首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
Earth’s Inner Core Scientists have long struggled to understand what lies at the planet’s center. Direct observation of its c
Earth’s Inner Core Scientists have long struggled to understand what lies at the planet’s center. Direct observation of its c
admin
2009-06-15
56
问题
Earth’s Inner Core
Scientists have long struggled to understand what lies at the planet’s center. Direct observation of its center is impossible, so researchers must(51) to other evidence.
In 1889, a German scientist detected a severe earthquake in Japan. Geophysicists concluded that shock waves(52) jolts (晃动)from one side of Earth through the center to the other side. Then in 1936, Danish geophysicist lnge Lehmann studied the waves’(53) to determine that within Earth’s core of molten (熔化了的)iron lies a solid inner core - but(54) that core was made of eluded (难倒)her. Other geophysicists quickly determined that Lehmann’s inner core was composed mostly(55) iron. Since then, Lehmann’s discovery has(56) conventional Earth science.
But now scientists are challenging traditional theory with new and radical(57) . For example, Earth’s center could actually contain an "inner core within the inner core," claim Ishii and colleague Adam Dziewonski.
Analyzing hundreds of thousands of earthquake wave(58) , they maintain that the inner core has at its heart a tiny, even more solid sphere (球体). This sphere "may be the oldest fossil(59) from the formation of Earth," says Dziewonski.
Dziewonski and Ishii speculate that shortly(60) Earth formed around 4.8 billion years ago, a giant asteroid (小行星)smashed into the young planet and nearly melted it. But Earth’s center didn’t quite melt; it(61) mass as the planet cooled. The core within a core may be the kernel (核心)that endured. "its presence could change our basic ideas about the(62) of the planet," Dziewonski says.
Dziewonski’s idea is tame (温和的)compared to the(63) theories of independent geophysicist J. Marvin Herndon. Earth’s inner core is made not of iron, he claims, but a(64) of nickel and silicon. Herndon has a truly revolutionary notion: Within the nickel silicide (硅化物)inner core is also an "inner" inner core - an 8 km-wide ball of the element uranium. Uranium is radioactive. Herndon thinks the uranium releases heat energy as its atoms(65) fission-split and crash into one another in a chain reaction. In other words, we may live on top of a gigantic, "natural" nuclear power plant.
选项
A、charge
B、last
C、experience
D、show
答案
C
解析
转载请注明原文地址:https://kaotiyun.com/show/HxLd777K
本试题收录于:
职称英语理工类A级题库职称英语分类
0
职称英语理工类A级
职称英语
相关试题推荐
Thescientistsbegantoaccumulatedata.
Children’sNumericalSkillsPeopleappeartobeborntocompute.Thenumericalskillsofchildrendevelopsoearlyandsoin
Children’sNumericalSkillsPeopleappeartobeborntocompute.Thenumericalskillsofchildrendevelopsoearlyandsoin
Children’sNumericalSkillsPeopleappeartobeborntocompute.Thenumericalskillsofchildrendevelopsoearlyandsoin
HeatandHealthExtremelyhotweatheriscommoninmanypartsoftheworld.Althoughhotweatherjustmakesmostpeoplehot,
Scottseizedtheopportunitytopresenthisproposaltothedirector.
AnObservationandanExplanationItisworthlookingatoneortwoaspectsofthewayamotherbehavestowardsherbaby.The
AnObservationandanExplanationItisworthlookingatoneortwoaspectsofthewayamotherbehavestowardsherbaby.The
随机试题
在Excel2003中,若F3单元格中的公式为“=C1+$E$2”,则删除A列后,该公式自动调整为________________。
化脓性脑膜炎患儿有颅内压增高、脑疝症状时,首先应予20%甘露醇静脉注射。()
子宫主韧带是防止子宫脱垂的主要结构。
A、IgAB、IgMC、IgDD、IgEE、IgG各类Ig特点分别是:参加CFT反应的
丸剂作为中药传统剂型之一,始载于《五十二病方》,此外,《神农本草经》、《金匮要略》、《太平惠民和剂局方》、《伤寒杂病论》等古典医籍中早有丸剂品种、辅料、剂型理论、制法及应用等方面的记载,丸剂丰富的辅料和包衣材料使其临床应用广泛,如糊丸取其迟化、水丸取其易化
某企业职工小马不喜欢现在的工作,经常出工不出力,多次因工作质量问题与主管领导发生了摩擦,小马想主动解除劳动合同,但又有顾虑,原因是小马在1年前接受企业的安排,到国外参加了专业培训,企业为此支付了4万元培训费用,且小马与企业订立了培训服务期协议和竞业限制协议
浮顶储罐的优点是()。
传唤不需要逮捕、拘留的犯罪嫌疑人的时间一般不得超过()。
鲜花∶塑料花
Recently,yourschoolstudentsareattendingadiscussionwhichisheldbyaEnglishpaper.Themaintopicis:whatkindofteac
最新回复
(
0
)