In retrospect, the ancients thought that China was the center of the universe and the emperor was the son of heaven. Nobody talks about this anymore. On earth, no one can say that it is the center of the universe. The sun is not the center of the universe. The sun is actually very common in the whole galaxy. There are about 654.38+000 billion various galaxies in the universe, and now the farthest galaxy we know is 654.38+037 billion light years away from the Earth. So what are the so-called galaxies? Refers to a large unit composed of many stars. Some are irregular and can't see the shape; Quite a few are called spiral galaxies, which look like windmills. Our Milky Way is such a spiral galaxy. We can only see that the shape of the galaxy is a line from the side, and we can see the vortex when we look down. This is very different from the universe we originally imagined. 500 years ago, Copernicus proposed that the earth is not in the center of the universe, and that the sun does not revolve around the earth, but the earth revolves around the sun. At that time, the medieval church persecuted him. Copernicus dared not say this until he died. Someone braver than him said it earlier, and the Vatican burned him to death. Now we have made great progress, not only knowing that the earth is not in the center of the universe, but also knowing that the sun is a very ordinary star in the Milky Way. It's neither too big nor too small, neither too old nor too little. It happens to be the sun in its heyday, maintaining the life of the earth.
The time and space scales of the universe are enormous. We know that the sun is 5 billion years old and its life expectancy is 65.438+00 billion years, so it is in middle age. Now the latest estimate is that the death period of the sun will be very long after 5 billion years, because the sun is not a very big star. The big star died soon. The surface temperature of the sun is similar to that of a steel-making furnace (6000 degrees Celsius). Life can only exist in stars like planets of the solar system. People are particularly interested in whether we are the only intelligent life in the universe. Is there a civilization outside the earth? Is the earth the only celestial body with life? The Big Bang produced stars, which in turn formed a planetary system. There are several kinds of planets: one is like Jupiter, which is basically uninhabitable in a big balloon; The other, like the earth, has shells and rocks. From these terrestrial planets, various chemical elements are slowly developed, which are developed to life and finally to human beings. Many astronomers there are searching for extraterrestrial life very carefully. You may see a lot of news about U-FO and aliens. In the movie, aliens have a big head and ugly skin. This is our imaginary alien.
How to find extraterrestrial life? First, it is similar to the chemical composition of life on earth; Second, life depends on liquid water. These two basic points are still questionable. About the source of life, it is still not completely clear. Some people think that life comes from outer space because radio telescopes have observed some molecular clouds far away. At first, only very simple molecules were found in molecular clouds, but now very complex molecules, such as methane molecules, have been observed. Recently, when we explored Mars, we found evidence of the existence of methane on Mars. Because methane is excreted by creatures on earth, people suspect that there are microorganisms on Mars. One idea comes from the molecular cloud that life may come from other planets.
People are born and die, and their life span is about 100 years. Stars also have birth, illness and death. Stars are slowly produced from the Big Bang and dust in nebulae. Stars are in a stable stage for about10 billion years. When we get old after a period of stability, the stars will get sick, the sun will expand, and light and heat will spread and expand, devouring all the planets like the earth. Maybe we will disappear in 5 billion years. Of course, 5 billion years is too long, so it doesn't matter whether it exists or not (laughs). After the outer material of the expanding star ran away, the inner part contracted very little and became a white dwarf. White dwarfs will continue to exist for hundreds of millions of years. This is the life and death of stars. Fortunately, the sun is in its heyday, and it can still provide a lot for the earth.
So why is there life on earth? There are many guarantees on the earth. For example, the earth's atmosphere is like a mosquito net, which hides life from the radiation of high-energy particles in space. In addition, the atmosphere can also prevent direct ultraviolet radiation, so we won't get skin cancer. In addition to the atmosphere, there is also the earth's magnetic field, which hinders the solar wind and many high-energy particles from the universe. High energy particles can penetrate people and cement, which is very harmful. The protection of the earth enables simple creatures to develop into creatures like people.
