Manuscript about that moon (figure)

It took mankind a long time to realize that the earth under our feet is a sphere. Where should the globe of the earth be placed in the universe? At first people put it at the center of the universe. Later, a man named Parado Xi found that some stars in the sky were moving-people called them planets, and correspondingly, the static stars were called stars. So people say that the moon, the sun, the planets and all the stars in the sky are in circular orbits around the earth. Ptolemy was the first to determine the relationship between the earth and the planets by mathematical methods, and made a quantitative description of the universe in the eyes of the ancient Greeks. This picture later became the theoretical basis of Christian theology. It was not until 1543 that Copernicus published the theory of celestial motion that the earth was moved away from the center of the universe. In Copernicus's system, the earth is no longer the center of the universe, but revolves around the sun in a circular orbit like other planets.

/kloc-before the 0 th/7 th century, people always observed elephants with the naked eye and studied celestial bodies with some simple measuring instruments, mainly the sun, the moon and the five planets visible to the naked eye. China people used the familiar five elements of fire, water and earth in Jin Mu, and the ancient Greeks and Romans named these planets after their familiar gods. 16 10 years, Galileo invented the astronomical telescope, which broadened people's horizons and saw a new picture of the universe invisible to the naked eye.

From18th century to the first half of19th century, modern astronomy has made great progress. During this period, a complete motion theory of planets, the earth and comets was established, some new planets, satellites of planets and asteroids were discovered, and the observation field was extended from the solar system to other star systems in the Milky Way. /kloc-in the second half of the 9th century, astronomers introduced some new theories and methods in physics at that time into the study of celestial bodies, founded astrophysics, and began the stage of modern astronomy.

After entering the 20th century, great progress has been made in both astrophysical theory and celestial observation methods. In the field of traditional optical astronomy, with the appearance of reflective astronomical telescope, the aperture of astronomical telescope is increasing, which changes the limitations of refractive astronomical telescope in19th century. In 1908, 1.5m mirror, 19 18, 2.5m mirror, 1948, 6m mirror, 1976 and 1993.

1932, American engineer Jansky discovered the cosmic radio waves from the center of the Milky Way galaxy, which were later called cosmic rays, thus finding a new way to understand the universe and establishing radio astronomy. The improvement of means is the premise of the development of astronomy. The appearance of radio telescope makes the universe appear in the whole range of human vision, and makes people know some celestial bodies and substances that cannot be understood according to visible light, such as supernova remnants, quasars, pulsars, interstellar molecules, microwave background radiation and so on.

Since the 1960s, the foothold of human exploration of the universe is no longer limited to the earth. 1962, American sounding rockets flew away from the earth 150 kilometers with X-ray detectors, and found strong X-rays from the universe that could not be received on the earth's surface, which ushered in the era of space astronomy. 1in June, 1998, the American space shuttle Discovery carried an alpha magnetic spectrometer developed by scientists in China, trying to find antimatter in the universe.

2. The structure of the universe

● Cascade distribution and isotropy

The universe is the biggest research object of natural science, and human beings have gained more and more knowledge about the universe. This knowledge contains what is necessary for scientific explanation and model of the universe. It enables us to rationally infer the origin of the universe and the future of the universe in a not-too-distant period within a measurable range; Enable us to launch Earth satellites and inter-day detectors for various purposes; So that we can find the companion of intelligent life in the universe in a scientific and technological way. ...

Our basic understanding of the universe now is that in a relatively small space-time, the matter in the universe gathers into stars, galaxies, galaxy clusters, superclusters and superclusters. As a whole, the universe is homogeneous and isotropic. The universe has no center, and observers of any typical galaxy see the same laws of the universe.

● The universe is expanding on a large scale.

People find that there are many celestial bodies like clouds in the sky, which we call nebulae. 1924, Hubble aimed the telescope at the Andromeda nebula and distinguished the individual stars that make up the nebula, thus distinguishing the extragalactic galaxy from the dust cloud, and found that the Andromeda nebula is not a celestial body in the Milky Way, but a galaxy about 2.2 million light years away from the Earth, called the extragalactic galaxy. Then he made a more in-depth and detailed study of the extragalactic nebula and found many more distant galaxies.

