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更多“When would they start the trip？”相关的问题
第1题
Black Holes Trigger Stars to Self-Destruct
Scientists have long understood that super massive black holes weighing millions or billions of suns can tear apart stars that come too close. The black hole's gravity pulls harder on the nearest part of the star, an imbalance that pulls 'the star apart over a period of minutes or hours, once it gets close enough.
Scientists say this uneven pulling is not the only hazard facing the star. The strain of these unbalanced forces can also trigger a nuclear explosion powerful enough to destroy the star from within. Matthieu Brassart and Jean-Pierre Luminet of the Observatoire de Paris in Meudon, Francel, carried out computer simulations of the final moments of such an unfortunate star's life, as it veered towards a super massive black hole.
When the star gets close enough, the uneven forces flatten it into a pancake shape. Some previous studies had suggested this flattening would increase the density and temperature inside the star enough to trigger intense nuclear reactions that would tear it apart. But other studies had suggested that the picture would be complicated by shock waves generated during the flattening process and that no nuclear explosion should occur.
The new simulations investigated the effects of shock waves in detail, and found that even when their effects are included, the conditions favor a nuclear explosion. "There will be an explosion of the star—it will be completely destroyed," Brassart says. Although the explosion obliterates the star, it saves some of the star's matter from being devoured by the black hole. The explosion is powerful enough to hurl much of the star's matter out of the black hole's reach, he says.
The devouring of stars by black holes may already have been observed, although at a much later stage. It is thought that several months after the event that rips the star apart, its matter starts swirling into the hole itself. It heats up as it does so, releasing ultraviolet light and X-rays.
If stars disrupted near black holes really do explode, then they could in principle allow these events to be detected at a much earlier stage, says Jules Halpern of Columbia University in New York, US2. "It may make it possible to see the disruption of that star immediately if it gets hot enough," he says.
Brassart agrees. "Perhaps it can be observed in the X-rays and gamma rays, but it's something that needs to be more studied," he says. Supernova researcher Chris Fryer of the Los Alamos National Laboratory in Los Alamos, New Mexico, US3, says the deaths of these stars are difficult to simulate, and he is not sure whether the researchers have proven their case that they explode in the process.
Something destructive could happen to a star that gets too close to a black hole. Which of the following destructive statements is NOT mentioned in the passage？
A．The black hole could tear apart the star.
B．The black bole could trigger a nuclear explosion in the star.
C．The black hole could dwindle its size considerably.
D．The black hole could devour the star.
第2题
Black Holes Trigger Stars' Self-destruction
Scientists have long understood that super massive (大块的) black holes weighing. Millions or billions of suns can tear apart stars that come too close. The black hole's gravity (地心引力) pulls harder on the neatest part of the star, an imbalance that pulls the star apart over a period of minutes or hours, once it gets close enough.
Scientists say this uneven pulling is not the only hazard (冒险) facing the star. The strain of these unbalanced forces can also trigger (触发) a nuclear explosion powerful enough to destroy the star from within. Matthieu Brassart and Jean-Pierre Luminet of the Observatoire of the Paris in Meudon, France, carried out computer simulations of the final moments of such an unfortunate star's life, as it veered towards a supermassive black hole.
When the star gets Close enough, the uneven forces flatten it into a pancake shape. Some previous studies had suggested this flattening would increase the density and temperature inside the star enough to trigger intense nuclear reactions that would tear it apart (扯开). But other studies had suggested that the picture would he complicated by shock waves generated during the flattening process and that not nuclear explosion should occur.
The new simulations investigated the effects of shock waves in detail, and fund that even when their effects are included; the conditions favor a nuclear explosion. "There will be an explosion of the star. It will be completely destroyed," Brassart says. Although the explosion obliterates the star, it saves some of the start's matter from being devoured by the black hole. The explosion is powerful enough to hurt much of the star's matter out of the black hole's reach, he says.
The devouring of stars by black holes may already have been observed, although at a much later stage. It is thought that several months after the event that rips the star apart, its matter starts swirling into the hole itself. It heats up as it does so, releasing ultraviolet light and X-rays.
