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
76
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 transition of the Earth’s magnetic field is possibly caused by ______.
选项
A、the flows of melted iron inside the Earth
B、the periodical movement of the Earth
C、the mechanical energy of the solar system
D、the force corning from outer space
答案
A
解析
文章最后一段:谁也不能准确地知道为什么地球磁场会周期性转换,但是科学家说其原因可能在于地壳中融化了的铁的无序流动,它们看起来就像木星上组成云的气体一样。
转载请注明原文地址:https://kaotiyun.com/show/AOmi777K
0
在职申硕(同等学力)英语
相关试题推荐
Insteadofansweringthequestion,themanager______hisshouldersasifitwerenotimportant.
Shouldeitherofthesesituationsoccur,wrongcontrolactionsmightbetakenandapotentialaccidentsequenceinitiated.
Tennessee’spopulationisnearlytwo-fifthsrural,andnosinglecityorgroupofcities______thestate.
Whywasthehydraulicfuelpumpsealimportantforthespaceshuttle?WhichofthefollowingisNOTTRUEaccordingtowhatVoss
Theschoolarrangedroadtripappearsto______thespringbreak.
Man:Youknowwhat?Youshouldinvestthemoneyyourself.Woman:Thathadcrossedmymind.Question:Whatdoesthewomanmean?
A:ItisnotlikeGeorgetobelateforanappointment.B:______He’salwayspunctual
Althoughinteriordesignhasexistedsincethebeginningofarchitecture,itsdevelopmentintoaspecializedfieldisreallyqui
Ihaveaninfatuation(迷恋)withautumn.Thecolorsoftheseason,andthesmells,havealwaysthrilledme.Ihavealwaysfoundjoy
ThecollapseoftheEarth’smagneticfield—whichguardstheplanetandguidesmanyofitscreatures—appearstohavestartedseri
随机试题
分布于上肢内侧后缘的经脉是
丰润有限责任公司未按照规定期限缴纳税款,当地税务局即下达通知,限期缴纳,期满后,该公司仍未缴纳税款。请回答下列问题:税务局限期缴纳的期限不得超过()日。
通常采取的控制库存的方法包括()。
下列关于建设项目投资风险分析的描述,正确的是( )。
根据企业所得税法的规定,下列收人中可以免征企业所得税的是()。
______学说作为最早的一个认知性学习理论,肯定了主体的能动作用,把学习视为个体主动构造完形的过程,强调观察、顿悟和理解等认知功能在学习中的重要作用。
有一个自以为是全才的年轻人,毕业以后屡次碰壁,一直找不到理想的工作,他觉得自己怀才不遇,对社会感到非常失望。多次的碰壁工作,让他伤心而绝望,他感到没有伯乐来赏识他这匹“千里马”。痛苦绝望之下,有一天,他来到大海边,打算就此结束自己的生命。
Themanwalkedslowly(31)thedesertedbeach,hisheaddownandhiseyessearchingthewetsands.Overheadbirds(32)inwidec
WhichofthefollowingcanbeinferredfromthePara1?Wecanlearnfromthesecondparagraphthat______.
A、Themanshouldbuyadifferentmealticketeachmonth.B、Individualseatdifferentamounts.C、Buyingthemealticketwon’tsav
最新回复
(
0
)