Starting from 19 12, Slipher, an American astronomer who devoted himself to the study of celestial spectra, found that almost all the spectral lines of extragalactic galaxies moved to the red end. According to the Doppler effect, this means that these galaxies are far away from the earth and running at a fairly high speed. For example, the speed of the Virgo Nebula is 1000 km per second. During the period of 1929, Hubble inspected Slipher's work, and combined with his own research on extragalactic galaxies, he expanded the research scope of running speed to 20,000 kilometers per second, and put forward the famous Hubble law: the red shift of the spectral lines of galaxies is proportional to their distance from the Earth. Subsequent observations further confirmed Hubble's theory. That is to say, the redshift of galaxies outside the river is a systematic redshift reflecting the overall characteristics of the universe-from any point in the universe, almost all celestial bodies can be seen leaving that point-the universe is expanding. This is an all-round centerless expansion, similar to the situation where the points on an inflated balloon are far apart.

● The space-time of the universe is flexible.

In Newton's view of time and space, space is three-dimensional straight, absolutely uniform and isotropic; Time is one-way and one-dimensional, flowing at a constant speed like a river. Time and space have nothing to do with matter, they are like containers of matter, which will exist forever and will never change.

Einstein put forward special relativity and general relativity in 1905 and 19 15 respectively. The special theory of relativity initially established the unity of time and space and the relationship between time and space and material movement. In the special theory of relativity, the space-time metric changes with the motion of matter.

General relativity unifies gravitational mass and inertial mass, and the gravitational field is equivalent to a frame of reference with considerable acceleration. He also revealed the unified relationship between four-dimensional space-time and matter, pointing out that space cannot exist independently without matter for a period of time, and the quality and distribution of matter determine the structure of space-time. Conversely, the gravitational field is the expression of spatial geometric curvature, and spatial curvature reflects the strength of the gravitational field.

According to Einstein's theory, some people infer that in a strong gravitational field, such as a black hole, space shrinks to 1 dimension and time expands to 3 dimensions; Super-strength theory holds that in an extremely microscopic and high-energy world, space-time may be 1 1 dimension.

Einstein pointed out that the curvature of space can be measured around the gravitational field, and predicted that observing the position of stars in the solar background during the total solar eclipse could confirm this phenomenon. 19 19 Eddington led a team to Africa to observe the total solar eclipse, which confirmed Einstein's prediction that light bends in the gravitational field, which also confirmed Einstein's theory about the relationship between matter and space-time structure.

3. Solar system

So far, the solar system is still the celestial system that we know the most about in the universe. For centuries after Copernicus, the solar system has been the focus of astronomical research. By the end of 19, scientists have discovered eight other planets and nearly 500 asteroids besides Pluto. In the 1920s and 1930s, astronomers discovered Pluto, a new big planet in the solar system, and found some satellites, more than 7,000 asteroids and several comets around the big planet, thus drawing a more complete picture of the solar system.

● Sun

The sun is the celestial body most closely related to human life. Everything grows with the sun, and almost all the energy we live on the ground comes from the sun. However, due to the limitation of research methods, it was not until the 20th century, with the development of physics and astronomy, the advent of more sophisticated instruments, especially the launch of solar space detectors, that human beings had a deep understanding of the sun.

Now we know that the sun is a gas ball, the main component is hydrogen, and the energy of the sun comes from the nuclear fusion of its own hydrogen atoms; The average surface temperature of the sun is five or six thousand degrees, and the central temperature reaches tens of millions of degrees; The sun radiates enormous energy all the time, and only a tiny part of it radiates to the earth; The sun is both the source of life and a huge killer. Because of its strong magnetic field, extremely high internal temperature and intense nuclear reaction, various interaction mechanisms in nature work at any time, and the powerful solar wind composed of high-frequency electromagnetic waves such as ultraviolet rays and X-rays and various particle streams hangs over the earth.