But now we have a deeper understanding of life. After deep-sea exploration, it is found that there are more kinds of creatures in the ocean than on the mainland. For example, the lotus seeds 5,000 years ago can be planted, germinated and grown into lotus roots after being found in ancient tombs, which is very rare. But there are many creatures in the cracks in the deep sea, where there is no sunshine and no oxygen. These creatures live on other ingredients, such as methane. After they decompose methane, they get oxygen to survive. But water is really indispensable. So far, no life that can survive without water has been found. Are there any creatures in the ocean that can withstand the high temperature above 100 degrees? There are bacteria and organisms more complicated than bacteria on the high temperature water surface near the volcanic fountain in Yellowstone National Park 100 degrees. So it's hard to say whether life comes from the sky or the earth. Maybe everyone will say that it should come from the sky, and then find a suitable place on the ground, where there is an ocean, and then plant it. I want to leave it to you to look at other people's research results in the future, or to participate in the research in person and see where life originated.
We should not only look for life, but also look for intelligent life like human beings. To find intelligent creatures, you must at least have the ability of long-distance communication.
We should not only look for life, but also look for intelligent life like human beings. What are our hopes? As I said before, life can only exist in stars such as planets in the solar system. Calculate probability. Now we know that the Milky Way has120 billion stars, or 654.38+04 billion stars to be exact. There are about 654.38+000 billion stars with medium mass that can be compared with the sun. How many of these stars can have planets? We don't know. How many planets are similar to the earth? Planets that are too big, such as Jupiter, are all gases and cannot have life; Too small, there is no life without atmosphere. What does it take to form life? There must be water and appropriate chemical elements. How many can become intelligent creatures after the end of life? If you want to find intelligent creatures, you must at least have the ability of long-distance communication. Why must it be a long distance? Because the nearest star is 4 light years away, if we can communicate, we will send him a signal and he will send it back. After 300 years, it will be stored in the historical archives to make an echo. One more thing, just now, it was said that stars live and die, and the signal came out that the whole galaxy and the whole star died, so it might not be found. So you must have communication skills, and the other party can't die. In this way, multiplying all the probabilities is the ratio of how many of the 654.38+000 billion stars are likely to find intelligent life.
So has anyone done this research? There is a research unit called SETI, which specializes in searching for extraterrestrial intelligent life. It's really a serious search, but nothing has been found since 1960. Its search idea is to use the arecibo radio telescope with a diameter of 300 meters on the ground. Two years ago, I searched in Australia with a radio telescope with a diameter of 64 meters for half a year. How can we find that alien signal? First of all, the artificial signal should have a narrow frequency band, while the natural signal has a lot of noise and a wide frequency band, so just look for the signal of 1 Hz, and you can find the signal of 1 Hz with a large spectrometer and receivers with almost thousands of channels. How do you know it's from outer space? The most important way is to find an auxiliary radio telescope hundreds or thousands of kilometers away from the main telescope. Suppose there is a sign, ask him to look at it quickly. If everyone sees this signal in the same direction and channel, they will regard it as a possible detection signal, and then eliminate all kinds of human interference, including radar, satellites and space military tests. There are millions of signals that can be considered in the past 40 years, but none of them have been found after being eliminated. Unfortunately, we must wait for your efforts. Ten years ago, I had a meeting abroad. There were a group of people who were very enthusiastic about SETI at the meeting. At that time, they thought it was likely to be found, so they launched a declaration at the meeting. The declaration says that if anyone receives a signal of intelligent life from space, he has no right to answer it on behalf of the earth, and he must go through a Committee to discuss how to answer it. We think it is too early to sign the declaration at the meeting. Is the Committee authoritative enough? Should we sign it? In the end, everyone rejected it and did not participate in the signing. However, SETI has research institutions all over the world, and we meet every few years to continue our research. We are one of the enthusiastic people. What we do is to eliminate UFOs, anything that cannot be confirmed, and formally and seriously look for extraterrestrial civilization.
Some people ask, why can't we only receive signals from alien life? If we send it there and bring back a very powerful radio signal, this energy is too great for us now. So at present, it is easier to listen with your ears than to send signals. I hope you can send a signal with enough power to wait for an answer in a very cheap way after work. On the other hand, if aliens can really come by flying saucer, we can see that their civilization development is much higher than that of the earth, otherwise it is impossible to see us from many light-years away, and we really need to admit that their civilization is much higher than that of current human beings. At that time, aliens came to see us just as we see gorillas today. But people's mobility is infinite, and I believe you will have the opportunity to find such reliable information in this generation or the next.