If stars disrupted (使分裂) near black holes really do explode, then they could in principle allow these events to be detected at a much earlier stage, says Jules Halpern of Columbia University in New York, US. "It may make it possible to see the disruption of that star immediately if it gets hot enough. "
Brassart aggress. "Perhaps it can be observed in the X-rays and gamma rays, but it's something that needs to be more studied , "he says. Supernova researcher Chris Fryer of the Los Alamos National Laboratory in Los Almos, New Mexico, US, says the deaths of these stars are difficult to simulate, and he is not sure whether the researchers have proven their case they exploded in the process.
Something destructive could happen to a star that gets too close to a black hole. Which of the following statements is NOT mentioned in the passage？
A．The black hole could tear apart the star.
B．The black hole could trigger a nuclear explosion in the star.
C．The black hole could dwindle its size considerably.
D．The black hole could devour the star.
第3题
听力原文： In ancient times, many people believed tile earth was a flat disc. Well over 2,000 years ago, rite ancient Greek philosophers were able to put forward two good arguments proving that it was not. Direct observations of heavenly bodies was the basis of both these arguments. First, the Greeks knew that during eclipses of the moon, file earth was between the sun and the moon, and they saw that during these eclipses, the earth's shadow on the moon was always round, they realized that this could be true only if the earth was spherical. If tile earth were a flat disc, then its shadow during eclipses would not be a perfect circle, it would be stretched out into a long ellipse. Tile second argument was based on what the Greeks saw during their travels. They noticed that the North Star, or Polaris, appeared lower in the sky when they traveled south, in more northern regions, the North Star appeared to them to be much higher in file sky. By the way, it was also from this difference in the apparent position of the North Star that the Greeks first calculated the approximate distance around the circumference of the earth, a figure recorded in ancient documents says 400,000 stadia, that's the plural of the word stadium. Today, it's not known exactly what length one stadium represents, but let's say, it was about 200 meters, the length of many athletic stadiums. This would hake the Greek' s estimate about twice the figure accepted today, a very good estimate for those writing so long before even the first telescope was invented.
(33)
A．How ancient philosophers measured the distance between heavenly bodies.
B．How ancient philosophers explained the cause of an eclipse of the Moon.
C．Why ancient philosophers thought the Earth was a sphere.
D．Why ancient philosophers thought the Earth moved around the Sun.
第4题
请根据短文内容，回答题。
Black Holes
Most scientists agree that black holes exist but are nearly impossible to locate. A black hole in the universe is not a solid object, like a planet, but it is shaped like a sphere (球体). Astronomers(天文学家) think that at the center of a black hole there is a single point in space with infinite (无限的 ) density (稠密 ) . This single point is called a singularity (奇点). If the singularity theory is correct, it means that when a massive star collapses, all the material in it disappears into the singularity. The center of a black hole would not really be a hole at all, but an infinitely dense point.＜br＞
Anything that crosses the black hole is pulled in by its great gravity.＜br＞
Although black holes do exist, they are difficult to observe. These are the reasons.＜br＞
No light or anything else comes out of black holes. As a result, they are invisible to a telescope.＜br＞
In astronomical terms, black holes are truly. For example, a black hole formed by the collapse of a giant star would have an event horizon (视界) only 18 miles across.＜br＞
The nearest black holes would be dozens of light years away from Earth. One light year is about 6 trillion (万亿) miles. Even the most powerful telescopes could not pick out an object so small at such a great distance.＜br＞
In 1994 the Hubble Space Telescope provided evidence that black holes exist. There are still answers to be found, however, so black holes remain one of the mysteries of the universe.＜
Black holes are part of space. 查看材料
A.Right
B.Wrong
C.Not mentioned
第5题
根据下面材料，回答题。
Black Holes
Most scientists agree that black holes exist but are nearly impossible to locate. A black hole in the universe is not a solid object, like a planet, but it is shaped like a sphere (球体). Astronomers(天文学家) think that at the center of a black hole there is a single point in space with infinite (无限的) density (稠密). This single point is called a singularity (奇点). If the singularity theory is correct, it means that when a massive star collapses, all the material in it disappears into the singularity. The center of a black hole would not really be a hole at all, but an infinitely dense point.
