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
25
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、after
B、before
C、since
D、when
答案
A
解析
转载请注明原文地址:https://kaotiyun.com/show/DxLd777K
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
Theclothesapersonwearsmayexpresshisstandingorsocialposition.
Children’sNumericalSkillsPeopleappeartobeborntocompute.Thenumericalskillsofchildrendevelopsoearlyandsoin
Icebergs1Icebergsareamongnature’smostspectacular(壮观的)creations,andyetmostpeoplehaveneverseenone.Avagueairo
Icebergs1Icebergsareamongnature’smostspectacular(壮观的)creations,andyetmostpeoplehaveneverseenone.Avagueairo
HeatandHealthExtremelyhotweatheriscommoninmanypartsoftheworld.Althoughhotweatherjustmakesmostpeoplehot,
HeatandHealthExtremelyhotweatheriscommoninmanypartsoftheworld.Althoughhotweatherjustmakesmostpeoplehot,
HeatandHealthExtremelyhotweatheriscommoninmanypartsoftheworld.Althoughhotweatherjustmakesmostpeoplehot,
AnObservationandanExplanationItisworthlookingatoneortwoaspectsofthewayamotherbehavestowardsherbaby.The
AnObservationandanExplanationItisworthlookingatoneortwoaspectsofthewayamotherbehavestowardsherbaby.The
AnObservationandanExplanationItisworthlookingatoneortwoaspectsofthewayamotherbehavestowardsherbaby.The
随机试题
最常见的单性局域网类型有三种:总线型、环型和()。
《瀛涯胜览》
分层抽样
自然人因战争下落不明,从战争结束之日起满2年的,对他可以申请死亡宣告。()
室上性心动过速的心电图特点为()。
使用抗组胺药时的注意事项包括()。
建设工程开工时间是指工程设计文件中规定的任何一项永久性工程的()开始日期。
表面平整光滑,坚固耐用,色彩鲜艳,易清洁、防水、防火、耐磨、耐腐蚀等这种砖称()。
基金对投资的最低限额要求不高,投资者可以。根据自己的经济能力决定购买数量。()
Familiesinalmosteverycountryarechanging.InNorthAfrica,inthepast,manypeoplelivedinextendedfamilies.Fiftytoa
最新回复
(
0
)