Astronomical history

The origin of astronomy can be traced back to the embryonic era of human culture. In ancient times, in order to indicate the direction and determine the time and season, people observed the sun, the moon and the stars, determined their positions, found out their changing laws, and compiled calendars accordingly. From this perspective, astronomy is one of the oldest natural science disciplines.

In ancient times, people determined the time and direction by observing the sun, moon and stars with naked eyes, worked out calendars and guided agricultural production, which was the earliest beginning of astrometry. The content of early astronomy is essentially astrometry. Since Heliocentrism was proposed by Copernicus in the middle of16th century, the development of astronomy has entered a new stage. Previously, natural sciences, including astronomy, were severely bound by religious theology. Copernicus's theory liberated astronomy from the bondage of religion, and in the next century and a half, it developed from classical astrometry, which mainly described the position and motion of celestial bodies, to celestial mechanics, which sought the mechanical mechanism that caused this motion.

18 and 19 century, classical celestial mechanics reached its peak. At the same time, due to the wide application of sub-optics, geodesy and photography, astronomy began to develop in the direction of in-depth study of the physical structure and process of celestial bodies, and astrophysics was born.

Modern physics and technology developed rapidly in the 20th century, and found a wide range of applications in astronomical observation and research, making astrophysics the mainstream discipline in astronomy, and at the same time promoting the new development of classical astromechanics and astrometry. People's understanding of the universe and various celestial bodies and astronomical phenomena in the universe has reached an unprecedented depth and breadth.

Astronomy is essentially an observational science. All discoveries and research achievements in astronomy are inseparable from astronomical observation tools-telescopes and their back-end receiving equipment. Before the17th century, people had made many astronomical observation instruments, such as China's armillary sphere and simple instruments, but the observation work could only rely on the naked eye. 1608, the Dutchman Liporsay invented the telescope. 1609, Galileo made the first astronomical telescope and made many important discoveries. Since then, astronomy has entered the era of using telescopes. Since then, people have continuously improved the performance of telescopes in order to observe darker celestial bodies and obtain higher resolution. 1932, Jansky, an American, observed radio waves from celestial bodies with his rotating antenna array, which initiated radio astronomy. The first parabolic reflector radio telescope was born in 1937. After that, with the continuous expansion and improvement of the performance of radio telescope in terms of aperture, receiving wavelength and sensitivity, radio astronomical observation technology has made important contributions to the development of astronomy. In the last 50 years of the 20th century, with the development of detectors and space technology and the deepening of research work, astronomical observation has further expanded from visible light and radio bands to electromagnetic wave bands including infrared, ultraviolet, X-ray and γ-ray, forming multi-band astronomy, which provides a powerful observation means for exploring the physical essence and astronomical phenomena of various celestial bodies, and astronomy has developed to a brand-new stage. As for the receiving equipment at the back end of the telescope,1In the mid-9th century, photography, spectroscopy and photometry were widely used in astronomical observation, which greatly promoted the exploration of the movement, structure, chemical composition and physical state of celestial bodies. It can be said that astrophysics has gradually developed into the mainstream discipline of astronomy after these technologies have been applied.

Humans have long wanted to swim in space. 1903, mankind opened up the first moon park on earth. You can board a winged car in the shape of a cigar for 50 cents, then the car body shakes violently, and finally board a moon model.

In the same year, the Wright brothers crashed in the air for 59 seconds, and a self-taught Russian named Konstantin Ziolkowski published an article entitled "Exploring Space with Reaction Instruments". In his article, he calculated that the missile must fly at a speed of10.8 million miles per hour to overcome the gravity of the earth. He also suggested building a liquid-driven multistage rocket.

In the 1950s, there was an accepted basic view that which country successfully established the permanent space station first would control the whole earth sooner or later. Wernher wernher von braun described intercontinental missiles, submarine missiles, space mirrors and possible trips to the moon to Americans. He once envisaged the establishment of a space station with frequent manned and capable of launching nuclear missiles. He said: "If we consider that the space station flies over all inhabited areas on the earth, then people can realize that this nuclear war technology will give satellite manufacturers an absolute advantage in the war.