The solar wind is an important source of cosmic rays carried by the earth. If cosmic rays March in, there will never be life on the earth. What protects us is the earth's atmosphere, especially the ozone layer, and the powerful earth's magnetic field. That's why we are worried about the ozone holes in the Antarctic and Arctic today and strongly advocate the protection of the ozone layer. The life span of the sun is about 654.38+00 billion years, and now it has covered about half the distance.

● Moon

The moon is the satellite of the earth and the nearest celestial body. Its dazzling appearance, visible to the naked eye, once entrusted countless beautiful wishes of mankind.

17th century After Galileo aimed his telescope at the moon and saw the crater for the first time, people didn't gradually understand the physical characteristics of the moon until the 20th century. In the 1920s, French scientist Leo speculated that there was a layer of dusty soil composed of volcanic ash on the surface of the moon. At the end of 1950s, the first space exploration was aimed at the moon. 1959, the former Soviet Union launched the first lunar probe, and the photos sent back made people see the back of the moon for the first time. Soon, the United States also launched a series of lunar probes. 1On July 20th, 972, American Apollo spacecraft 1 1 landed on the moon, and astronaut Armstrong became the first man to land on the moon. Up to now, 12 people have landed on the moon six times.

Now we know that the moon is a dead body. It has no atmosphere, no water, no active volcano and basically no "geological movement". It has basically ended its astronomical evolution except quietly rotating around the earth and receiving all kinds of impacts and radiation from space. Perhaps only humans can give the moon new life.

There are three main theories about the origin of the moon: one thinks that the moon was formed at the same time as the earth during its birth, which was the result of the disturbance and accumulation on the disk when the early earth embryo was in the accretion disk stage; Another view is that the origin of the moon is much later than that of the earth. The moon was thrown from the earth, and the Pacific Ocean is the trace left by the moon after it left the earth. The third view is that the moon is an asteroid plundered by the earth. But all three theories have unclear explanations, so the origin of the moon is still an unsolved mystery.

At present, some countries, including China, have their own aspirations or have made plans to explore and develop the moon. I'm afraid the first foothold of human space in the future will be the moon.

● Planets

Before the establishment of astrophysics in the second half of the19th century, the sun and planets, comets and satellites in the solar system were always the focus of astronomers' research. With the advent of the space shuttle, humans can observe some big planets at close range. Since the 1960s, the United States, the Soviet Union, Germany and other countries have launched many interstellar probes, which are mainly used for scientific investigation of celestial bodies in the solar system such as Mars, Venus and Mercury. Among them, American Mars probes Viking 1 and Viking 2 landed on Mars in 1975; 1997, the American Mars probe Pathfinder landed on Mars again to further explore the terrain of Mars and make an in-depth investigation for the future landing of mankind on Mars. Since 1970s, some planetary probes have flown to the outer solar system to investigate Jupiter, Saturn, Uranus and Neptune.

Mars is the planet that humans know the most so far, and it is also the solar system celestial body with various astronomical and geological conditions closest to the Earth. Mankind dreams of transforming Mars by various physical, chemical and biological methods, so that it will present conditions suitable for human habitation in the near future, so as to settle on Mars when mankind walks out of the cradle of human childhood and takes the first step of emigrating to space.

In addition to the nine planets, there is a strange asteroid belt between Mars and Jupiter in the solar system. The initial discovery of asteroids is due to people's confusion-the distance between each planet and the sun in the solar system is about 1.3 ~ 2.0 times that of the previous one, with the only exception that the distance between Jupiter, the fifth planet, and the sun is about 3.4 times that of Mars, the fourth planet. German astronomers, inspired by the discovery of Uranus by theoretical deduction, thought that there should be another planet between Mars and Jupiter, and organized a team to look for it. However, the first asteroid was discovered by accident by Italian astronomer Piazi. 180 1 year 1 month 1 day, Piaz found a dim celestial body between Mars and Jupiter that changed its position every day. German mathematician Gauss calculated its orbit in the space where people expected to find new planets, proving that it was a planet, and Piaget named it Ceres. However, Ceres is too small, with a radius of only 1 1,000 kilometers, only150 the size of the moon, which seems to be insufficient to fill the gap between Mars and Jupiter, so astronomers continue to search. 1807, Olbers discovered three new planets in this space, named Pallas Athena, Poseidon and Vesta respectively. Astronomer Herschel suggested calling these planets asteroids, and the term was extended.

