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
The Cosmological Principle P1: Cosmologists hypothesized that the distribution of matter in the universe is homogeneous and isot
The Cosmological Principle P1: Cosmologists hypothesized that the distribution of matter in the universe is homogeneous and isot
admin
2019-03-10
98
问题
The Cosmological Principle
P1: Cosmologists hypothesized that the distribution of matter in the universe is homogeneous and isotropic when viewed on a large enough scale, since the forces are expected to act uniformly throughout the universe, and should, therefore, produce no observable irregularities on the large scale. This amounts to the strongly philosophical statement that the Passage of the universe which we can see is fair sample, and that the same physical laws apply throughout. In essence, this in a sense says that the universe is knowable and is playing fair with scientists.
P2: In the 1920s, astronomer Edwin Hubble made a groundbreaking discovery that the universe is not static, but rather is expanding. In 1998, the Hubble Space Telescope, named for the astronomer, studied distant supemovae and found that the universe was expanding more slowly a long time ago compared with the pace of its expansion today. But one thing that’s certain is that the expansion of the universe was the primary fact of cosmological significance that cosmological theories had to accommodate. In every direction we look, distant galaxies are moving away from each other. The scientific community was once divided between supporters of two different expanding universe theories: the evolutionary (Big Bang) and the Steady State theory.
P3: The essential idea of evolutionary cosmology is that there was a beginning— a moment of creation at which the universe came into existence in a hot, violent explosion—the Big Bang. Scientists believe that the entire vastness of the observable universe was compressed into a hot, dense mass just a few millimeters across. This nearly incomprehensible state is theorized to have existed for just a fraction of the first second of time. Scientists can’t be sure exactly how the universe evolved after the big bang. Many believe that as time passed and matter cooled, more diverse kinds of atoms began to form, and they eventually condensed into the stars and galaxies of our present universe some 10 billion to 20 billion years ago.
P4: In the steady-state theory, the universe would have existed for ever and would have looked the same at all times, thus adhering to the perfect cosmological principle, a principle that asserts that the observable universe is basically the same at any time as well as at any place. This view is consistent with philosophical approaches that reject the notion of an absolute beginning of the universe as unacceptable. The steady-state universe would have no beginning and no end.
P5: In an expanding universe, as galaxies moved apart, spreading matter more thinly over space, new galaxies would form from matter—in the form of hydrogen— that was supposed to be continually being created throughout space. In addition, the perfect cosmological principle requires that the universe is always expanding but maintaining a constant average density, matter being continuously created to form new stars and galaxies at the same rate that old ones become unobservable with available instruments as a consequence of their increasing distance and velocity of recession. Thus in the steady-state universe, from any point within it the view on the grand scale—the general character and the overall density—is the same. Galaxies of all possible ages are intermingled. Through continuous creation, the steady-state theory is finally compatible with the expanding universe. In this special sense, the steady-state universe itself does not evolve.
P6: Both of the two theories account for the cosmological principle effectively. However, the discovery in the 1960s of comparatively small star-like objects called quasars tipped the scales in favor of Big Bang cosmology. Many astronomers believe that quasars are the most distant objects yet detected in the universe, emitting radio waves and visible light up to 100 times the luminosity of the entire Milky Way Galaxy.
P7: Despite their brightness, due to their great distance from Earth, no quasars can be seen with an unaided eye. Energy from quasars takes billions of years to reach the Earth’s atmosphere. ■ For this reason, the study of quasars can provide astronomers with information about the state of the universe billions of years ago. ■ The fact that almost all quasars are very far away implies that earlier in the history of the universe quasars were developing more frequently than they are now. ■ This evolution is consistent with the Big Bang theory, but it violates the perfect cosmological principle. ■
The word "essential" in the passage is closest in meaning to
选项
A、familiar
B、new
C、fundamental
D、controversial
答案
C
解析
【词汇题】essential意为“基本的”。
转载请注明原文地址:https://kaotiyun.com/show/10fO777K
0
托福(TOEFL)
相关试题推荐
ChooseTWOletters,A-E.WhichTWOpre-existingfeaturesofthesitearenowpartofthenewfacilities?AfootballstadiumBpl
Whenwerethefollowingfeaturesincludedinanautoshow?Writethecorrectletter,A,B,orCnexttoquestions17-20.Alast
Completethenotesbelow.WriteNOMORETHANTWOWORDSforeachanswer.CLIMATEANDARCHITECTURECasesandexamplesarefrompra
A、Therateatwhichtheuniverseisexpanding.B、Howgravityaffectsaplanet’sorbit.C、Newton’sthreelawsofmotion.D、Early
Metaphysicalphilosophy(is)concerned(with)theprinciples,structures,and(meaningful)thatunderlieallobservable(reality
Oneofthebasicprinciplesofwildlifeconservationinvolves______adequatenaturalfoodandsheltertomaintainpopulationso
FamilyMattersThismonth,Wyomingpassedabillthatwouldgivelegalteethtothemoralobligationtosupportone’sparent
FamilyMattersThismonth,Wyomingpassedabillthatwouldgivelegalteethtothemoralobligationtosupportone’sparent
随机试题
刘某于2016年取得某三层小楼的所有权,该一层于2018年转让给了一个储运公司,该储运公司将一楼改为仓库使用,并封死了一、二楼间通行的通道。刘某要求储运公司打通通道,储运公司表示,若要打通通道,需刘某每年支付通行费1万元。对此,下列表述正确的是(
《马伶传》中,马伶两次演《鸣凤记》,他演的人物是________。
颈肿眼突,可诊断为
关于腹膜后淋巴结,不正确的是
A.急性浆液性滑膜炎B.慢性浆液性滑膜炎C.化脓性滑膜炎D.骨关节炎E.关节脱位关节囊高度膨大,无热无痛,触诊有波动感,轻度跛行。该病最可能是
在规划研究咨询的发展战略目标研究中,管理目标包括:体制改革、组织机构、管理制度,以及()等。
关于投资性房地产的后续计量,下列说法中正确的有()。
如图1所示,b是由1分子磷酸、1分子碱基和1分子a构成的化合物。下列叙述正确的是()。
如果Cisco路由器有如下SNMP的配置Router(config)#snmp-serverenabletrapsRouter(config)#snmp-serverhostadmin.tjust.edu.cnadmin
下列关于入侵检测系统探测器获取网络流量的方法中,错误的是()。
最新回复
(
0
)