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
41
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.
According to Newton’s principle ______.
选项
A、the force of gravity keeps planets orbiting around the sun rather than flying off
B、the sun is the most massive object, making up 99.8 percent of the mass of the solar system
C、the amount of mass determine how fast the objects travel as they orbit each other
D、Pluto receives the least force of gravity from the sun of all the planets in the solar system
答案
D
解析
根据牛顿定律,物质间的引力与距离成反比。在太阳系(solar system),冥王星距太阳最远,受到的引力最小。
转载请注明原文地址:https://kaotiyun.com/show/OGB7777K
0
大学英语六级
相关试题推荐
Althoughthestigma(污名)onceassociatedwithmentalillnesshasrecededinrecentyears,mostofthe12millionAmericanswhoh
Everdippedintothebiscuittinthendecidedyou’veruinedyourdietsoyoumayaswelleatthelot?Orthoughtthatbecauseyo
Everdippedintothebiscuittinthendecidedyou’veruinedyourdietsoyoumayaswelleatthelot?Orthoughtthatbecauseyo
Ifyouareanythinglikeme,youleftthetheaterafterSexandtheCity2andthought,thereoughttobealawagainstalooks-
WehavetheevidencethatAppleisontosomething______(38家苹果店在建,还有更多店在筹建).
Kunzgaveupsoftwareengineeringmainlybecauseheearnedlessthanthoseinlaworbusinessfielddid.Onlyasmallpercentag
Lastyear,ournation’scapitalpassedthemurder-a-daymark,andthenumberofhomicidesisnowupsome50percentfromthatle
A、Itcanincreaseproductionby4.5percentinfactoriesatleast.B、Itissometimesveryboringtotheworkers.C、Itcanpossib
The35percentofAfrican-Americanyouthlivinginpovertyarethemostvisiblevictimsofwhatisoftencalledtheachievement
随机试题
Accordingtothemassage,womenareusuallygoodat______.Allthefollowingtasksinvolvevisual-spatialabilitiesEXCEPT_____
A.广泛小血管炎伴血栓形成B.血管内膜纤维化C.急性间质炎D.急性血管炎慢性排斥反应
艾滋病已成为流行于何处的传染病
天麻钩藤饮主治( )。
下列关于建设项目所在地附近台站气象调查的调查期间说法正确的是( )。
按照《工业金属管道工程施工规范》GB50235——2010,等厚管道安装时,关于对口允许的最大错边量,下列说法正确的是()。
某汽车制造企业属于增值税一般纳税人,生产某种品牌的小轿车,每辆不含税平均销售价格和最高销售价格均为10万元,2016年2月发生如下业务:(1)与某特约经销商签订了40辆小轿车的平销返利协议,协议规定按含税销售额的5%支付返还收入,当月收到经销商返回的30
甲公司是一家汽车制造企业,每年需要M零部件20000个,可以自制或外购。自制时直接材料400元/个,直接人工100元/个,变动制造费用200元/个,固定制造费用150元/个。甲公司有足够的生产能力,如不自制,设备出租可获得年租金400000元。甲公司选择外
读下图,AB直线距离为R(R是地球直径),此时地球公转处于近日点附近,回答问题。若此图是以北极为中心的投影图,则A所处的纬度是()。
条件充分性判断:A.条件(1)充分,但条件(2)不充分B.条件(2)充分,但条件(1)不充分C.条件(1)和(2)单独都不充分,但条件(1)和(2)联合起来充分D.条件(1)充分,条件(2)也充分E.条件(1)和(2)单独都不充分,条件(1)和(
最新回复
(
0
)