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A black hole is created when a large star burns out. Like our sun, stars are unbelievably hot furnaces (熔炉) that burn their own matter as fuel. When most of the fuel is used up, the star begins to die.
The death of a star is not a quiet event. First there is a huge explosion. As its outer layer is blasted off into space, the dying star shines as brightly as a billion suns.
After the explosion gravity pulls in what’s left of the star. As the outside of the star sinks toward the center, the star gets smaller and smaller. The material the star is made of becomes tightly packed together. A star is so dense that a teaspoon of matter from it weighs billion of pounds.
The more the star shrinks, the stronger the gravity inside it becomes. Soon the star is very tiny, and the gravity pulling it in is unbelievably strong. In fact, the gravity is so strong that it even pulls light into the star! Since all the light is pulled in, none can go out. The star becomes black when there is no light. Then a black hole is born!
That’s what we know about black holes. What we don’t know is this: What happens inside a black hole after the star has been squeezed into a tiny ball? Does it keep getting smaller and smaller forever? Such a possibility is hard to imagine.
But if the black hole doesn’t keep shrinking, what happens to it? Some scientists think black holes are like doorways to another world. They say that as the star disappears from our universe, it goes into another universe. In other words a black hole in our universe could turn into a “white hole” in a different universe. As the black hole swallows light, the white hole shines brightly—somewhere else. But where? A different place, perhaps, or a different time — many years in the past or future.
Could you travel through a black hole? Right now, no. Nothing we know of could go into a black hole without being crushed. So far the time being, black hole must remain a mystery.
Black holes are a mystery—but that hasn’t stopped scientists from dreaming about them. One scientist suggested that in the future we might make use of the power of black holes. They would supply all of Earth’s energy needs, with plenty to spare. Another scientist wondered if a black hole could some day be used to swallow earthly waste—a sort of huge waste disposal(处理) in the sky!
When the star begins to die ______.
A. there is no fuel left in it B. its outer layer goes into space first
C. a huge explosion will happen D. it doesn’t give off light any longer
Which of the following doesn’t help produce a black hole?
A. The gravity inside the star is very strong. B. The light can’t go out of the star.
C. The star becomes smaller and smaller D. The dying star shines very brightly.
The black hole ______.
A. continues becoming smaller and smaller all the time
B. goes into another universe and becomes a white hole
C. can pull in everything we know of in the world
D. will appear at another place at a different time
What’s the best title for this passage?
A. A New Scientific Discovery: Black Holes
B. How Do Black Holes Come Into Being?
C. What Are Black Holes?
D. Travel Through A Black Hole
查看习题详情和答案>>A black hole is created when a large star burns out. Like our sun, stars are unbelievably hot furnaces(熔炉) that burn their own matter as fuel. When most of the fuel is used up, the star begins to die.
The death of a star is not a quiet event. First there is a huge explosion. As its outer layer is blasted off into space, the dying star shines as brightly as a billion suns.
After the explosion gravity pulls in what’s left of the star. As the outside of the star sinks toward the center, the star gets smaller and smaller. The material the star is made of becomes tightly packed together. A star is so dense that a teaspoon of matter from it weighs billion of pounds.
The more the star shrinks, the stronger the gravity inside it becomes. Soon the star is very tiny, and the gravity pulling it in is unbelievably strong. In fact, the gravity is so strong that it even pulls light into the star! Since all the light is pulled in, none can go out. The star becomes black when there is no light. Then a black hole is born!
That’s what we know about black holes. What we don’t know is this: What happens inside a black hole after the star has been squeezed into a tiny ball? Does it keep getting smaller and smaller forever? Such a possibility is hard to imagine.
But if the black hole doesn’t keep shrinking, what happens to it? Some scientists think black holes are like doorways to another world．They say that as the star disappears from our universe, it goes into another universe. In other words a black hole in our universe could turn into a “white hole” in a different universe. As the black hole swallows light, the white hole shines brightly — somewhere else. But where? A different place, perhaps, or a different time — many years in the past or future.