Anything that crosses the black hole is pulled in by its great gravity.
Although black holes do exist, they are difficult to observe. These are the reasons.
？ No light or anything else comes out of black holes. As a result, they are invisible to a telescope.
？ In astronomical terms, black holes are truly. For example, a black hole formed by the collapse of a giant star would have an event horizon (视界) only 18 miles across.
？ The nearest black holes would be dozens of light years away from Earth. One light year is about 6 trillion (万亿) miles. Even the most powerful telescopes could not pick out an object so small at such a great distance.
In 1994 the Hubble Space Telescope provided evidence that black holes exist. There are still answers to be found, however, so black holes remain one of the mysteries of the universe.
Black holes are part of space. 查看材料
A.Right
B.Wrong
C.Not mentioned
第6题
Black Holes
Most scientists agree that black holes exist but are nearly impossible to locate. A black hole in the universe is not a solid object, like a planet, but it is shaped like a sphere (球体). Astronomers (天文学家)think that at the center of a black hole there is a single point in space with infinite (无限的)density (稠密). This single point is called a singularity (奇点). If the singularity theory is correct, it means that when a massive star collapses, all the material in it disappears into the singularity. The center of a black hole would not really be a hole at all, but an infinitely dense point. Anything that crosses the black hole is pulled in by its great gravity.
Although black holes do exist, they are difficult to observe. These are the reasons.
-- No light or anything else comes out of black holes. As a result, they are invisible to a telescope.
-- In astronomical terms, black holes are truly. For example, a black hole formed by the collapse of a giant star would have an event horizon(视界)only 18 miles across.
-- The nearest black holes would be dozens of light years away from Earth. One light year is about 6 trillion(万亿)miles. Even the most powerful telescopes could not pick out an object so small at such a great distance.
In 1994 the Hubble Space Telescope provided evidence that black holes exist. There are still answers to be found, however, so black holes remain one of the mysteries of the universe.
Black holes are part of space.
A．Right
B．Wrong
C．Not mentioned
第7题
Suppose a man wanted to reach a distant star. Even if he traveled his whole life, he would have to move faster than the speed of light. Nothing can move that fast except light itself.
Strange things happen to an object when it moves rapidly. The object weighs more. An object moving at 86 percent of the speed of light is twice as heavy as it is at rest. A stick appears shorter. A clock runs more slowly. A man would not age so fast as he would on the earth.
Light travels more than 186, 000 miles a second, or about 11 million miles a minute. In one year, light travels six trillion(万亿) miles. That great distance is called a light-year. It is used to measure distances in space.
The star closest to our sun is Alpha Centrauri (半人马座a星). It is more than four lightyears away. If one traveled at the speed of light, he could make a round trip to Alpha Centauri in nine years. But, even at that speed, he could not reach Alcaid (北斗星)in the handle of the Big Dipper. A one-way journey to Alcaid would take almost 200 years!
Why do we measure the distance in light-years instead of miles？
A．Units of light-years sound better.
B．Using light-years reduced the number of figures used.
C．We used to measure distance in light-years long ago.
D．We do not make mistakes when we use light-years.
第8题
The main trouble is that our neighbor worlds, the bodies in the Solar system appear to be unsuitable for advanced life-forms. The Moon may be ruled out at once; it has hardly any atmosphere. Venus(金星) is little better; the surface temperature is extremely high and the atmosphere is mostly carbon dioxide. Mars with a very thin atmosphere and a severe shortage of water, may well support simple plant life but there seems no hope of finding animals, while the attractive Martians(火星人) of the story-tellers have long since been given up.
