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
Mounting evidence has led astronomers to just such an improbable conclusion, at least 90 percent and possibly 99 percent of all
Mounting evidence has led astronomers to just such an improbable conclusion, at least 90 percent and possibly 99 percent of all
admin
2013-05-04
36
问题
Mounting evidence has led astronomers to just such an improbable conclusion, at least 90 percent and possibly 99 percent of all matter in the universe is completely invisible. Astronomers call this invisible stuff dark matter.
An astronomer first reported the invisible matter after noting some unusual behavior in visible matter. In 1993, Swiss astrophysicist Fritz Zwicky observed that galaxies in a cluster of galaxies travelled at higher speeds than expected. He concluded that something was causing strange gravitational effects on these galaxies.
Galaxies are like vast islands in deep space containing billions of stars that are held together by the force of gravity. Some galaxies are part of larger systems called clusters, which contain many galaxies. Most galaxies, however, belong to smaller systems called groups. Groups and clusters in turn form even larger structures known as superclusters. Just as the force of gravity keeps stars together in galaxies, so the force of gravity appears to keep galaxies together in clusters.
This same force of gravity keeps planets orbiting around the sun, rather than flying off into space. How great a force gravity exerts depends on the mass of the objects attracted and the distance between them, a principle discovered by Newton. The amount of mass and the distance between objects also determine how fast the objects travel as they orbit each other. For example, in our solar system, the sun is the most massive object, making up about 99.9 percent of the mass of the solar system, and the force of its gravity keeps Earth and the other planets in orbit around it. The orbital speeds of the planets decline with increasing distance from the sun. The planet nearest to the sun, Mercury, travels at an orbital speed of 48 kilometers per second, while the distant planet Pluto orbits at speed of 4.7 kilometers per second.
We can conclude that this article is intended for ______.
选项
A、general readers
B、scientists
C、students majoring in physics
D、astronomers
答案
A
解析
用排除法解。这是一篇科普性质的文章,读者对象不可能是科学家(从大量名词解释可以看出),也不是针对宇航员的而是关于他们的报道;若是针对物理专业的学生,话题义显得浅显,而且又谈了天文方面的知识,所以只能是一般读者。
转载请注明原文地址:https://kaotiyun.com/show/dGB7777K
0
大学英语六级
相关试题推荐
A、Theythoughtshewastooyoung.B、Theythoughtshewassmallinsize.C、Theythoughtshedidnotplaywellenough.D、Theythou
Althoughthestigma(污名)onceassociatedwithmentalillnesshasrecededinrecentyears,mostofthe12millionAmericanswhoh
Althoughthestigma(污名)onceassociatedwithmentalillnesshasrecededinrecentyears,mostofthe12millionAmericanswhoh
A、Abouthalfofthemareundergraduatestudents.B、About30percentofthemarestudyingEnglish.C、About20percentofthemare
A、Theevidencefoundatthecrimescene.B、Thetestimonyofhistwofriends.C、Thejury’sprejudiceagainsthisrace.D、Thetwo
TheconclusionofanewstudybysociologistsfromtheUniversityofTorontowon’tcomeasasurprisetoworkingwomen:theyfee
TheconclusionofanewstudybysociologistsfromtheUniversityofTorontowon’tcomeasasurprisetoworkingwomen:theyfee
Lastyear,ournation’scapitalpassedthemurder-a-daymark,andthenumberofhomicidesisnowupsome50percentfromthatle
A、Itcanincreaseproductionby4.5percentinfactoriesatleast.B、Itissometimesveryboringtotheworkers.C、Itcanpossib
The35percentofAfrican-Americanyouthlivinginpovertyarethemostvisiblevictimsofwhatisoftencalledtheachievement
随机试题
社会主义核心价值体系是一个有机统一的整体,其中居于灵魂地位的是
感染过程中,血液中最先出现的是()
患者,女性,54岁。发作性剑突下及右上腹绞痛2天,伴寒战。8个月前曾有过类似发作史。查体:体温39℃,脉搏110次/分,血压140/85mmHg。血常规:WBC12×109/L,N0.8,意识清楚,皮肤、巩膜轻度黄染。右肋缘下扪及肿大的胆囊,触痛。治疗
党的十八届四中全会对全面深化改革作出了顶层设计。()
关于民事诉讼中的公开审判制度,下列哪一选项是错误的?
下列描述中,正确的有()。
银行本票可以分为即期银行本票和远期银行本票,在国际商业运算中运用的本票大多是银行本票。()
9月初大学入学报到时,有多家手机运营商到某大学校园进行产品销售宣传。有好几家运营商推出了免费套餐服务。但是其中一家运营商推出了价格优惠的套餐,同时其业务员向学生宣传说:其他运营商所谓的“免费”套餐是通过出售消费者的身份信息来获得运营费用的。以下哪项如果为真
战国初期,上党地区在下列哪一个国家的控制范围之内?()
______werecreatedintheearly1800’sascharitableinstitutionstoprovideasafeplaceforpoorworkingpeopletosaveforr
最新回复
(
0
)