英语听力英语高级听力材料Supermassive Black Holes.docx

1、英语听力英语高级听力材料Supermassive Black HolesIn March 2000, two astronomers made an extraordinary discovery, one that is set to overturn our understanding of how the universe formed.Were never going to see a time like this in astronomy again.Really, the air is filled with new discoveries and new ideas.What t

2、hey discovered was a very simple relationship, a relationship between the galaxy we live in and the most destructive force in the universe, a supermassive black hole. It set the world of cosmology alight.People were not that excited about supermassive black holes. The general astronomer did not care

3、 that much about supermassive black holes. Now they have to and, now theyd better.The ultimate aim of cosmology is to understand how the universe was formed. One of the most important questions is how galaxies were created, because without them we wouldnt exist.Galaxies contain almost all of the sta

4、rs we see in the universe and, maybe the places where all stars in the universe will be created. And stars are what produce oxygen, carbon, planets, everything you need for life. And without life you dont get astronomers.We see our galaxy, the Milky Way, as a band of stars in the sky. In fact, it is

5、 a giant rotating disc, 200,000 light years wide. It contains over 200 billion stars like our own sun, circling slowly around the center.But we are just one in 125 billion galaxies of different shapes and sizes spinning through space. Yet scientists havent been able to explain how a single one of th

6、ese galaxies was created.Galaxy formation is a very complicated process, we think, it involves gravity and it involves large balls of gas colliding, it involves the dynamics of stars and it involves the chemistry of the gas coming together.All we know is that when the universe was young, there were

7、no stars or planets, just great swirling clouds of hydrogen gas. The mystery is how each of these clouds turned into the complex galaxies of stars we see today.We just dont know how they do it, how galaxies formed out of the, the ionized hot gas that(s) filled the universe is still physics that we d

8、o not really understand yet.Exactly how galaxies were created has troubled the worlds leading astronomers and physicists for decades. But in March 2000, scientists found evidence for an extraordinary answer.The Nuker team is a group of world respected astronomers, but they are not galaxy experts. Th

9、ey are experts in the most violent and destructive forces known to science-supermassive black holes. Until recently, supermassive black holes were mere theory. These are giant black holes of apocalyptic proportion.Supermassive black holes are a million to a billion times the mass of, of a, of a typi

10、cal black hole.They could fill a whole solar system.A supermassive black hole is quite simply gravity gone mad. An object of such concentrated matter its gravitational pull is insatiable. Nothing can escape it, not even light itself. Anything that gets close- gas, stars and entire solar systems are

11、sucked into oblivion. It even destroys the very fabric of the universe. If you think of the universe as a space-time web, the gravity of ordinary stars and planets creates a dent in this web. But the immense gravity of a supermassive black hole is so destructive that it distorts spacetime to breakin

12、g point.At the heart of a supermassive black hole is one of the most mysterious things in physics-the singularity(奇点), a point where space, time and all known laws of physics fall apart.What happens at the center of the singularity is a complete mystery. And solving it is going to require new physic

13、s that we just dont have right now. Some people think you can fall through the singularity and pop out in another part of the universe. The theories for the singularity are, some of them are very, very radical. We just dont know.Supermassive black holes are so bizarre that until recently many scient

14、ists doubted they existed at all. They were an extreme idea dreamt up to explain a very rare and distant type of galaxy: active galaxies. These are amongst the brightest objects in the universe. These galaxies have a brilliant burning core with vast jets of energy spurting out of the center.oblivion

15、: destruction, extinctionspace-time: the four-dimensional continuum in which all objects are located and all events occur, viewed as a single and continuous framework for existence. Space-time consists of length, width, depth, and time.singularity: Astrophysics. A point in space-time at which gravit

16、ational forces cause matter to have infinite density and infinitesimal volume, and space and time to become infinitely distortedan active galaxy is a galaxy where a significant fraction of the energy output is not emitted by the normal components of a galaxy: stars, dust and interstellar gas. This e