196 1 year, Gagarin became the first man to go into space. Russians use him to show that it is not angels or God flying around in the sky. John F. Kennedy's campaign slogan in the United States is "New Frontier". He explained: "We are once again living in an era full of discovery. Space is our inestimable new frontier. " For Kennedy, the Soviet Union's first entry into space was "the most painful failure that the United States has experienced for many years". The only way out is attack and defense. 1958, the United States established the National Aeronautics and Space Administration, and launched the first satellite "Explorer" in the same year. 1962, john glenn became the first American to enter Earth orbit.

Many scientists are skeptical about the dangerous manned space flight, and they prefer to explore the solar system by plane.

At that time, Americans achieved a breakthrough: three astronauts flew around the moon in the Apollo spacecraft. In this context, the first docking of two manned spacecraft scheduled for June 1969+ 10 is of special significance.

In 1980s, the third generation space station "Peace" of the Soviet Union reached the peak of its space activities, which made Americans feel jealous. The "Peace", known as the "Artificial Tiangong", was launched on1February 20th, 986. It is the only manned space orbital station that can run in near-earth space for a long time. The cabins corresponding to quantum 1, quantum 2, crystal, spectrum and nature form a huge space orbit complex with a weight of 140 tons and a working volume of 400 cubic meters. There are 106 Russian and foreign astronauts who have been inspected in this "small space factory", with as many as 22,000 scientific research projects and 600 key projects.

The most attractive experiment carried out on the "Peace" is to prolong people's stay in space. Prolonging people's stay in space is the most crucial step for people to fly out of the cradle earth and March into Mars and other celestial bodies. To solve this problem, we need to overcome weightlessness, cosmic radiation and psychological obstacles caused by people in space. Russian astronauts have made great progress in this respect, among which astronaut poliakov created a record of 438 days of continuous flight of "Peace", which cannot but be regarded as an important achievement in the history of space flight in the 20th century. A large number of life science experiments such as cultivating quail, salamander and planting wheat were carried out on the orbital station.

If the Mir space station is regarded as the third generation space station, the International Space Station belongs to the fourth generation space station. The International Space Station (ISS) project costs more than 60 billion US dollars, and it is the largest manned spaceflight project of mankind to date. From the initial conception to the final implementation, it is not only the product of the competition between the United States and the Soviet Union, but also the result of the current cooperation between the United States and Russia, which reflects a historical process from the side.

The implementation of the International Space Station program is divided into three stages. The first phase from 1994 has been completed. During this period, the United States and Russia mainly carried out a series of joint manned space activities. The American space shuttle docked with the Russian "Peace" orbital station eight times and flew together, which exercised the ability of American astronauts to live and work in the space station. The second stage started from June1998+065438+1October: Russia put the main cabin of the space station, the functional cargo cabin, into orbit with a proton -K rocket. It also undertakes some military experiments, so the cabin is only allowed to be used by American astronauts. The launch and docking of the experimental module will mark the end of the second phase, when the space station has begun to take shape and can accommodate three astronauts for a long time; The third stage is to send the living module of the United States, the experimental module made by the European Space Agency and Japan, and the mobile service system of Canada into space. When these modules are docked with the space station, it marks the final completion of the assembly of the International Space Station. At this time, the number of astronauts on the space station can be increased to seven.

The United States, Russia and other countries 15 jointly build the International Space Station, which indicates that an era of joint exploration and peaceful development of space with other countries is coming. However, the achievements of manned space activities for decades are far from satisfying their desire for space. "The road is long and Xiu Yuan is awkward, and I will search up and down." Humans have always had the desire to conquer space and the determination to use space resources peacefully. 1998165438+10 In October, Glenn, the 77-year-old American astronaut who entered Earth orbit, once again set foot on a trip to space with his unswerving ambition, as if to tell mankind that conquering space at such a speed is not a dream.

[Edit this paragraph] Overview of astronomy

Astronomy differs from meteorology. Its research object is the nature of various celestial bodies outside the earth's atmosphere and various phenomena occurring on celestial bodies-astronomical phenomena, while the research object of meteorology is various phenomena occurring in the earth's atmosphere-meteorology.

Astronomy studies all kinds of celestial bodies in space, ranging from the moon, the sun, planets, stars, galaxies outside the Milky Way to the whole universe, to asteroids, meteoroids, and even large and small dust particles distributed in the vast space. Astronomers call all these objects celestial bodies. The earth is also a celestial body, but astronomy only studies the general properties of the earth and generally does not discuss its details. In addition, the motion properties of artificial aircraft such as satellites, spaceships and space stations also belong to the research scope of astronomy and can be called artificial celestial bodies.