Of course this has not stopped the flow of bright ideas for communicating with the supposed people on Mars. In the early nineteenth century the great mathematician Gauss suggested planting treepatterns in Siberia(西伯利亚), so that the Martians would see them and replay suitably. Following up this idea, the Austrian scientist Karl Littrow proposed digging very wide ditches in the Sahara, triangular in patterns, and then filling them with petrol or some substance so that, when lit, the ditches would present Martian observers with a "flaming triangle" which would show the existence here of intelligent minds. Even better were the plans of Charles Cross, a French writer of the 1870's, who wanted to build a large mirror to reflect the sun's rays and concentrate them on the surface of Mars, thereby making a vast burning-glass. By swinging the mirror around, Cross explained it would be practicable to write words in the Martian deserts simply by burning the sand. For many years he bombared(轰击) the French government with literature about this plan and was very disappointed when no official interest was shown.
The opinion of the writer is that ______.
A．there may be other intelligent beings in the universe
B．there are other intelligent beings in the universe
C．people living on the earth are almost certainly the only intelligent beings in the universe
D．people living on the earth are definitely the only intelligent beings in the universe
第9题
听力原文： Thank you for coming here today—I hope you're all enjoying the lunch. As you know, we're here to celebrate with Mr. Kim, who is retiring after 37 years with New Star Corporation. When he started here as an inexperienced university graduate, he had no idea that he would be president of the company one day. But he never stopped trying to improve things. With great persistence— he never gave up—he worked his way up to become the company's leader. Even in this last year of his service to New Star, Mr. Kim initiated a market research study to reevaluate our company's performance and ensure its continued profitability. On a very personal level, I believe Mr. Kim has inspired each one of us with his wisdom, fairness and empathy towards all staff from board members to our newest recruits. Please join me in wishing Mr. Kim a fond farewell.
What is the purpose of the luncheon？
A．To discuss business strategies
B．To welcome new staff
C．To honor a colleague
D．To conduct market research
第10题
听力原文：W: The Tan Film Festival is coming to Bellville next month. I can't believe it!
M: Does that mean that all the big stars will make their appearance here？
W: That's exactly what it means. I am so excited. I'm going to put in my request for a holiday during that time and see every movie they're going to show. I'm also going to get the signatures of every star I know. Would you like to join me？
M: I wish I could, but I won't be here next month. The company is sending me to our head office in London for the annual managerial training for a week.
When is the film festival scheduled to start？
A．This week.
B．Next week.
C．Next month.
D．In two months.
第11题
Black Holes
1 Black holes can be best described as a sort of vacuum, sucking up everything in space. Scientists have discovered that black holes come from an explosion of huge stars. Stars that are near death can no longer burn due to loss of fuel, and because its temperature can no longer control the gravitational(重力的) force, hydrogen ends up putting pressure onto the star’s surface until it suddenly explodes then collapses.
2 Black holes come from stars that are made of hydrogen, other gases and a few metals. When these explode it can turn into a stellar-mass(恒星质量) black hole, which can only occur if the star is large enough (should be bigger than the sun) for the explosion to break it into pieces, and the gravity starts to compact every piece into the tiniest particle. Try to see and compare: if a star that’s ten times the size of the sun end up being a black hole that’s no longer than 70 kilometers, then the Earth would become black hole that’s only a fraction of an inch!
3 Objects that get sucked in a black hole will always remain there, never to break free. But remember that black holes can only gobble up(吞噬) objects within a specific distance to it. It’s possible for a large star near the sun to become a black hole, but the sun will continue to stay in place. Orbits(轨道) do not change because the newly formed black hole contains exactly the same amount of mass as when it was a star, only this its mass is totally contracted that it can end up as no bigger than a state.
4 So far, astronomers have figured out that black holes exist because of Albert Einstein’s theory of relativity. In the end, through numerous studies, they have discovered that black holes truly exist. Since black holes trap light and do not give off light, it is not possible to detect black holes via a telescope. But astronomers continue to explore galaxies(银河系), space and the solar system to understand how black holes. It is possible that black holes can exist for millions of years, and later contribute further process in galaxies, which can eventually lead to creation of new entities. Scientists also credit black holes as helpful in learning how galaxies began to form.
A Is there proof that black holes really exist？
B What are different types of black holes？
C How are black holes formed？
D How were black holes named？
E What happened to the objects around a black hole？
F What are black holes made of？
23 Paragraph 1________