17、nergy, depending on the active galaxy type, can be emitted across most of the electromagnetic spectrum, as infrared, radio waves, Ultra Violet, X-ray and gamma rays.This ferocious heart of brilliant hot gas is called a quasar. Scientists thought this whirling mass might be caused by a giant black ho

18、le sucking up gas and stars, literally feeding on the center of a galaxy.The idea is that the quasars that we see that look so bright are not the black hole, the supermassive black hole. They are the gas thats just about to fall into the supermassive black hole, thats going around it, shining very b

19、rightly just before it disappears down into the black hole.A giant black hole would have a gravitational pull so overwhelming, it would hurl gas and stars around it at almost the speed of light. The violent clashing would heat the gas up to over a million degrees.The gas rubs against itself essentia

20、lly and gets extremely hot, and extremely hot gas shines very brightly.In reality, although a quasar burns brightly, it is actually impossible to see if theres a black hole in the middle. Paradoxically, the black hole is made invisible by the fact that it swallows light. So for years, no one could b

21、e certain if supermassive black holes really did exist at the heart of these strange active galaxies. The Nukers have spent the last two decades hunting for these elusive monsters. The first problem they faced was to prove that supermassive black holes existed at all. What they were to discover woul

22、d be stranger than most people could have imagined. One of the first of the Nukers to try to find one was Alan Dressler. In 1983 he came to the Palomar Telescope in California convinced that hed found a way to prove that supermassive black holes exist.You cant see a black hole directly. Thats what m

23、akes it a black hole. So what you are looking for is evidence of its gravity. You are ever looking at how it pulls on the stars that are coming nearby.Dressler knew that although a black hole is invisible, its immense gravity would hurl stars around it at over 500,000 kilometers an hour.quasar: 类星体

24、Astronomy a massive and extremely remote celestial object which emits large amounts of energy and typically shows a starlike imageBy measuring how fast these stars were moving, he could prove if there really was a black hole at the center of an active galaxy.I picked a galaxy nearby which is called

25、NGC 1068, an active galaxy, which meant that it probably had a supermassive black hole in it, at least, thats what we wanted to prove.To be certain that the stars were moving unnaturally fast in NGC 1068, Dresslar wanted to compare them with stars in a normal galaxy without a black hole. Stars circl

26、ing around a weak center of gravity would move at half the speed. So for this comparison, he chose the very ordinary galaxy next door to us, Andromeda(仙女座), with a quiet, inactive center like our own.To measure the speed of the stars in these two very different galaxies, Dresslar used an instrument

27、called a spectroscope. This looks at the changing pattern of light coming from stars as they rotate around the galaxy core. The spectroscope shows the center of the galaxy as a white band and the movement of stars around the core is traced by a dark, vertical line. If the stars of the galaxys center

28、 are circling slowly, then the dark band would show hardly any change, but if they are traveling at great speed, whizzing towards and away from us either side of a supermassive black hole, then the dark band should show a sudden shift across the center of the galaxy.I would expect to see some rather

29、 rapid change in this dark line so that thered be a very big change in the speed from one side of the galaxy to the other, very suddenly, right over the center and that would show that the stars were moving very rapidly in the center of the galaxy because of the influence of the great mass in the ce

30、nter, the supermassive black hole.Over the next a few nights, Dresslar measured the speed of the stars in NGC 1068 and in Andromeda.spectroscope: an apparatus for producing and recording spectra for examinationwhiz: move quickly through the air with a whistling or whooshing soundWhen the results cam

31、e down from the telescope he saw something that was completely unexpected. The picture from the active galaxy where he hoped to find a black hole was unreadable. NGC 1068 was just too far away for the telescope to get a clear picture. The surprise came from Andromeda, the quiet, normal galaxy right

32、next to us.I was astonished when I found what I was looking for, but not where I was looking for it. This jog in this dark band shows that on one side the stars are moving very rapidly away from us at 150 kilometers a second which is 500,000 kilometers an hour.Dressler thought there could only be one thing that would cause the stars to move this fast: a supermassive black hole and he wasnt alone. Fellow Nuker John Kormendy had found exactly the same thing.The moment I could see that wiggle, so I knew essentially instantly that there was a very good chance this would be a supermassive