Could you travel through a black hole? Right now, no. Nothing we know of could go into a black hole without being crushed．So far the time being, black hole must remain a mystery.
Black holes are a mystery—but that hasn’t stopped scientists from dreaming about them. One scientist suggested that in the future we might make use of the power of black holes. They would supply all of Earth’s energy needs, with plenty to spare. Another scientist wondered if a black hole could some day be used to swallow earthly waste—a sort of huge waste disposal (处理) in the sky!
When the star begins to die ______.
A．there is no fuel left in it B．its outer layer goes into space first
C．a huge explosion will happen D．it doesn’t give off light any longer
Which of the following doesn’t help produce a black hole?
A．The gravity inside the star is very strong.
B．The light can’t go out of the star.
C．The star becomes smaller and smaller
D．The dying star shines very brightly.
The black hole ______.
A．continues becoming smaller and smaller all the time
B．goes into another universe and becomes a white hole
C．can pull in everything we know of in the world
D．will appear at another place at a different time
What’s the best title for this passage?
A．A New Scientific Discovery: Black Holes
B．How Do Black Holes Come Into Being?
C．What Are Black Holes?
D．Travel Through A Black Hole
查看习题详情和答案>>A new research shows that in Britain more and more people are returning to the old tradition that the whole family have a meal at table. Worrying about the obesity and breakdown of a family, people change their eating habits so greatly, according to analysis. They find the number of the family having a meal together increases by 5% from 2002 to 2004, and most people who have meals with their family come from the rich social class.
The new discovery makes doctors and the people struggling against obesity extremely excited. Giving up the tradition that the whole family have a meal together is exactly one of the reasons for a series of problems including children’s overweight. If a child has a meal in front of the television or the computer alone, he will often eat some fast food.
Jason Collins is one of the persons returning to the old tradition. Collins is a manager of a bake(烘面包) house. He finds after he gets used to having a meal at home with his child, the child becomes much more obedient(听话的). Dr. Jin is a child psychologist, and she expresses welcome to this result of the study. She says it can make parents have a very good chance to chat with the child when the whole family have a meal together.
What makes people change their eating habit back to the old tradition in Britain?
A. Worrying about their children. B. Worrying about some social problems.
C. Worrying about the living expense. D. Worrying about health and family problems.
We can infer from the passage that _______.
A.people’s eating habit has much effect on their family
B. most rich people have meals with their family
C. most children have the problem of overweight
D. most children don’t like having dinner with the parents
How do the people who hope to lose weight feel about the new discovery?
A. They feel glad. B. They feel surprised.
C. They feel sorry. D. They feel disappointed.
Which of the following statements is TRUE according to the passage?
A. The child having dinner with his parents doesn’t like watching TV.
B. Children become overweight all because of having dinner alone.
C. The family having dinner together is more united and friendly.
D. The reason a child has dinner alone is that he likes fast food.
查看习题详情和答案>>A black hole is created when a large star burns out. Like our sun, stars are unbelievably hot furnaces (熔炉) that burn their own matter as fuel. When most of the fuel is used up, the star begins to die.
The death of a star is not a quiet event. First there is a huge explosion. As its outer layer is blasted off into space, the dying star shines as brightly as a billion suns.
After the explosion gravity pulls in what’s left of the star. As the outside of the star sinks toward the center, the star gets smaller and smaller. The material the star is made of becomes tightly packed together. A star is so dense that a teaspoon of matter from it weighs billion of pounds.
The more the star shrinks, the stronger the gravity inside it becomes. Soon the star is very tiny, and the gravity pulling it in is unbelievably strong. In fact, the gravity is so strong that it even pulls light into the star! Since all the light is pulled in, none can go out. The star becomes black when there is no light. Then a black hole is born!
That’s what we know about black holes. What we don’t know is this: What happens inside a black hole after the star has been squeezed into a tiny ball? Does it keep getting smaller and smaller forever? Such a possibility is hard to imagine.
