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
"My own feelings went from disbelief to excitement to downright fear", says Carl Hergenrother, 23, an Arizona undergraduate who
"My own feelings went from disbelief to excitement to downright fear", says Carl Hergenrother, 23, an Arizona undergraduate who
admin
2013-06-10
30
问题
"My own feelings went from disbelief to excitement to downright fear", says Carl Hergenrother, 23, an Arizona undergraduate who verified a large asteroid barreling toward Earth with a 230cm telescope atop nearby Kitt Peak. "It was scary, because there was the possibility that we were confirming the demise of some city somewhere, or some state or small country".
Well, not quite. Early last week, his celestial interloper whizzed by Earth, missing the planet by 450620 km—a hairbreadth in astronomical terms. Perhaps half a kilometer across, it was the largest object ever observed to pass that close to Earth.
Duncan Steel, an Australian astronomer, has calculated that if the asteroid had struck Earth, it would have hit at some 93450 km/h. The resulting explosion, scientists estimate, would have been in the 3000-to-12000-megaton range. That, says astronomer Eugene Shoemaker, a pioneer asteroid and comet hunter, "is like taking all of the U.S. and Soviet nuclear weapons, putting them in one pile and blowing them all up".
And what if one them is found to be on a collision course with Earth? Scientists at the national laboratories at Livermore, California, and Los Alamos, New Mexico, have devised a number of ingenious plans that, given enough warning time, could protect Earth from a threatening NEO. Their defensive weapons of choice include long-distance missiles with conventional or, more likely, nuclear warheads that could be used either to nudge an asteroid into a safe orbit or blast it to smithereens.
Many people-including some astronomers—are understandably nervous about putting a standby squadron of nuclear tipped missiles in place. Hence the latest strategy, which in some cases would obviate the need for a nuclear defense: propelling a fusillade of cannonball-size steel spheres at an approaching asteroid. In a high-velocity encounter with a speeding NEO, explains Gregory Canavan, a senior scientist at Los Alamos, "the kinetic energy of the balls would change into heat energy and blow the thing apart".
Some astronomers oppose any immediate defensive preparations, citing the high costs and low odds of a large object’s striking Earth in the coming decades. But at the very least, Shoemaker contends, NEO detection should be accelerated. "There’s this thing called the ’giggle factor’ in Congress", he says, "people in Congress and also at the top level in NASA still don’t take it seriously. But we should move ahead. It’s a matter of prudence".
The world, however, still seems largely unconcerned with the danger posed by large bodies hurtling in from space, despite the spectacle two years ago of Comet Shoemaker-Levy 9 riddling the planet Jupiter with mammoth explosions. It remains to be seen whether last week’s record near-miss has changed any minds.
选项
A、the earth narrowly escaped a catastrophe.
B、one asteroid almost destroyed an entire city.
C、asteroids are comparable to nuclear weapons.
D、the planet earth is vulnerable to dangers.
答案
A
解析
转载请注明原文地址:https://kaotiyun.com/show/eed4777K
0
考研英语一
相关试题推荐
TheauthorseemstobelievethattheSupremeCourt’sdecisionWhichofthefollowingbestdefinestheword"libel"(Paragraph8
WhichofthefollowingisNOTafeatureofyoungpeopleintheearly1980s?Whydoyoungpeoplestresstheimportanceofaheal
About40percentofAmericansthinkofthemselvesasshy,whileonly20percentsaytheyhaveneversufferedfromshynessatsom
Supposeyouareacollegestudentonaschoolcampusoranemployeeinacompany.Recentlyyounoticedthatsomepeopleneverpa
"Sustainability"hasbecomeapopularwordthesedays,buttoTedNing,theconceptwillalwayshavepersonalmeaning.Havingen
Self-esteemisthecollectionofbeliefsorfeelingswehaveaboutourselves,our"self-perceptions."Howwedefineourselvesi
Weakdollarorno,$46,000-thepriceforasingleyearofundergraduateinstructionamidtheredbrickofHarvardYard-is【1】But
MillionsofpeoplepassthroughthegatesofDisney’sentertainmentparksinCalifornia,FloridaandJapaneachyear.Whatmakes
Whatcanbeinferredfromthesentence"it’stheaccountholderwhomaygetburned"(Paragraph1)?Theterm"high-marginbusine
随机试题
下列哪些说法是正确的?()
谵妄的主要特征是
关于白血病发病情况,下列说法错误的是
A.甘露消毒丹B.沙参麦冬汤C.解肌透痧汤D.银翘散E.凉营清气汤丹痧之邪侵肺卫证,治疗宜选
A、热扰心神B、心气大伤,精神散乱C、痰火扰心D、心气虚,精不养神E、风痰上扰独语的病因是
下列关于《节约能源法》说法正确的是()。
由于报警总线开路使火灾报警控制器发出故障,故障指示灯亮,则排除该故障的方法是()。
A公司2016年财务报表主要数据如下表所示:假设A公司资产均为经营资产,流动负债为经营负债,长期负债为有息负债,不变的营业净利率可以涵盖新增债务增加的利息,假设企业各项经营资产、经营负债占营业收入的比不变。要求:如果该公司预计2017年销售增长率
邓小平对社会主义本质所作的概括,一方面强调必须集中力量解放和发展生产力,另一方面指出了解放和发展生产力的手段和目的。它的基本内涵包括()
以下()控件没有Caption属性。
最新回复
(
0
)