首页
登录
职称英语
Mounting evidence has led astronomers to just such an improbable conclusion,
Mounting evidence has led astronomers to just such an improbable conclusion,
游客
2023-09-01
17
管理
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. [br] 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://tihaiku.com/zcyy/2976593.html
相关试题推荐
[originaltext]Astronomershavespenthundredsofyearssearchingforsigns
[originaltext]Astronomershavespenthundredsofyearssearchingforsigns
[originaltext]Astronomershavespenthundredsofyearssearchingforsigns
Irritatedbythecrimes______(他发誓要出庭作证并说出真相).hesworetogiveevidenceincourt
Mountingevidencehasledastronomerstojustsuchanimprobableconclusion,
Mountingevidencehasledastronomerstojustsuchanimprobableconclusion,
Mountingevidencehasledastronomerstojustsuchanimprobableconclusion,
Whotalksmore,womenormen?Theseeminglycontradictoryevidenceis【C1】___
Whotalksmore,womenormen?Theseeminglycontradictoryevidenceis【C1】___
Whotalksmore,womenormen?Theseeminglycontradictoryevidenceis【C1】___
随机试题
Itseemsindividualcancercellssendoutthesamedistresssignalsaswound
Sofaraswecantell,allhumanlanguagesareequallycompleteandperfect
Janehasjust______aletterfromafriendofhersinEngland.A、returnedB、answer
Forthispart,youareallowed30minutestowriteanessaycommentingononeof
试述护理诊断与医疗诊断的区别。
中央型肺癌最早出现的征象是()A.黏液嵌塞征 B.局限性肺气肿 C.段
与一般的经济计划相比,经济发展战略所具有的特征包括()。A.指令性 B
Auer小体不见于A.M型白血病 B.M型白血病 C.M型白血病 D.急性
单囊型成釉细胞瘤Ⅰ型的组织学特点是A.囊腔衬里上皮基底细胞层细胞核深染 B.
在建设工程项目招标的开标会议上,有权对投标文件密封情况进行检查的主体是()。A.
最新回复
(
0
)