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背景参考资料(Background knowledge) The planets in the solar system1. The Sun is a star - it is not a planet. It is the only star we see during the daytime. The Sun measures more than a million kilometers across.Its center is about 15 million degrees Celsius. It is about 75% hydrogen and 25% helium.The Suns energy is produced by nuclear fusion reactions. It generates 386 billion megawatts of energy!2. Mercury is a small, rocky planet.Scientists think that there may be volcanic activity on Mercury, but they arent sure. The temperature on Mercury ranges from 90 K to 700 K. It was once believed that there was no water on Mercury, but this turned out to be false. Recent radar information shows evidence of ice at Mercurys north pole! The ice hasnt melted because it is protected from the Suns heat by shadows of some craters. 3. Venus is a small, rocky planet blanketed in a thick layer of yellowish clouds. These clouds are not made of water. Instead, they are formed from a poison called sulfuric acid. Its surface is about 400 degrees Celsius, so is too hot for rain to form.4. Earth is a small, rocky planet which supports a variety of life! Temperatures at the Earths center may be as high as 7500 K - Thats hotter than the surface of the Sun! The Earth is the densest major body in the solar system. The Earth is 4.5 to 4.6 billion years old, but the oldest known rocks are less than 4 billion years old. The Earth is orbited by one moon.5. Mars is a small, rocky planet which is cold and lifeless.Mars has permanent ice caps at both poles made up mostly of solid carbon dioxide. We know this as dry ice. Very strong winds and vast dust storms sometimes blow through the entire planet for months! Mars has two tiny moons which orbit very close to the surface.6. Jupiter is a giant gas planet which is made up of about 90% hydrogen and 10% helium. Jupiter is so big that you could cram 1,000 Earths inside of it! It is thought that Jupiters Great Red Spot is a storm of swirling gas that has lasted for hundreds of years. Jupiter has 16 known moons! 7. Saturn is a giant gas planet which is made up of about 75% hydrogen and 25% helium. Its most famous for its thousands of beautiful rings. Its rings are made up mostly of water ice, but they may also include rocky particles with icy coatings. Saturn is made up of materials which are lighter than water. If placed in a big pond, Saturn would float much like an ice cube does in a glass of water. Saturn has 18 known moons - more than any other planet! 8. Uranus is a giant gas planet which is made up of mostly rock and various ices. Uranus has 15 known moons. Voyager 2 discovered 10 small moons in addition to the 5 large ones already known. 9. Neptune is a giant gas planet which is most likely made up of various ices" and rock. Neptune has been visited by only one spacecraft, Voyager 2 on Aug 25 1989. Almost everything we know about Neptune comes from this one visit. It has 8 known moons.10. Most of the Moons surface is covered with a mixture of fine dust and rocky debris .The Moon has no atmosphere. But evidence suggests that there may be water ice in some deep craters near the Moons south pole. Most rocks on the surface of the Moon seem to be between 4.6 and 3 billion years old. The gravitational forces between the Earth and the Moon cause some interesting effects. The most obvious is our ocean tides. About black holes(1)After almost 30 years of arguing that a black hole swallows up everything that falls into it, British astrophysicist (天体物理学家) Stephen Hawking moved backward last week.The world-famous writer of Brief History of Time said he and other scientists had got it wrong. Ive been thinking about this problem for the last 30 years, and I think I now have the answer to it, said Hawking. A black hole only appears to form but later opens up and set free information about what fell inside. So we can be sure of the past and can predict the future.The findings could help solve the black hole information paradox（似是而非的观点）, an important puzzle in modern physics.A black hole is an area in space where matter is under such pressure that even light can not escape from its gravitational pull(引力). But, exactly what happens there has long puzzled scientists.Black holes occur when a powerful star burns up its nuclear fuel and gravity forces it to break down in on itself. The great weight of the stars outer layers moves in towards its center. The force of gravity keeps nearly all light from escaping and nothing inside can be seen from the outside.The star actually disappears from the universe into a point of infinite density（高密度）. That is a place where the laws of general relativity that govern space and time break down.Hawking has devoted most of his life to studying these questions.At the beginning, cosmologists believed the holes were like a universal vacuum (真空) cleaner, sucking up everything in their path.Hawking revolutionized the study of black holes when he proved, in 1976 that, under the strange rules of quantum physics（量子物理）, when black holes form they send out energy and lose mass in the process.In thinking up this so-called Hawking radiation, the Cambridge mathematician also created one of the biggest puzzles in physics.These particles (粒子), he said, contained no information about what has been occurring inside