How many small celestial bodies are there near the earth? What if it's really close? How to break it? How to change its orbit to avoid human suffering? This is a very serious scientific research.
We are talking about space exploration now. 1963 Americans landed on the moon. The first astronaut said a famous saying: landing on the moon is a small step for individuals and a big step for mankind. The manned lunar rover went very fast, but now the unmanned lunar rover goes very slowly. Because it can't distinguish the surrounding obstacles, people on the ground must see it before giving instructions, otherwise the rover will "sacrifice" if it falls into the ditch and can't get out. Humans are still looking for extraterrestrial life on Jupiter. Jupiter's volume is more than 1300 times that of the earth, and its mass is more than 300 times that of the earth. We found many moons of Jupiter and the shadow of water on Europa, and it is likely that there is life. The American spacecraft Galileo explored Jupiter. It circled Jupiter 34 times and flew more than 4.6 billion kilometers. Later Galileo exploded, because if we left it around Jupiter, it would crash Jupiter's natural satellite, so we might as well throw it into the atmosphere and burn it. Another important achievement of Jupiter exploration is that comets collide with each other. That's really spectacular, but it also gives us a warning that since the comet will hit Jupiter, it may also hit the earth. The surface of the moon is covered with craters. At that time, the United States Congress passed a resolution requiring astronomers to immediately organize forces to study whether any small celestial bodies that are very close to the Earth may hit the Earth. How many small celestial bodies are there near the earth? What if it's really close? How to break it? How to change its orbit to avoid human suffering? This is a very serious scientific research, including the research in which China participated.
At first, people thought there were canals on Mars, and the photos looked like a person's face. 1964, the spacecraft to explore found that there was no canal at all. 1976 landed on Mars and no life was found. Now it's changed. I thought there might be microorganisms. Some people think that these microorganisms may be brought by the original spacecraft, but this possibility is not reliable, because there will not be so many. Later, I found traces of running water. Recently, two rovers have been working on Mars and will bring back samples of Mars for research next year. China's rocket capability is enough to go to Mars, but it has never tried to run so far and control so far. Some colleagues in the Academy of Sciences said that preparations for Mars exploration should be made immediately after the lunar exploration. We still have many questions about Mars. Why is there so much dust? Why is the magnetic field gone? Where did the moisture go? There's always news. The latest news is that there is methane on Mars, and there are probably microorganisms.
I encourage you to explore alien life. At the international astronomical conference held in Australia last year, it was announced that there were 1 17 stars with planets around them. Now it is estimated that there are about 150, and the number is still increasing. There are many ways to detect extraterrestrial civilization. One is to receive the signal, and the other is to take out the signal. 1977 Traveler 1 2 brought a gold record called Voice of the Earth. There are 1 16 pictures on it; 55 languages, including Chinese, all say "good morning"; 35 natural sounds; 27 pieces of music, including China ancient music. 1972, 1973 "pioneer" 10,1/exit belt sign. There are 14 pulsars on the signboard. I hope that aliens will know the center of the Milky Way and find the sun when they see the pulsars. Our nine planets are also arranged below, as well as the appearance of human beings, spaceships and so on. If aliens are smart enough, we will know that we are earthlings when we get this board.
Only when people can go to heaven can a space station be built. When there is no plane, whoever has a plane will have air superiority. Once there is a space station, many defense and even distribution satellites can be realized in space. Don't underestimate manned space flight.