The celestial bodies in the universe can be divided into several levels from near to far: (1) Solar system celestial bodies: including the sun, planets (including the earth), satellites of planets (including the moon), asteroids, comets, meteoroids and interplanetary media. (2) Various stars and clusters in the Milky Way: including variable stars, binary stars, multi-stars, clusters, nebulae and interstellar media. (3) Extragalactic galaxies, referred to as galaxies for short, refer to huge star systems similar to ours located outside our Milky Way galaxy, as well as large celestial bodies composed of galaxies, such as binary galaxies, multi-galaxies, galaxy clusters, supercluster clusters, etc. In addition, there are intergalactic media distributed between galaxies.

Astronomy also explores the origin, structure, evolution and future outcome of the universe as a whole, which is the research content of cosmology, a branch of astronomy. Astronomy can also be divided into astrometry, celestial mechanics and astrophysics according to the content of research.

Astronomy is always the forerunner of philosophy and always at the forefront of debate. As a basic research discipline, astronomy is closely related to human society in many aspects. The strict law of time, the alternation of day and night, and the change of seasons must be determined by astronomical methods. Mankind has entered the space age, and astronomy plays an irreplaceable role in the success of various space explorations. Astronomy has also made its own contribution to the disaster prevention and mitigation of human beings and the earth. Astronomers will also pay close attention to catastrophic astronomical events, such as the possibility that comets may collide with the earth, prevent them in time and make corresponding countermeasures.

[Edit this paragraph] Solar system

(Note: In the resolution No.5 adopted by the 26th International Astronomical Union held in Prague on August 24th, 2006, Pluto was listed as a dwarf planet, named asteroid 134340, and was eliminated from the nine planets in the solar system. So now there are only eight planets in the solar system. All the references to "nine planets" in this article have been changed to "eight planets". )

The solar system consists of the sun, eight planets, 66 satellites and countless asteroids, comets and meteorites.

The order of planets from the sun is: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.

Mercury, Venus, Earth and Mars near the sun are called terrestrial planets. Spacecraft have all detected and landed on Mars and Venus, and achieved important results. They are characterized by high density (greater than 3.0g/cm3), small volume, slow rotation and few satellites. They are mainly composed of stone and iron, with silicate inside and firm shell.

Jupiter, Saturn, Uranus and Neptune, which are far away from the sun, are called woody planets. The spacecraft also detected them, but they didn't land. They all have a thick atmosphere, mainly composed of hydrogen, helium, ice, methane, ammonia and so on. Their mass and radius are much larger than that of the earth, but their density is low and their surface features are difficult to understand. Generally speaking, they all have solid cores similar to terrestrial planets.

There are more than 100000 asteroids (that is, irregular small stars composed of rocks) between Mars and Jupiter. It is speculated that they may be formed by fragments of a planet between Mars and Jupiter, or some rock fragments failed to accumulate into a unified planet. Meteorites exist between planets and are made of stone or iron.

Star, distance (AU), radius (Earth), mass (Earth), orbital inclination (degrees), orbital eccentricity, inclination and density (g/cm3).

Sun, 0,109,332,800,-,-,-,1.4 10.

Water Star, 0.39, 0.38, 0.05, 7, 0.2056, 0. 1, 5.43.

Venus, 0.72, 0.95, 0.89, 3.394, 0.0068, 177.4, 5.25.

Earth, 1.0, 1.00, 1.00, 0.000, 0.0 167, 23.45, 5.52.

Mars, 1.5, 0.53, 0. 1 1 .850, 0.0934, 25. 19, 3.95.

Mu Xing, 5.2,11.0,318, 1.308, 0.0483,3.12, 1.33.

Earth satellites, 9.5, 9.5, 95, 2.488, 0.0560, 26.73, 0.69.

Uranus, 19.2, 4.0, 17, 0.774, 0.04 1, 97.86, 1.29.

Neptune, 30. 1, 3.9, 17, 1.774, 0.0097, 29.56, 1.64.

