Unless we spend money to spot and prevent asteroids(小行星) now, one might crash into Earth and destroy life as we know it, say some scientists.
Asteroids are bigger versions of the meteoroids(流星)that race across the night sky. Most orbit the sun far from Earth and don't threaten us. But there are also thousands whose orbits put them on a collision course with Earth.
Buy $40 million worth of new telescopes right now. Then spend $10 million a year for the next 25 years to locate most of the space rocks. By the time we spot a fatal one, the scientists say, we'll have a way to change its course.
Some scientists favor pushing asteroids off course with nuclear weapons. But the cost wouldn't be cheap.
Is it worth it? Two things experts consider when judging any risk are: 1) How likely the event is; and 2) How bad the consequences if the event occurs. Experts think an asteroid big enough to destroy lots of life might strike Earth once every 400,000 years. Sounds pretty rare-but if one did fall, it would be the end of the world. "If we don't take care of these big asteroids, they'll take care of us", says one scientist. "It's that simple".
The cure, though, might be worse than the disease. Do we really want fleets of nuclear weapons sitting around on Earth? "The world has less to fear from doomsday(毁灭性的) rocks than from a great nuclear fleet set against them, "said a New York Times article.
What does the passage say about asteroids and meteoroids?
A.They are heavenly bodies different in composition.
B.They are heavenly bodies similar in nature.
C.There are more asteroids than meteoroids.
D.Asteroids are more mysterious than meteoroids.
第1题
恶性多形性腺瘤临床表现不包括
A.多见于60岁以上的老年人
B.生长迅速
C.肿瘤时大时小,有消长史
D.局部有疼痛与麻木感
E.肿物固定,不能移动
第2题
恶性多形性腺瘤临床表现不包括
A.多见于60岁以上的老年人
B.生长迅速
C.肿瘤时大时小,有消长史
D.局部有疼痛与麻木感
E.肿物固定,不能移动
第4题
外阴纤维瘤的临床表现是
A.多个肿块,多发生于阴唇
B.生长缓慢、质软,位于皮下组织内,呈圆形分叶状
C.多见于大阴唇,肿瘤表面可有溃疡和坏死
D.生长迅速,肿瘤包膜完整,与表皮不粘连
E.肿物有蒂或突出于皮肤表面、质硬、光滑
第6题
多见于老年人面部,生长缓慢。浸润破坏深层组织,很少发生转移,对放疗敏感的肿瘤是
A.黑色素瘤
B.基底细胞癌
C.蕈样霉菌病
D.恶性色素痣
第7题
老年人的患病特点不包括
A.诊断困难
B.并发症多
C.临床表现典型
D.恶化迅速
E.多种疾病集于一身
第8题
老年人的患病特点不包括
A.诊断困难
B.并发症多
C.临床表现典型
D.恶化迅速
E.多种疾病集于一身
第9题
下列有关急性小肠扭转临床表现的描述中,错误的是
A.多见于老年人
B.多发生于饱餐后剧烈活动时
C.起病急剧,腹痛剧烈
D.频繁呕吐
E.可出现休克
第10题
下列哪项不是基底细胞腺瘤的临床表现
A.肿瘤生长缓慢,无痛
B.多表现为坚实的黏膜下结节,界限清楚,可移动
C.主要发生于腮腺
D.多见于60~70岁,男女发病之比为1:2
E.有面神经麻痹现象
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