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
For more than thirty years scientists have been searching for signs of life on other planets. Most of these searches have been d
For more than thirty years scientists have been searching for signs of life on other planets. Most of these searches have been d
admin
2010-01-12
35
问题
For more than thirty years scientists have been searching for signs of life on other planets. Most of these searches have been done over the radio. The hope is that someone in outer space may be trying to get in touch with us. Scientists also have sent radio and television messages, as well as messages on spaceships traveling through space, on the chance that someone may be receptive to such messages.
Scientists are using powerful radio telescopes to "listen" to signals from about 1,000 stars, all within 100 light years of the earth. In addition, they will scan the entire sky to listen for radio messages from more distant stars. Using a computer, they will be able to monitor more than eight million channels at a time. Scientists are looking for any signal that stands out from the background noise.
Of the 200 billion stars in the Milky Way galaxy, scientists find that five percent of the stars are like our sun. Perhaps half of them have a planet like the earth. Such a planet would be a reasonable distance from the star for the temperatures to be right for the evolution of life. Believing that there are the inhabitable (that can be lived in) planets in our galaxy, most scientists agree that chances are that one or more of these planets support some life.
However, many scientists wonder whether intelligent life exists on other planets. Some believe that thirty years of searching without any intelligent messages show that no one is out there. They say that the evolution of intelligence comparable to ours is unlikely.
(44) Other scientists believe that our search hasn’t been long enough to rule out the possibility that intelligent life exists in our galaxy. Although our sun family is only about five billion years old, our galaxy is about 20 billion years old. In that time some scientists think it is likely that civilizations are much more advanced than ours. Perhaps these civilizations send us no signals; perhaps we have not recognized the signals they have sent us. If we hope to find intelligent life, these scientists believe that we have to keep looking.
According to the passage, how many planets in our galaxy might be inhabitable?
选项
A、5 billion
B、10 billion
C、15 billion
D、200 billion
答案
A
解析
转载请注明原文地址:https://kaotiyun.com/show/zLJO777K
0
成人本科学位英语
相关试题推荐
I’mkeepingmy______open;Ihavenotmadeadecisiononthismatter.
ItissaidthatinEnglanddeathispressing,inCanadainevitableandinCaliforniaoptional.Smallwonder.Americans’lifeexp
Pricesoffoodandclothingandalmosteverythingelseinthecountryhavesteadilygoneup.Asaresult,thebuying______ofthe
Duringrecentyearswehaveheardmuchabout"race":howthisracedoescertainthingsandthatracebelievescertainthingsand
Whenthemancamein,carryingthemachinegun,mostofuslookedupinsurprise,becausewe______anythinglikeitbefore.
Theresearchscientistsoftenmeetwithproblems______newtypesofinstrumentfortheirsolution.
Withthepossibleexceptionofequalrights,perhapsthemostcontroversialissueacrosstheUnitedStatestodayisthedeathpe
Thereareplacesintheworldwherepeoplearealleged(被认为)tolivemuchlongerandremainmorevigorousinoldagethaninmos
Cyberspace(网络空间),datasuperhighways,multimedia—forthosewhohaveseenthefuture,thelinkingofcomputers,televisionand
Onlyintimesofgreatcrisis______themajorityofAmericansdemandthattheirrepresentativesseekboldsolutiontobasicprobl
随机试题
鹿茸的日用量是
角钢的中性层位于角钢的________处。
等速送丝埋弧焊主要应用于()电流密度的焊接。
国家统计局科学研究所课题组提出的中国可持续发展指标体系包括的领域有()
A.责令暂停六个月以上一年以下执业活动B.吊销其执业证书C.追究刑事责任D.罚款E.承担赔偿责任
王羲之书法所表现出的那种姿韵萧散、超然于物外的雅逸之风,一直是后代书法家极力追摹的理想境界。王羲之的书法从容自得、真率烂漫,没有一点尘埃气的风流神韵,散发着当时的时代趣味,展示了当时士人向外发现了自然、向内发现了自我的自信和超逸,成为引领这一书风的代表。最
甲唆使乙杀丙,乙将丙杀死。甲和乙属于()。
域名采用分层次的命名方法。com是一个顶级域名,它代表【 】。
首先将order_detail表全部内容复制到od_bak表,然后完成如下操作:(1)将od_bak表中的订单号字段值只保留最后一个字母(用REPLACE命令或SQLUPDATE命令完成修改)。(2)用SQL语句对odbak表编写完成
A、Heansweredallherquestionscorrectly.B、Hereceivedagoodgradeincookingclass.C、Shelikeswhathehasjustcooked.D、S
最新回复
(
0
)