VOA慢速英语20060425b
时间:2019-01-30 作者:英语课 分类:2006年慢速英语(四)月
SCIENCE IN THE NEWS - Signs of Water on Saturn 1 Moon Enceladus; Next Close Look Set for 2008By Brianna Blake, Mario Ritter and Cynthia Kirk
Broadcast: Tuesday, April 25, 2006
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This is SCIENCE IN THE NEWS in VOA Special English. I'm Bob Doughty 2.
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And I'm Pat Bodnar. This week: Evidence of water on one of the moons of Saturn ...
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Meet Erketu ellisoni, a newly identified dinosaur 3 ...
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And warnings about the danger of hearing loss from personal music players.
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Life on Earth requires water. When scientists look for life in other places, they look for signs of water. And they now say they have found them on a moon of Saturn.
Saturn and Cassini, an artist's version
The American spacecraft Cassini passed close to Enceladus [en-SELL-ah-dus] in February of two thousand five. Cassini captured images of what appears to be material shooting away from the moon.
The leader of the team studying the pictures of Enceladus is Carolyn Porco of the Space Science Institute in Boulder 4, Colorado. She says the finding could change the way scientists look at conditions for life in the solar system.
Scientists considered several possible causes for the jet of material seen in the pictures from Cassini. But they found the most likely was that water was shooting out of Enceladus. They describe these jets as geysers, just like the boiling water that shoots out of the ground in places like Yellowstone National Park.
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The main difference between Yellowstone's geysers and those of Enceladus is temperature. Geysers on Earth are caused by heat below the ground. Ground water enters these areas, begins to heat and shoots through openings in the ground.
Scientists believe the geysers on Enceladus are only about zero degrees Celsius 5 -- just above freezing. This may seem cold to us. But on Saturn's icy moon, zero degrees is very hot.
Scientific measurements show that Enceladus is very cold -- about two hundred degrees below the freezing point of water. But measurements by Cassini have shown that some parts of Enceladus are much warmer -- only one hundred sixty-degrees below freezing.
Scientists suggest that even warmer temperatures may exist below the surface of the moon. If there is liquid water, it would be much warmer than the surrounding ice. This could cause the liquid water to explode out of openings in the surface, causing the picture that Cassini captured.
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How could water exist on such a cold world? Planetary scientists have developed theories that liquid oceans exist on several icy worlds. Two moons orbiting the planet Jupiter 6, Callisto and Europa, are good candidates.
Information gathered by the Voyager and Galileo space vehicles suggests that powerful forces are at work under the surfaces of these moons. The strong force of gravity from Jupiter may make underground temperatures on Callisto and Europa warm enough to melt water.
But there is a closer example of liquid water hidden under ice right here on Earth. Ten years ago, Russian and British scientists confirmed the existence of a lake in the coldest part of the world -- Antarctica. It is called Lake Vostok. It lies under four thousand meters of ice.
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There are several theories for why water in the lake remains 7 liquid. One is that warmth from the Earth has melted the ice. Another is that pressure from the huge weight above the ice caused it to melt. Whatever the reason, Lake Vostok has led some scientists to believe some moons of Jupiter and now Saturn could have whole oceans hidden under their icy surface.
Cassini will get another close look at Enceladus in two thousand eight.
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You are listening to SCIENCE IN THE NEWS in VOA Special English from Washington.
VOICE ONE:
Scientists say they recently identified a new kind of dinosaur. The dinosaur belongs to the group of plant-eating creatures called sauropods. These creatures were among the largest land animals that ever lived.
Erketu ellisoni
The scientists have named the dinosaur Erketu [er-KEE-tu] ellisoni. They say its neck was more than seven meters long. But what makes Erketu ellisoni so special is the length of the neck when compared to its body. The scientists estimate the body was about three and one-half meters tall. That means the neck was probably more than two times as long as the rest of the body.
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The dinosaur's remains were found four years ago in the Gobi Desert of Mongolia. Two research scientists from the American Museum of Natural History in New York made the discovery. They described the remains in a report published in Novitates, the museum magazine.
In total, the researchers found a chest bone, two leg bones, an anklebone and several neck bones. Mark Norell said the dinosaur's secret to moving with such a long neck is found in its unusual bones. He said the bones within the neck were large but full of air holes. This made the bones very strong, while at the same time, very light.
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The researchers believe the ancient animal did not hold its neck up high in the air. Instead, they believe the neck was held out in front of the body and level with the ground.