So far, thousands of asteroids have been found in this space between Mars and Jupiter, so people call it the asteroid belt. It is generally believed that this asteroid belt is the result of the same perturbation of the strong gravity of Jupiter, the largest planet in the solar system, and the gravity of Mars. This disturbance makes it difficult for the matter in the asteroid belt to gather into planetesimals, so it is not a big planet.

In addition to the asteroids in the asteroid belt, there are some asteroids distributed in the orbits of other planets in the solar system, or have their own independent orbits. The orbital curvature of these asteroids is often extremely large, that is to say, they are extremely flat, extremely long, extremely far from the perihelion, and extremely close to the perihelion, and intersect with the orbits of other planets such as the Earth. Astronomers say its perigee is closer to Earth than Venus. Intersecting with the orbit of the planet can reach a fairly close distance. On the one hand, asteroids may be plundered by the planet and become satellites of the planet; On the other hand, although it is extremely unlikely, once it happens, it will be a disaster-asteroids may collide with big planets, and of course, the most worrying thing is to collide with our earth. This is also an important reason why human beings must find more shelters in the universe. Carl sagan, a famous popular science writer, once quoted a western proverb to explain this truth: "We can't put all our eggs in the same basket."

● Satellite

The moon is the only satellite on the earth and the only satellite in the solar system that humans didn't know until modern times. Therefore, since ancient times, people have regarded it as the same as Jin Mu, water, fire, earth and other planets, without realizing its difference from other planets. 16 10, Galileo observed the sky with a self-made telescope and found four moons of Jupiter. This incident caused an uproar at that time, because it meant that not only the earth was not the center of the universe, but also the sun was not the only center of the universe. Such a conclusion was absolutely intolerable by the "orthodox thinking" at that time. Now, humans have discovered at least 64 satellites in the solar system; And know that Titan has an atmosphere, which is the only satellite known to have an atmosphere. Atmosphere is a serious matter. Because of the atmosphere, there is the possibility of re-globalization, and any place where globalization is possible may become the future home of mankind.

● Comet

For a long time, the appearance of comets has been regarded as an ominous sign in both the East and the West. For westerners, this situation has completely changed in 1682. This year, Newton's friend Harley found that the comet that appeared in that year had once entered human vision. He calculated that this comet would come again every 76 years. 1758, this comet really came. However, people still don't know why the shape of comets will change after running in the solar system for a long time. It was not until the 20th century that people knew that comets are celestial bodies orbiting the sun in elliptical orbits, but their orbits are much flatter than those of planets, so perihelion is often very close, but apohelion is far away.

Comets are mainly composed of snow and dust. Some people vividly say that comets are "dirty snowballs". When the comet is far away from the sun, it is in a completely solid state. When it is close to the sun, it will form water vapor and dust due to heat. So its shape changes greatly, it will expand obviously, and in most cases it will pull out a long or short tail. We also know that comets lose some substances every time they pass near the sun. After several passes through the sun, they all disappear due to evaporation and decomposition into dust, or leave a core made of rocks.

The origin of comets is still an unsolved mystery.

4. Galaxy

The Milky Way is a celestial system with hundreds of billions of stars and a lot of interstellar matter, and the sun is an extremely ordinary medium-sized star in the Milky Way. The silvery white band we see in the clear sky on a summer night is the projection of the Milky Way on the celestial sphere, and the shining white is the brilliance of dense stars.

