universe; Cosmos
the sum of material phenomena. In a broad sense, it refers to the infinite variety 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 often called hubble volume, our universe, and now it is equivalent to the "master galaxy" in astronomy.
etymological study: The word universe was first used in China's ancient books by Zhuangzi's Theory of All Things. The meaning of "Yu" includes all directions, such as all places in the east, west, north and south. "Zhou" includes past, present, day and night, that is, all different specific times. At the end of the Warring States Period, Shi Jiao said: "The four directions are up and down, and the past is the present." "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. Concepts equivalent to the universe include "heaven and earth", "Gankun" and "Liuhe", but these concepts only refer to the space aspect of the universe. The word "Zhou He" in Guanzi refers to time, and "He" refers to space, which is the closest to the concept of "universe".
in the west, the word universe is called cosmos in English, кocMoc in Russian, kosmos in German and cosmos in French. They all originated from the Greek κoσμoζ. The ancient Greeks believed that the creation of the universe was to produce order from chaos, and κoσμoζ was originally meant to be order. But the word that is more often used to mean "universe" in English is Universe. This word is related to universitas. In the Middle Ages, people called universitas a group of people who acted in the same direction and towards the same goal. 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 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 own 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, which believed that the sky was like a pot, upside down on the flat land; 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, the earth was surrounded by oceans, and the mountain was in the center. The ancient Egyptians imagined the universe as a big box with the sky as the lid and the earth as the bottom, with the Nile at the center of the earth. Ancient Indians imagined that the disc-shaped earth was lost on several elephants, while 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 disc 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, from the aesthetic point of view, believed that the most beautiful three-dimensional figure was spherical, and advocated that celestial bodies and the earth where we lived were spherical. This concept was later inherited by many ancient Greek scholars, but it was not until 1519 ~ 1522, when 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, C. Ptolemy put forward a complete geocentric theory. This theory holds that the earth is motionless in the center of the universe, and the moon, the sun, the planets and the outermost stars are 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, while the center of this round rotates around the earth along the uniform wheel. Geocentric theory has been circulating in Europe for more than 1 years. In 1543, N. Copernicus put forward the scientific Heliocentrism, arguing that the sun is located in the center of the universe, while the earth is an ordinary planet revolving around the sun in a circular orbit. In 169, J. Kepler revealed that the Earth and the 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 through a telescope, and confirmed the correctness of Heliocentrism with a large number of observation facts. In 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 a scientific concept of the solar system.
In Copernicus's cosmic image, stars are just light spots in the outermost star sky. In 1584, G. Bruno boldly canceled this layer of stellar sky, thinking that stars are distant suns. In the first half of the 18th century, Bruno's speculation was approved 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. In the mid-18th century, T. Wright, I. Kant and J. H. Lambert speculated that the stars and galaxies that covered the whole day constituted a huge celestial system. F. W. Herschel first used the method of sampling statistics 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 with a telescope. In 1785, he first obtained a flat and flat structure map of the Milky Way with uneven contours and the sun centered, thus laying the foundation for the concept of the Milky Way. In the next century and a half, the scientific concept of the Milky Way was finally established 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.
in the middle of the 18th century, Kant and others also proposed that there are countless celestial systems like ours (referring to the Milky Way) in the whole universe. At that time, the "nebula" that looked like a cloud was probably such a celestial system. After 17 years of tortuous exploration, it was not until 1924 that E.P. Hubble confirmed the existence of extragalactic galaxies by measuring the distance of Andromeda nebula with Cepheid parallax method.
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 supercluster, but also expanded our horizons to the depths of the universe as far as 2 billion light years.
The concept of the evolution of the universe developed in China. As early as the Western Han Dynasty, Huai Nan Zi Zhen Xun pointed out: "There are those who have a beginning, those who have a beginning without a beginning, and those who have a husband without a beginning without a beginning." It is believed that the world has its opening time, its pre-opening period and its pre-opening period. Huai Nan Zi Tian 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 heaven and earth. In ancient Greece, there were similar opinions. Leucippus, for example, suggested that the light matter escapes to the outer void due to the swirling motion of atoms in the empty space, while the rest of the matter constitutes a spherical celestial body, 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 put forward the vortex theory of the origin of the solar system; In 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. In 1755 and 1796, Kant and Laplace respectively put forward the theory of the origin of the solar system. The modern theory of new nebula to explore the origin of the solar system Z is developed on the basis of Kant-Laplace's theory of nebula.
in p>1911, e. hertzsprung established the first color magnitude map of galaxy clusters; In 1913, H.N. Russell drew the spectrum-luminosity diagram of the stars, that is, the Herro diagram. After obtaining this map, Russell put forward a star evolution theory that a star starts from a red giant, first shrinks into the main sequence, then slides down along the main sequence, and finally becomes a red dwarf. In 1924, A.S. Eddington proposed the mass-luminosity relation of stars; From 1937 to 1939, C.F. weizsacker and Bert 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 a scientific theory of stellar evolution. The study of the origin of galaxies started late. At present, it is generally believed that it evolved from the original galaxies in the late stage of the formation of our universe.