Erketa ellisoni appears to be similar to other members of the sauropod group Titanosauria. These creatures spread throughout the world and survived until the end of the Cretaceous Period, when dinosaurs 8 died off. The Cretaceous Period ended about sixty-five million years ago.
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How loud do you listen to music?
Researchers from Zogby International did a study for the American Speech-Language-Hearing Association. It involved three hundred high school students and one thousand adults. They were asked about their use of portable 9 music players like the Apple iPod. Other popular devices are CD players and laptop computers.
Forty percent of students and adults said they set the sound levels, or volume, at high on their iPods. But students were two times more likely to play the music at a very loud volume. More than half of the students said they would probably not limit their listening time. And about a third said they were not likely to reduce the volume.
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The study found that more than half of the students and less than forty percent of the adults had at least one kind of hearing loss. Some reported difficulty hearing parts of a discussion between two people. Others said they had to raise volume controls on a television or radio to hear it better. And, some experienced ringing in their ears or other noises.
Hearing experts say part of the problem is the listening equipment people are using. They say large earphones that cover the whole ear are probably safer than the smaller earbuds that come with most music players. Earbuds are thought to be less effective than earphones in blocking out foreign noises.
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Hearing loss may not be apparent 10 for years. But once it happens, it is permanent. About thirty million Americans have some hearing loss. One third of them lost their hearing as a result of loud noises.
Experts at the Mayo Clinic in Minnesota say any sound above ninety decibels 11 for long periods may cause some hearing loss. But most portable music players can produce sounds up to one hundred twenty decibels.
The American Speech-Language-Hearing Association is working with manufacturers and government officials on setting rules for use of portable music devices. The group says the best way to protect your hearing is to reduce the volume, limit listening time and using earphones that block out foreign noises.
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On March twenty-ninth Apple Computer announced a way for users to set a personal volume limit on the iPod Nano and fifth-generation iPod. It requires a free download of a software update from the company's Web site. Parents can also use the software to enforce a volume limit on their children's iPod with a secret combination code.
The iPod came on the market in October of two thousand one. Apple has sold more than forty million.
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SCIENCE IN THE NEWS was written by Mario Ritter, Brianna Blake and Cynthia Kirk, who also produced our program. I'm Pat Bodnar.
VOICE ONE:
And I'm Bob Doughty. You can read and listen to our programs at www.unsv.com. To send us e-mail, write to special@voanews.com. And we hope you listen again next week for more news about science, in Special English, on the Voice of America.
- Astronomers used to ask why only Saturn has rings.天文学家们过去一直感到奇怪,为什么只有土星有光环。
- These comparisons suggested that Saturn is made of lighter materials.这些比较告诉我们,土星由较轻的物质构成。
- Most of successful men have the characteristics of contumacy and doughty.绝大多数成功人士都有共同的特质:脾气倔强,性格刚强。
- The doughty old man battled his illness with fierce determination.坚强的老人用巨大毅力与疾病作斗争。
- Are you trying to tell me that David was attacked by a dinosaur?你是想要告诉我大卫被一支恐龙所攻击?
- He stared at the faithful miniature of the dinosaur.他凝视著精确的恐龙缩小模型。
- We all heaved together and removed the boulder.大家一齐用劲,把大石头搬开了。
- He stepped clear of the boulder.他从大石头后面走了出来。
- The temperature tonight will fall to seven degrees Celsius.今晚气温将下降到七摄氏度。
- The maximum temperature in July may be 36 degrees Celsius.七月份最高温度可能达到36摄氏度。
- Jupiter is unlike the Earth in almost every way.木星与地球几乎完全不同。
- The astronomers were taking an observation of Jupiter.天文学家们正在观测木星。
- He ate the remains of food hungrily.他狼吞虎咽地吃剩余的食物。
- The remains of the meal were fed to the dog.残羹剩饭喂狗了。
- The brontosaurus was one of the largest of all dinosaurs. 雷龙是所有恐龙中最大的一种。 来自《简明英汉词典》
- Dinosaurs have been extinct for millions of years. 恐龙绝种已有几百万年了。 来自《简明英汉词典》
- I have a portable typewriter.我有一个便携式打字机。
- There is a pretty portable pair of steps in one corner of the room.屋角放着一架小巧玲珑的折梯。
- The apparent truth was really a lie.表面上看似实话,实际上是个谎言。
- His guilt is apparent to all.他的罪恶尽人皆知。