If you look at the Milky Way from the outside, it should be a discus-shaped galaxy with a spiral structure. The diameter of the disk of the Milky Way is about 654.38+ million light years, the diameter of the nuclear sphere is about 654.38+ million light years, and the diameter of the silver core is about 3 light years. Our sun is on a spiral arm of the Milky Way, about 40,000 light years away from the center of the Milky Way. So when you look at the Milky Way on the earth, the side facing the silver heart is dense and bright, and the other side is sparse and dim. There are relatively dense stars in the silver disk, especially some relatively young or even forming stars, open clusters, interstellar media and gas nebulae on spiral arms; Old globular clusters are distributed in silver halos; There is a huge black hole in the center of the huge silver core. The total mass of the Milky Way is 65.438+04 billion solar mass, of which 90% are stars and 654.38+00% are interstellar media composed of gas and dust. The whole galaxy rotates around an axis perpendicular to the silver disk, and the sun rotates at a speed of 220 kilometers per second.

5. Evolution of stars

The ancients divided the stars in the sky into planets and stars. The former has obvious movement, while the latter does not move. 17 18, astronomer Harley found that the positions of the three brightest stars-Sirius, Nanhesan and arcturus-were very different from those recorded by astronomers in the Greek era, and could not be normal errors, so he concluded that these stars were not stationary, but moving quite slowly, because they were quite far away from us, so they seemed to be stationary. /kloc-in the 0/9th century, people found that stars in the universe have different spectra, so some people asked whether stars also evolved. The answer to this question was not found until the 1950s. During this period, American astronomer Schwarzenegger combined the energy and structure of stars with the evolution of stars through systematic research. Huo Yier gave a scientific explanation for the evolution of stars, and divided the life cycle of stars into several stages, such as origin, main sequence star, red giant star and dwarf star. Among them, the star stays in the main sequence star stage for the longest time, and our sun is now in this stage. Scientists use Hertz-Rototo diagram to describe the evolution of stars. The study on the evolution of stars is by far the most accurate scientific research on celestial bodies.

The predecessor of a star is diffuse and thin interstellar matter, which becomes a dense star embryo due to gravitational contraction. In the process of contraction, the center density of embryo increases, the gravitational potential energy is converted into heat energy, the temperature rises, and it gradually glows and heats up. When the central temperature reaches100000 degrees, the thermonuclear reaction of hydrogen fusion to helium becomes the main energy source under high temperature and high pressure, and the embryo becomes a real star. When the energy radiated outward is enough to offset the inward contraction caused by gravity, the contraction stops. Hydrogen in a star burns and becomes helium. With the passage of time, a large amount of helium has accumulated in the stars. With the gradual depletion of hydrogen fuel and the gradual increase of helium, the heat generated by the thermonuclear reaction of hydrogen fusion to helium decreases and the temperature drops. When the energy radiated outward is not enough to resist the inward pressure caused by the massive gravity, the star collapses under the action of gravity, the density of the star increases, the internal pressure increases sharply, and the gravitational potential energy is quickly converted into heat energy. The temperature rises sharply, helium is ignited, helium fusion produces carbon, combustion starts again, and energy radiates violently, which leads to the rapid expansion of the shell, the rapid increase of the star volume and the rapid decrease of the surface temperature, becoming a red giant. After the red giant star, if the star mass is large enough, the above process will be repeated, and carbon will fuse into silicon-based elements. Later, if the mass of the star is larger, silicon will fuse into iron-based elements, and even a supernova explosion will occur. After that, the star will gradually move towards its destination. At the end of the evolution of stars, according to the different masses of stars from small to large, there may be four evolutionary endings: black dwarf, white dwarf, neutron star and black hole.

6. Unsolved mysteries in the universe

The famous popular science writer Asimov said: "Every new discovery in science will open a new mysterious door, and the greatest development often comes from unexpected discoveries, that is, discoveries that overthrow the original views." For the existing cognitive ability and scientific level of human beings, the universe is deep and mysterious. The following are just a few representative phenomena.

● Dark matter

According to some astronomical phenomena that have been discovered and some scientific laws known to mankind, American female astronomer Yingla Robin proposed that there should be a lot of dark matter in the universe, otherwise many phenomena could not be explained. Dark matter may be black holes and dwarfs, but most dark matter should be transparent substances that do not emit light, reflect light or block light. Some scientists say baryon matter, some say photons and some say neutrinos. In short, dark matter in the universe remains an unsolved mystery.

