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
考研
The collapse of the Earth’s magnetic field—which guards the planet and guides many of its creatures—appears to have started seri
The collapse of the Earth’s magnetic field—which guards the planet and guides many of its creatures—appears to have started seri
admin
2012-02-27
91
问题
The collapse of the Earth’s magnetic field—which guards the planet and guides many of its creatures—appears to have started seriously about 150 years ago, the New York Times reported last week.
The field’s strength has decreased by 10 or 15 per cent so far and this has increased the debate over whether it signals a reversal of the planet’s lines of magnetic force.
During a reversal, the main field weakens, almost vanishes, and reappears with opposite polarity. The transition would take thousands of years. Once completed, compass needles that had pointed north would point south. A reversal could cause problems for both man and animals. Astronauts and satellites would have difficulties. Birds, fish and animals that rely on the magnetic field for navigation would find migration confusing. But experts said the effects would not be a big disaster, despite claims of doom and vague evidence of links between past field reversals and species extinctions.
Although a total transition may be hundreds or thousands of years away, the rapid decline in magnetic strength is already affecting satellites. Last month, the European Space Agency approved the world’s largest effort at tracking the field’s shifts. A group of new satellites, called Swarm, is to monitor the collapsing field with far greater precision. "We want to get some idea of how this would evolve in the near future, just like people trying to predict the weather," said Gauthier Hulot, a French geophysicist working on the satellite plan. "I’m personally quite convinced we should be able to work out the first predictions by the end of the mission."
No matter what the new findings, the public has no reason to panic. Even if a transition is coming on its way, it might take 2 000 years to mature. The last one took place 780 000 years ago, when early humans were learning how to make stone tools. Deep inside the Earth flow hot currents of melted iron. This mechanical energy creates electromagnetism. This process is known as the geophysical generator. In a car’s generator, the same principle turns mechanical energy into electricity.
No one knows precisely why the field periodically reverses. But scientists say the responsibility probably lies with changes in the disorderly flows of melted iron, which they see as similar to the gases that make up the clouds of Jupiter.
The author says ". . . the public has no reason to panic" (Paragraph 5) because ______.
选项
A、the transition is still thousands of years away
B、the new transition will come 780 000 years from now
C、the transition can be precisely predicted by scientists
D、the process of the transition will take a very long time to finish
答案
D
解析
见上题。
转载请注明原文地址:https://www.kaotiyun.com/show/8Omi777K
0
在职申硕(同等学力)英语
相关试题推荐
Withtheconstantchangeoftheconditions,theoutcomeisnotalways______.
Investmentinthepublicsector,suchaselectricity,irrigation,publicservicesandtransport(excludingvehicles,shipsandpl
Somepeoplefeelsadaboutglobalizationbecausetheybelieveitwill______Internetwasoriginallydesigned______
Ifthereisonethingscientistshavetohear,itisthatthegameisover.Raisedonthebeliefofanendlessvoyageofdiscove
Recentstudieshaveposedthequestionastowhetherthereisalinkbetweenfilmviolenceandrealviolence.
Thepolicetriedinvaintobreakuptheprotestcrowdsinfrontofthegovernmentbuilding.
Whywasthehydraulicfuelpumpsealimportantforthespaceshuttle?WhichofthefollowingisNOTTRUEaccordingtowhatVoss
Honeyguides,orindicatorbirds,collaboratewithhoneybadgersinseekingoutbeecolonies.
It’snotjustyourimagination.Incitiesfromcoasttocoast,theuseofSpanishisbooming,andisproliferatinginwaysnoot
Tosuppressthisuprisingcompletelyseemedtobetoodifficultamissiontotheseofficials.
随机试题
以下不属于肾小管重吸收功能试验的是A.尿β2-微球蛋白测定B.磷的重吸收率测定C.滤过钠排泄分数测定D.葡萄糖最大重吸收量测定E.酚红排泄试验
好的核素图像应具备的条件,错误的是
腮腺区包块通常不做术前病理检查.而采取手术时做冰冻检查的主要原因是
关于建造师不予注册的说法,正确的是()。
根据我国出口收汇核销制度,企业在向银行结汇时必须提交核销单,否则银行不予核销。()
收购要约约定的收购期限不得少于()日,并不得超过()日。
Cyberspace,datasuperhighways,multi-media——forthosewhohaveseenthefuture,thelinkingofcomputers,televisionandtelephones
ItisgenerallyrecognizedintheworldthatthesecondGulfWarinIraqisacrucialtestofhigh-speedWeb.Fordecades,Ameri
下面说法中正确的是(47)。
(1)在考牛文件灾下有一个工程文件sjt3.vbp。程序的功能是通过键盘输入正整数到文本框中。在“除数”框架中选择一个单选按钮,然后单击“处理数据”命令按钮,将大于文本框中的正整数,并且能够被所选除数整除的5个数添加到列表框List1中,如图所示。在窗体文
最新回复
(
0
)