What do we need to do? We should explore the moon first, then Mars, then Jupiter, and then see how far we can go. Someone asked us why we spent so much money to build the Shenzhou 5 ... After the launch of Shenzhou 5, it had a great impact on the world. Our colleagues engaged in radio observation sent many congratulatory letters, and specially reported our Shanghai team in the magazine. It is not unusual for some people to fly to the sky, because Gagarin has been in the sky for 45 years. What's so rare? Actually, it is not, because people's requirements for the environment and safety are much higher than those of satellites. The first time we sent a manned spacecraft into the sky was because we wanted to ensure success, so the action was relatively simple. But there are still many things behind, such as Shenzhou VI and Shenzhou VII, which will increase from one astronaut to three, and the most important thing is to walk in space, all for our future space laboratory and space station. It would be great if we can leap to the level of the space station soon. Only when people can go to heaven can they build a space station, and the military significance can be imagined. When there is no plane, whoever has a plane will have air superiority. Once there is a space station, many defenses and even sending satellites can be realized in space. Therefore, we should not underestimate manned space flight. There are many developments that need us to leap forward.
We want to launch a lunar exploration satellite, first of all, we must fly around the moon. Our first lunar exploration was to make a three-dimensional topographic map of the whole moon. The United States has not yet made a full moon, about 75 degrees. The second is to detect minerals. Five useful minerals have been detected in the United States, and we want to detect 14. The third is to explore energy. At present, there is a shortage of oil supply. It is estimated that in less than 50 years, all oil stocks will be used up, and natural gas will not be used for long. Although there are many coal reserves, they are all in inaccessible and difficult-to-mine places. Japan bought a lot of good coal, which is not needed, and the coastline will be badly needed one day. Judging from the nuclear power plants, there are two or three in China. What we are doing now is to obtain atomic energy from nuclear fission, and the required heavy elements are not much in stock on the earth. China is also a depleted uranium country, and it is estimated that it will be used up in about 50 years. Atomic energy and nuclear fusion, the energy of the sun comes from nuclear fusion, which turns hydrogen into helium, and excess mass into energy to emit light and heat. But people can't control nuclear fusion well. They can make hydrogen bombs, but they can't make nuclear power plants. Now they are making great efforts to study controlled nuclear fusion. Helium III, the main raw material, is rare on the earth. It comes from satellites and the solar wind. There is no atmosphere on the moon, and helium 3 can easily reach the surface of the moon, forming a high soil content. If we can "scrape the ground on the moon" and bring the helium in the soil back to the earth, it can be used on the earth for a long time. This lunar exploration is to detect how thick the lunar soil is and estimate the helium -3 content.
So is Mars. There is almost no atmosphere and water on Mars now, and life, if any, is very elementary. Some scientists seriously consider this problem: the greenhouse effect has caused great harm to the earth, but if the greenhouse effect is also based on the very cold surface of Mars and a thicker atmosphere is established, its temperature will rise and the ice will melt. Suppose we take the seed there again, it will become an oasis where people can live. Of course, it takes seven months to go to Mars once, which may be too long. But if the earth is full and the resources are exhausted, we still have to emigrate.
Whether it's China or exploring the moon and Mars, this is the performance of comprehensive national strength. Considering energy, territorial development and self-defense, space exploration is necessary. Although it looks expensive, it is not too expensive, and it is not unworthy to use the power of the whole country to do these jobs. The problem is that if there is no preparation, even if the central government gives 654.38+000 billion, it will not fly to Mars. You can't buy this. You must accumulate a lot of skills and cultivate a lot of scientific strength in order to move forward step by step. So we are very happy that the lunar exploration plan has been approved by the central authorities. It is also a matter of time why the Central Committee will approve it. Exploring the moon, the United States did it, the Soviet Union did it, Japan's plan started before us, and India is also doing it, claiming that it will go to the moon in 2008, so we are in a hurry. We should do what we want to do safely in advance.
I introduced you to the vastness of the universe. I hope you can find aliens one day, and also hope to use the territory and resources outside the earth to benefit mankind. The bread here contains a lot of very high technology, so we walk fast for fear that we can't catch up. Take the lunar rover as an example. At present, many units in China are developing it, but it gives everyone the feeling that it is stupid and heavy, and it is far from a good lunar rover without many monitoring equipment. Fortunately, we still have time to keep trying. In a few years, you will all graduate. I hope someone can participate in the second and third phases of lunar exploration and play a role. We agree here that some of you want to be astronauts, some want to be the host of receiving equipment, and some want to continue to contribute to future research. I think this is our common wish.