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
The collapse of the Earth’s magnetic field-which guards the planet and guides many of its creatures-appears to have started abou
The collapse of the Earth’s magnetic field-which guards the planet and guides many of its creatures-appears to have started abou
admin
2012-05-18
48
问题
The collapse of the Earth’s magnetic field-which guards the planet and guides many of its creatures-appears to have started about 150 years ago, the New York Times reported last week.
The field’s strength has decreased by 10 or 15 percent 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 (极). The transition would take thousands of years. Once completed,compass needles that had pointed north would point south. Areversal could cause problems for both man and animals. Birds,fish,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 how satellites called Swarm are 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 geophyslcist working on the satellite plan. "I’m personally quite convinced we shbutd 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 with changes in the disorderly flows of melted iron,which they see as similar to the gases that make up the clouds of Jupiter.
According to the passage, the Earth’ s magnetic field has______.
选项
A、misguided many a man and animals
B、begun to Change to it’s opposite direction
C、caused the changes on the polarities
D、been weakening it’s strength for a long time
答案
B
解析
本题考查考生的理解能力,根据原文内容“During a reversal,the main field weakens, almost vanishes,and reappears with opposite polarity.”在反向运转时,主要的磁场就会减弱,几乎彻底消失,甚至重新出现相反的磁极。根据这句话可以知道,地球磁场开始向它的反方向改变,所以B比较符合题意。
转载请注明原文地址:https://kaotiyun.com/show/5WnO777K
0
考博英语
相关试题推荐
Americanshadalwaysbeenpreoccupiedwithreformingtheirsociety,with"makingitover,"andbetweenthe1890sandtheendof
ItisincongruousthatthenumberofBritishinstitutionsofferingMBAcoursesshouldhavegrownby254percentduringaperiodw
Influenzashouldnotbedismissedasatrivialdisease.Itkillsthousandsofpeopleeveryyearataveryhighcosttotheecono
Asthecityhasbecomeincreasingly______andpolluted,therehasbeenagrowingrealizationthatcertainactionisurgentlyne
Since1975advocatesofhumanetreatmentofanimalshavebroadenedtheirgoalstoopposetheuseofanimalsforfur,leather,wo
"Theysaidwhatwealwaysknew,"saidanadministrationsource,______.
Youmustalwaysbereadytosacrifice______toduty.
Microwavesareatypeofelectromagneticradiation;theyareaverymildformofelectricalormagneticwavethatmovesthrough
如果你着手干一番事业而失败了,不要丧失信心。”我失败了三次”与”我是一个失败者”之间有着天壤之别。只要你对自己不持否定的想法,不把自己与失败等同起来,而是试图从失败中吸取教训,你很可能在未来取得成功。
1.杰里(Jerry)对日光浴和游泳已经感到厌倦。他想潜入海底去看看,想同其他孩子一起玩。但是,他又觉得他不应该撇下他寡居的母亲。母亲对儿子也是体贴入微,既想让他呆在比较安全的海滩,身边有她照应,又惟恐儿子感到母亲想把他留在身边,对儿子有占有欲。儿子已经1
随机试题
Inspiteofaproblemwiththefaultyequipment,someveryusefulworkwasaccomplished.
患者,双前臂、双手背红斑基础上散在粟粒大小丘疹、丘疱疹及点状糜烂面,有明显浆液性渗出,边界不清,皮疹对称分布,自觉瘙痒剧烈
Wiesel法染嗜铬细胞的结果是
流水作业要素中的工艺参数N与空间参数M之间的关系必须是()。
用于拦洪、调节水位的水闸称为()。
( )编码在编码时并不是针对某一项管理工作而编制的。
单位内部会计监督与政府监督、社会监督的主要区别表现为()。
B2B,是企业与企业之间通过互联网进行产品、服务及信息的交换。交易的供需双方都是商家(或企业、公司),他们使用了Internet的技术或各种商务网络平台,完成商务交易的过程。根据上述定义,下列属于B2B的是()。
Afterconcludingthenegotiations,theCEOsfromthetwoelectronicsmanufacturersareexpectedto______theirpartnershipatap
ReadthetextbelowabouttheU.S.economy.Inmostofthelines41-52thereisoneextraword.Itiseithergrammaticallyinc
最新回复
(
0
)