time forms have their applicable boundaries is completely correct. Just as Newton's concept of time and space developed into a relativistic concept of time and space in history, it is inevitable to establish a new concept of time and space with the development of scientific practice today. Because the general theory of relativity fails within 10-43 seconds after BIGBANG, the quantum effect of gravity must be considered, so some people try to explore the origin of known space-time forms by quantizing space-time. All these works are beneficial, but we must not deny the objective existence of time and space as a form of material existence just because the development of human concept of time and space or the existing level of science and technology cannot measure the new form of time and space.

Since the 1960s, the relationship between human existence and the universe has emerged due to the proposal and discussion of the anthropic principle. According to the anthropic principle, there may be many universes with different physical parameters and initial conditions, but only universes with specific physical parameters and initial conditions can evolve into human beings, so we can only see a universe that allows human beings to exist. Anthropic principle uses human existence to constrain the possible initial conditions and physical laws in the past, reduce their arbitrariness and explain some cosmic phenomena, which is of certain significance in scientific methodology. But it has been suggested that the creation of the universe depends on the existence of human beings as observers. This view is debatable. Now, according to the inflation model, the states that were taken as the initial conditions by the traditional Big Bang model may have emerged from the very early evolution of the universe, and the evolution of the universe has almost become irrelevant to some details of the initial conditions. In this way, the above viewpoint of denying the objective existence of the universe by using the difficulty of initial conditions has lost its foundation. However, some people think that it is impossible to observe the overall structure of the universe because of the huge distance scale brought about by the skyrocketing. There are reasons for this concern, 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.

universe

The universe is the space where we live, and the original meaning of the word "Yu" means "up and down".

The earth is our home;

The earth is only the third planet in the solar system;

The solar system only settled on one side of the huge spiral arm of the Milky Way;

Of all the galaxies in the universe, the Milky Way may be very inconspicuous. ...

All these make up our universe:

The universe is the home of all celestial bodies.

The universe is also our time, and the original meaning of "Zhou" is "eternal".

Because our universe does not always exist, it also has a process of birth and growth. Modern science found that our universe was formed about 20 billion years ago. In a spectacular big bang, our universe was born! This is the famous big bang theory. )

Once the universe was formed, it has been in motion. Scientists found that the universe is expanding and the distance between stars is getting bigger and bigger.

The universe has no beginning, no end, no boundary, no birth and destruction, only the end and beginning of each stage. Our present universe was formed about 20 billion years ago. In a spectacular big bang, this stage of the universe began! The latest research shows that the Big Bang was born in a black hole, and the black hole pressed everything including photons to a point. At this time, even electrons, neutrons, protons and so on do not exist (what substance is smaller than electrons? Modern science and technology can't explain it, so it's called quark for the time being. At this time, there was an explosion at a higher level than nuclear fusion, which affected at least several billion light years, and a new cosmic era was born.

[English abbreviation]:

[English]: the universe; universe

[explanation]:

The sum total of material phenomena. In a broad sense, it refers to the infinite change and eternal development of the material world, and in a narrow sense, it refers to the largest celestial system observed in a certain era. The latter is usually called Hubble volume, and our universe is now equivalent to the "main galaxy" in astronomy.

Etymological investigation of the universe first appeared in China's ancient books by Zhuangzi's theory of homogeneity. The meaning of "Yu" includes all directions, such as all places in the east, west, north and south. "Week" includes past, present, day and night, that is, all different specific times. At the end of the Warring States period, scholars said, "The past is the present, up and down in all directions." "Yu" refers to space, "Zhou" refers to time, and "universe" is the unity of time and space. Later, the word "universe" was used to refer to the whole objective real world. The concepts equivalent to the universe are "heaven and earth", "Gankun" and "Liuhe", but these concepts only refer to the spatial aspect of the universe. Zhou He in Guan Zi refers to time, and He refers to space, which is the closest concept to the universe.

In the west, the word universe is called cosmos in English, кocMoc in Russian, kosmos in German and cosmos in French. Are derived from the Greek κoσμoζ. The ancient Greeks believed that the universe was created to produce order from chaos, and the original meaning of κoσμoζ was order. But in English, the more commonly used word for "universe" is Universe. This word has something to do with universitas. In the Middle Ages, people called universities a group of people who acted in the same direction and goal. In the broadest sense, universitas also refers to a unified whole composed of all ready-made things, that is, the universe. The universe and the universe often express the same meaning, but the difference is that the former emphasizes the sum of material phenomena, while the latter emphasizes the structure or construction of the whole 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, and they usually made naive speculations about the structure of the universe according to their living environment. During the Western Zhou Dynasty in China, people living on the land of China put forward the early theory of covering the sky, thinking that the sky was like a pot, lying on the flat ground; Later, it developed into the later theory of covering the sky, which believed that the shape of the earth was also arched. In the 7th century BC, Babylonians believed that the sky and the earth were arched, with the ocean around the earth and the mountains in the center. The ancient Egyptians imagined the universe as a big box, with the sky as the lid, the earth as the bottom and the Nile as the center of the earth. The ancient Indians imagined that the disc-shaped earth was thrown on several elephants, and the elephants stood on the backs of huge turtles. At the end of the 7th century BC, Thales in ancient Greece thought that the earth was a huge disk floating on the water, covered with an arched sky.

It was the ancient Greeks who first realized that the earth was spherical. In the 6th century BC, Pythagoras thought that the most beautiful three-dimensional figure was spherical from an aesthetic point of view, and advocated that celestial bodies and the earth where we live were both spherical. This concept was later inherited by many ancient Greek scholars, but it was not until 15 19 ~ 1522 that F. Magellan of Portugal led the expedition to complete the first round-the-world voyage that the concept that the earth was spherical was finally confirmed.

In the 2nd century AD, Ptolemy put forward a complete geocentric theory. According to this theory, the earth is stationary at the center of the universe, and the moon, sun, planets and outermost stars are all rotating around the earth at different speeds. In order to explain the unevenness of the apparent motion of the planet, he also thinks that the planet rotates around its center in this round, and the center of this round rotates around the earth along a uniform wheel. Geocentric theory has been circulating in Europe for 1000 years. 1543, N. Copernicus put forward the scientific Heliocentrism, thinking that the sun is located in the center of the universe and the earth is an ordinary planet, orbiting the sun in a circular orbit. 1609, J. Kepler revealed that the earth and planets revolve around the sun in elliptical orbits, which developed the Heliocentrism of Copernicus. In the same year, G Galileo took the lead in observing the sky with a telescope, and confirmed the correctness of Heliocentrism with a large number of observation facts. 1687, I Newton put forward the law of universal gravitation, which profoundly revealed the mechanical reasons for the motion of planets around the sun and gave Heliocentrism a solid mechanical foundation. After that, people gradually established the scientific concept of the solar system.

In Copernicus's image of the universe, the stars are just the light spots in the outermost starry sky. 1584, G. Bruno boldly canceled this layer of star sky and thought that the star was a distant sun. /kloc-in the first half of the 8th century, Bruno's speculation was recognized by more and more people because of E Harley's self-development of stars and J Bradley's scientific estimation of the distant distance of stars. /kloc-in the mid-8th century, T. Wright, I. Kant and J. H. Lambert speculated that the stars and galaxies covered all day constituted a huge celestial system. F. W. Herschel first counted the number of stars in a large number of selected areas in the sky and the ratio of bright stars to dark stars with a telescope by sampling statistics. 1785, the horizontal organization map of the Milky Way with uneven outline and the sun as the center was obtained for the first time, thus laying the foundation for the concept of the Milky Way. In the next century and a half, H. shapley discovered that the sun was not.