● Quasars

Quasars are a kind of celestial bodies that are particularly bright, small in size, extremely fast in running speed, extremely strong in emission energy and extremely fast in periodic changes of light and shade. Maarten schmidt, an American astronomer, made a deep study of quasars, summed up some phenomena and raised some puzzling questions. But until today, astronomers have not fully reached a * * * understanding of whether quasars are close to us or far away from us, let alone what quasars are.

● Black holes, white holes and hollows

1939 Oppenheimer predicted according to the general theory of relativity that when the mass of a star is large enough (equivalent to more than 3.2 times the mass of our sun), it may collapse due to huge gravity; As its volume becomes smaller, the gravitational field will become very strong, and everything within its gravitational range (scientifically called the horizon) will be sucked in, even the light can't escape, just like an infinite hole. In 1960s, American physicist Wheeler called it a black hole. Some scientists predict that there should be 654.38+0 million black holes in the Milky Way. Because black holes devour all matter and light, at least at this stage, humans can't find a way to directly observe black holes, but scientists have indirectly proved the existence of several black holes.

The white hole is a celestial body with the opposite nature to the black hole. Scientists predict that the white hole is to balance the fluidity of matter in the universe. The matter in the horizon only flows outward, not inward. Wormhole (also called wormhole) is a theoretical hypothesis that must appear after black hole and white hole. It is a possible communication channel between different regions or different universes in the curved space predicted by scientists. Humans still don't know how the universe constructs itself at such a deep level.

7, the big bang universe model

Since Einstein gave the first model of the universe with his general theory of relativity, a new discipline-cosmology was born. Einstein 19 17 put forward a finite and infinite static universe model, in which matter is uniformly distributed and the large-scale characteristics of the universe do not change with time. 1922, the Soviet mathematician Friedman put forward the first dynamic universe model in modern cosmology, suggesting that the universe has two possibilities: expansion and contraction. 1932 Belgian astronomer abbe George Lemaistre proposed that all the substances in the universe should be gathered together first according to the inverse expansion of the universe. 1946, Gamov, a Russian-American scientist, first combined the theory of general relativity cosmology with the theory of chemical element formation, and proposed that the universe started from high-temperature and high-density primitive matter. The initial temperature was as high as several billion degrees, and then it quickly dropped to10 billion degrees. At this time, the universe is full of radiation and elementary particles, and then the temperature begins to drop and the universe begins to expand. When the expansion continued to1100,000 degrees, then Alpha, a student of Gamow, came to the conclusion that the embers of Bigbang15 ~ 20 billion years ago should show the background radiation with a temperature of several K today. When this theory was put forward, it was regarded as a fable by many people and did not attract special attention. 1965, Bob Wilson and arno penzias inadvertently measured the microwave background radiation of 2.7K with the angular antenna of Bell Laboratories. The discovery of cosmic microwave background radiation gives new vitality to the silent big bang universe model.

In the Big Bang universe model, when the universe was born, the density was extremely high, the space was highly curved, and the energy was concentrated as gravitational energy. After the Big Bang, space was full of radiation and isotropy. This raises a question-why can discrete particles appear in a strictly isotropic uniform radiation field? It is predicted that this radiation field may be slightly disturbed, destroying the uniformity of the field and producing particles. 1989, the United States launched the "Cosmic Background Explorer" satellite, 1992, and officially announced that the inhomogeneity of microwave background radiation was detected, which made the Big Bang in the initial state of complete energy: enough to produce particles, and then evolved into the present universe. George Slim processed the data by computer, and got the early universe map, which was vividly called "cosmic egg".

However, there are still many unsolved problems in Big Bang cosmology. For example, what was the universe like before the Big Bang? Did the whole universe originate from this explosion, or is this big explosion just the origin of the universe as we know it? Will the universe, which is still expanding after the explosion, expand forever, or will it stop or turn into reverse contraction one day? ……