But if the black hole doesn’t keep shrinking, what happens to it? Some scientists think black holes are like doorways to another world. They say that as the star disappears from our universe, it goes into another universe. In other words a black hole in our universe could turn into a “white hole” in a different universe. As the black hole swallows light, the white hole shines brightly—somewhere else. But where? A different place, perhaps, or a different time — many years in the past or future.
Could you travel through a black hole? Right now, no. Nothing we know of could go into a black hole without being crushed. So far the time being, black hole must remain a mystery.
Black holes are a mystery—but that hasn’t stopped scientists from dreaming about them. One scientist suggested that in the future we might make use of the power of black holes. They would supply all of Earth’s energy needs, with plenty to spare. Another scientist wondered if a black hole could some day be used to swallow earthly waste—a sort of huge waste disposal(处理) in the sky!
When the star begins to die ______.
A. there is no fuel left in it B. its outer layer goes into space first
C. a huge explosion will happen D. it doesn’t give off light any longer
Which of the following doesn’t help produce a black hole?
A. The gravity inside the star is very strong. B. The light can’t go out of the star.
C. The star becomes smaller and smaller D. The dying star shines very brightly.
The black hole ______.
A. continues becoming smaller and smaller all the time
B. goes into another universe and becomes a white hole
C. can pull in everything we know of in the world
D. will appear at another place at a different time
What’s the best title for this passage?
A. A New Scientific Discovery: Black Holes
B. How Do Black Holes Come Into Being?
C. What Are Black Holes?
D. Travel Through A Black Hole
查看习题详情和答案>>A super drug that could remove Alzheimer’s (老年痴呆症)，heart disease and diabetes (糖尿病) and help people live to 100 is being developed by scientists. Their research is based on the identification of three genes that help prolong lives and prevent diseases which occur in old age. Medically controlling the proteins made by the “ longevity genes” will allow millions to live longer, predicts Dr Nir Barzilai.
Those whose DNA strongly features the three genes are 80 percent less likely to develop Alzheimer’s. The genes also fight against the deadly impact of smoking, poor diet, obesity and lack of exercise.
Already, several laboratories are working on a pill to imitate the benefits of the genes and Dr Barzilai thinks it could be tested within three years. The pill could remove some diseases that damage old age. “ The advantage of finding a gene that involves longevity is that we can develop a drug that will imitate exactly what this gene is doing,” he said.
Of the three longevity genes, two genes increase the production of so-called good cholesterol(胆固醇), which reduces the risk of heart disease. The third prevents diabetes. They were discovered by Dr Barzilai’s team while studying the DNA of 500 Ashkenazi Jews with an average age of 100. The chances of living that long are one in 10,000 but the group, which shared relatively few common ancestors, was 20 times more likely to hit the entury. Dr Barzilai said: “ 30 percent of them were obese or overweight and 30 percent smoked two acks of cigarettes a day for more than 40 years, however they can live to 100.”
But Andrew Ketteringham of the Alzheimer’s Society said: “Alzheimer’s disease, a most common disease, is likely to be caused by a combination of genetic disosition(遗传倾向), lifestyles and life events. Many genes are probably involved.
Some people are able to live to 100 years because of ______.
A. a magical medicine B. three special genes C. good living habits D. longevity proteins
Why does the discovery of the longevity genes mean a lot?
A. Because it can bring great benefits to scientific labs.
B. Because it can help people change their unhealthy genes
C. Because it helps produce a drug that can make people live longer.
D. Because it will help scientists build up a new branch of biology.
From Paragraph 4 we can infer that ________.
A. longevity genes can create good cholesterol.
B. the volunteers share some common ancestors
C. bad habits are likely to have no effect on the volunteers
D. longevity genes protect the volunteers against bad habits
What is Andrew Ketteringham’s attitude toward the study?
A. Positive B. Negative C. Critical D. Cautious
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