in p>1917, a. Einstein established a "static, finite and unbounded" model of the universe by applying his newly founded general theory of relativity, which laid the foundation of modern cosmology. In 1922, G.D. Friedman discovered that according to Einstein's field equation, the universe is not necessarily static, it can be expanded or oscillated. The former corresponds to the open universe, while the latter corresponds to the closed universe. In 1927, G. Lemaitre also proposed an expanding universe model. In 1929, Hubble discovered that the redshift of a galaxy is directly proportional to its distance, and established the famous Hubble law. This discovery is a strong support for the expanding universe model. In the mid-2th century, G Gamov and others put forward the cosmological model of thermal big bang, and they also predicted that according to this model, we should be able to observe the low-temperature background radiation in space. The discovery of microwave background radiation in 1965 confirmed the prediction of Gamov and others. Since then, many people regard the Big Bang universe model as the standard universe model. In 198, Gus of the United States further proposed the skyrocketing universe model on the basis of the thermal 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 nine planets in the solar system: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto. Except Mercury and Venus, all other planets have satellites orbiting them. The earth has one satellite-the moon, and Saturn has 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 1.4 million kilometers, and the largest planet Jupiter has a diameter of about 14, kilometers. The size of the solar system is about 12 billion kilometers. There is evidence that there are other planetary systems outside our solar system. 25 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 a oblate space, which looks like a discus from the side, but from the front? It is in a vortex shape. The diameter of the Milky Way is about 1, light years, and the sun is located in a spiral arm of the Milky Way, about 3, light years away from the galactic center. There are many similar celestial systems outside the Milky Way, called extragalactic galaxies, which are often referred to as galaxies. About 1 billion have been observed. Galaxies also gather into large and small groups called galaxy clusters. On average, there are more than 1 galaxies in each cluster, with a diameter of tens of millions of light years. Tens of thousands of galaxy clusters have been discovered. A small cluster of galaxies consisting of about 4 galaxies, including the Milky Way, is called the local cluster. A number of galaxy clusters gather together to form a larger and higher-level celestial system called supercluster. Supercluster often has a flat shape, and its long diameter can reach hundreds of millions of light years. Usually, supercluster contains only a few clusters, and only a few supercluster have dozens of clusters. The supercluster consisting of the local cluster and about 5 nearby clusters is called local supercluster. At present, the astronomical observation range has been extended to the vast space of 2 billion light years, which is called the total galaxy.
the diversity of celestial bodies is very different, and the matter in the universe is varied. Among the celestial bodies in the solar system, the surface temperature of Mercury and Venus is about 7K, and the temperature of distant Pluto towards the sun is only 5 K at the highest. The surface of Venus is covered with dense carbon dioxide atmosphere and sulfuric acid cloud, and the air pressure is about 5 atmospheres, while the surface atmosphere of Mercury and Mars is extremely thin, and the atmospheric pressure of Mercury is even less than 2×1-9 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 .7g/cm3, which is smaller than that of water; the average density of Jupiter, Uranus and Neptune is slightly larger 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 has been found that some red giant stars are thousands of times the diameter of the sun. Neutron stars are only a few tens of thousands of times the diameter of the sun; The luminosity of Supergiant star is as high as millions of times that of the sun, but the luminosity of white dwarfs is less than a few 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 as 1, times and 1 billion times that of water respectively. The surface temperature of the sun is about 6K, the surface temperature of O-star is 3K, and the surface temperature of infrared star is only about 6 K.. The average magnetic field intensity of the sun is 1×1-4 Tesla, and the magnetic fields of some magnetic white dwarfs are usually thousands or tens of thousands of gauss (1 gauss = 1-4 Tesla), while the magnetic field intensity of pulsars can be as high as 1 trillion gauss. Some stars have basically the same luminosity, while others are constantly changing, which is called variable stars. Some variable stars have periodic luminosity changes, ranging from one hour to several hundred days. The luminosity changes of some variable stars are sudden, 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 often gather into binary stars or clusters of stars, which may account for 1/3 of the total number of stars. There are also clusters of dozens, hundreds or even hundreds of thousands of stars. Cosmic matter not only forms stars and planets in dense form, but also forms interstellar matter in 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 and nebulae that emit visible light, there are also ultraviolet celestial bodies, infrared celestial bodies, X-ray sources, gamma-ray sources and radio sources in the universe.
galaxies can be divided into elliptical galaxies, spiral galaxies, rod-spiral galaxies, lens galaxies and irregular galaxies. In the 196s, many extragalactic celestial bodies were discovered, which were experiencing explosion or throwing huge amounts of matter, and were collectively called active galaxies, including various radio galaxies, Seyfert galaxies, N-type galaxies, Makaryan galaxies, Buthus BL-type celestial bodies, 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 155 Joules, massive mass and particle ejection, intense light change and so on. 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 and so on. It provides an ideal experimental environment for us to understand the objective material world.
Motion and development The celestial bodies in the universe are in perpetual motion and development, and the motion forms of celestial bodies are various, such as rotation, their own space motion (local motion), revolution around the center of the system and participation in the whole process.