the black hole, or how it formed. Under his theory, once the black hole disappears, all the information within it is lost.Black holes (2)(1) What is a black hole? Well, its difficult to answer this question, since the terms we would normally use to describe a scientific phenomenon are inadequate here. Astronomers and scientists think that a black hole is a region of space (not a thing ) into which matter has fallen and from which nothing can escape- not even light. So we cant see a black hole. A black hole experts a strong gravitational pull and yet it has no matter. It is only space - or so we think . how can this happen? (2) The theory is that some stars explode when their density increases to a particular point; they collapse and sometimes a supernova occurs. Form earth , a supernova looks like a very bright light in the sky which shines even in the daytime. Supernovae were reported by astronomers in the seventeenth and eighteenth centuries. Some people think that the Star of Bethlehem could have been a supernova. The collapse of a star may produce a White Dwarf or a neutron star- a star , whose matter is so dense that it continually shrinks by the force of its own gravity. But if the star is very large (much bigger than our sun) this process of shrinking may be so intense that a black hole results. Imagine the earth reduced to the size of a marble, but still having the same mass and a stronger gravitational pull, and you have some idea of the force of a black hole. Any matter near the black hole is sucked in. It is impossible to say what happens inside a black hole. Scientists have called the boundary area around the hole the event horizon. We know nothing about events which happen once objects pass this boundary. But in theory, matter must behave very differently inside the hole. (3) For example , if a man fell into a black hole, he would think that he reached the center of it very quickly. However an observer at the event horizon would think that the man never reached the center at all. Our space and time laws dont seem to apply to objects in the area of a black hole. Einsteins relativity theory is the only one which can explain such phenomena , so that there is no absolute time and space depend on the position of the observer. They are relative. We do not yet fully understand the implications of the relativity theory; but it is interesting that Einsteins theory provided a basis for the idea of black holes before astronomers started to find some evidence for their existence. It is only recently that astronomers have begun specific research into black holes. In August 1977, a satellite was launched to gather data about the 10 million black holes which are thought t be in the Milky way. And astronomers are planning a new observatory to study the individual exploding stars believed to be black holes. (4) The most convincing evidence of black holes comes from research into binary star systems. Binary stars, as their name suggests, are twin stars whose position in space affects each other. In some binary systems, astronomers have shown that there is an invisible companion star, a partner to the one which we can see in the sky. Matter from the one we can see is being pulled towards the companion star. Could this invisible star, which exerts such a great force , be a black hole? Astronomers have evidence of a few other stars too, which might have black holes as companions. (5) The story of black holes is just beginning . Speculations about them are endless. There might be a massive black hole at the center on our galaxy swallowing up stars at a very rapid rate. Mankind may one day meet this fate. On the other hand, scientists have suggested that very advanced technology could one day make use of the energy of black holes for mankind. These speculations sound like science fiction. But the theory of black holes in space is accepted by many serious scientists and astronomers .they show us a world which operates in a totally different way from our own and they question our most basic experience of space and time. Read the passage carefully and choose the best answer for the following questions 1) Black holes are related to _ A. geography B. astronomy C. physics D. economic 2) A black hole is _ A. a dark star B. a large heavenly body C. a region of space D. a great mass of matter 3) what causes some stars to explode, theoretically speaking ? A. their density B. their gravity. C. their movement D. their light 4) Scientists call the area around the black hole _. A. a White Dwarf B. a supernova C. the event horizon D. the star of Bethlehem 5) according to Einsteins relativity theory, there is no absolute time and space. Is it true or false? A. true B. false 6) which of the following statements is not true? The story of black holes in space_ A. is accepted by many serious scientists and astronomers B. has to some extent been proved by research into binary star system C. is questioning our basic idea of space and time D. Sounds like science fiction 7) according to the passage , our earth may be swallowing by the black hole one day, is it true or false ? A. true B. false 8) according to the passage , the human being one day may make use of the energy of black hole by advanced technology. Is it true or false?单位：湖北省荆门姓名：李国E_mail：liguo619
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