The distance between the planet and the sun is regular, that is, the distance between the planet and the sun (represented by a) is a=0.4+0.3*2n-2 (astronomical unit), where n represents the nth planet from near to far (see the above table for details). The rotation period of the Earth, Mars, Jupiter, Saturn, Uranus and Neptune is about 12 hour to one day. Except Mercury and Venus, all other planets have satellites orbiting them, forming a satellite system.

In the solar system, more than 1600 comets have been found, about half of which revolve around the sun in the same direction and the other half in the opposite direction. Comets will have strange shape changes when they orbit the sun. There are also a large number of meteoroids, large and small, in the solar system, some of which are in groups and are the products of the disintegration of comets. Large meteoroids fall to the ground and become meteorites. The solar system is a tiny part of the Milky Way, and the sun is just one of the hundreds of billions of stars in the Milky Way, which is about 8,500 parsec, or less than 30,000 light years. The sun takes the whole solar system around the center of the Milky Way. Visible, the solar system is not in the center of the universe, nor in the center of the Milky Way. The sun was formed by the collapse of a small piece of interstellar cloud 5 billion years ago, and its life span is about 65.438+0 billion years.

[Edit this paragraph] Space flight

The universe is the general name of the vast space and all kinds of celestial bodies and dispersed substances existing in it. The universe is a material world, which is in constant movement and development. For thousands of years, scientists have been exploring when and how the universe was formed. Until today, scientists are convinced that the universe was formed by a big bang about 654.38+0.5 billion years ago. Before the explosion, all the matter and energy in the universe gathered together and condensed into a very small volume with extremely high temperature and density, and then a big explosion occurred. The big bang dispersed the matter, expanded the space and lowered the temperature accordingly. Later, all the galaxies, stars, planets and even life in the universe were gradually formed in this process of continuous expansion and cooling. However, the theory that the Big Bang produced the universe cannot accurately explain what existed before "stored matter and energy gathered at one point". The Big Bang theory was founded by Gamov in 1946.

Big bang theory

Big Bang Cosmology is the most influential theory in modern cosmology, also known as Big Bang Cosmology. Compared with other models of the universe, it can explain more observational facts. Its main point is that our universe once had an evolutionary history from hot to cold. During this period, the cosmic system is not static, but constantly expanding, which makes the density of matter evolve from dense to sparse. This process from hot to cold, from dense to thin, is like a huge explosion. According to BIGBANG's cosmology, the whole process of BIGBANG was in the early universe, and the temperature was extremely high, above 1000 billion degrees. The density of matter is also quite large, and the whole universe system is in equilibrium. There are only some elementary particles in the universe, such as neutrons, protons, electrons, photons and neutrinos. But because the whole system is expanding, the temperature drops rapidly. When the temperature drops to about1000 billion degrees, neutrons begin to lose the condition of free existence, and they either decay or combine with protons to form heavy hydrogen, helium and other elements. It was from this period that chemical elements began to form. When the temperature further drops to 6.5438+0 million degrees, the early process of forming chemical elements ends (see the theory of element synthesis). The substances in the universe are mainly protons, electrons, photons and some lighter nuclei. When the temperature drops to several thousand degrees, the radiation decreases, and the universe is mainly gaseous. Gas gradually condenses into gas clouds, and then further forms various star systems, becoming the universe we see today. The Big Bang model can uniformly explain the following observations:

(1) According to the Big Bang theory, all stars were born after the temperature dropped, so the age of any celestial body should be shorter than the period when the temperature dropped to today, that is, less than 20 billion years. The measurement of the ages of various celestial bodies proves this.

(2) It is observed that the celestial bodies outside the river have a systematic red shift of spectral lines, and the red shift is roughly proportional to the distance. If it is explained by Doppler effect, then the red shift is a reflection of the expansion of the universe.

(3) Helium is abundant in various celestial bodies, most of which are 30%. The mechanism of stellar nuclear reaction is not enough to explain why there is so much helium. According to the big bang theory, the early temperature was very high and the efficiency of producing helium was also very high, which can explain this fact.

(4) According to the expansion speed and helium abundance of the universe, we can calculate the temperature of the universe in each historical period. Gamov, one of the founders of the Big Bang theory, predicted that today's universe is already very cold, and the absolute temperature is only a few degrees. 1965 detected microwave background radiation with thermal radiation spectrum in microwave band, and the temperature was about 3K.