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
From the beginning, the idea of a finite universe ran into its own obstacle, the apparent need for an edge, a problem tha
From the beginning, the idea of a finite universe ran into its own obstacle, the apparent need for an edge, a problem tha
admin
2011-01-17
41
问题
From the beginning, the idea of a finite universe ran into its own obstacle,
the apparent need for an edge, a problem that has only recently been grappled
with. Aristotle’s argument, that the universe is finite, and that a boundary was
Line necessary to fix an absolute reference frame, held only until scientists wondered
(5) what happened at the far side of the edge. In other words, why do we not
redefine the "universe" to include that other side?
Riemann ingeniously replied by proposing the hypersphere, the three-
dimensional surface of a four-dimensional ball. Previously it was supposed that
the ultimate physical reality must be a Euclidean space of some dimension, and
(10) thus if space were a hypersphere, it would need to sit in a four-dimensional
Euclidean space that allows us to view it from the outside. But according to
Riemann, it would be perfectly acceptable for the universe to be a hypersphere
and not embedded in any higher-dimensional space; nature need not therefore
cling to the ancient notion. According to Einstein’s powerful but limited theory
(15) of relativity, space is a dynamic medium that can curve in one of three ways,
depending on the distribution of matter and energy within it, but because we are
embedded in space, we cannot see the flexure directly but rather perceive it as
gravitational attraction and geometric distortion of images. Thus, to determine
which of the three geometries our universe has, astronomers are forced to
(20) measure the density of matter and energy in the cosmos, whose amounts appear
at present to be insufficient to force space to arch back on itself in "spherical"
geometry. Space may also have the familiar Euclidean geometry, like that of a
plane, or a "hyperbolic" geometry, like that of a saddle. Furthermore, the
universe could be spherical, yet so large that the observable part seems
(25) Euclidean, just as a small patch of the earth’s surface looks flat.
We must recall that relativity is a purely local theory: it predicts the
curvature of each small volume of space-its geometry-based on the matter
and energy it contains, and the three plausible cosmic geometries are consistent
with many different topologies: relativity would describe both a torus and a
(30) plane with the same equations, even though the torus is finite and the plane is
infinite. Determining the topology therefore requires some physical
understanding beyond relativity, in order to answer the question, for instance,
of whether the universe is, like a plane, "simply connected", meaning there is
only one direct path for light to travel from a source to an observer. A simply
(35) connected Euclidean or hyperbolic universe would indeed be infinite-and seems
self-evident to the layman-but unfortunately the universe might instead be
"multiply-connected", like a torus, in which case there are many different such
paths. An observer could see multiple images of each galaxy and easily interpret
them as distinct galaxies in an endless space, much as a visitor to a mirrored
(40) room has the illusion of seeing a huge crowd, and for this reason physicists have
yet to conclusively determine the shape of the universe.
Which of the following does the passage imply about the notion that the universe may be based on a spherical geometry?
选项
A、Of the three models of spatial curvature proposed by Einstein, only spherical geometry contradicts the Euclidean model.
B、The primary evidence for the notion is that that observers cannot see spatial flexure directly, but perceive it as gravitational attraction.
C、Space mapped on the spherical geometrical model may curve in one of three ways, as Einstein proposed.
D、Spheres typically contain only three dimensions, whereas most models of the universe attribute it at least four.
E、Scientists are skeptical, given that mass and energy quantities seem insufficient, yet ultimately do not know enough to dismiss the notion.
答案
E
解析
转载请注明原文地址:https://kaotiyun.com/show/nFjO777K
本试题收录于:
GRE VERBAL题库GRE分类
0
GRE VERBAL
GRE
相关试题推荐
Ifyoudon’tputthemilkintherefrigerator,itmay______.
Cancellationoftheflight______manypassengerstospendthenightattheairport.
Thefamousnovelissaid______intoChinese.
Anystudentwho______hishomeworkisunlikelytopasstheexamination.
TheclimateinLondonisquitepleasant,thetemperaturerarely,ifany,______30℃.
Seldomdidwerealizethatmanyofourhairproblems______whatweeat.
Thestudentsdidn’tmanagetoworkouttheproblem______theirteacherhadexplainedhow.
SpeakerA:Hello,Iwanttobuysomeclothesformygirlfriendforherbirthdaypresent.SpeakerB:Noproblem,sir.【D8】_____
AlthoughthephenomenonofwithdrawalhasalwaysbeenthecrucialphysiologicalLengfordistinguishingaddictivefromnon-addic
Despiteits(i)______,thebookdeals(ii)______withanumberofcrucialissues.
随机试题
某单位财务处请小张设计《经费联审结算单》模板,以提高日常报账和结算单审核效率。请根据考生文件夹下“Word素材1.docx”和“Word素材2.xlsx”文件完成制作任务,具体要求如下:设置《××研究所科研经费报账须知》的第一行格式为小三、黑体、加粗,
机动车在高速公路上行车,如果因疏忽驶过出口,可沿路肩倒车退回出口处。
作为国际政治基本行为主体的主权国家必须具备的基本要素有______、______、______、______。
对防止骨粘合剂反应的发生有利的措施为
依据《固体废物污染环境防治法》,()固体废物的单位和个人,必须采取防扬散、防流失、防渗漏或者其他防止污染环境的措施。
根据《水利水电建设工程验收规程》SL223—2008的有关要求,“竣工验收鉴定书”中对工程建设施工单位的叙述到()。
省政府关于第七届××省农业技术推广奖的决定×政发[2015]17号各市、县(市、区)人民政府,省各委办厅局,省各直属单位:近年来,全省各地、各有关部门大力推进
()一般没有固定的回报要求。
"Civilization"Between4000and3000B.C.,significanttechnologicaldevelopmentsbegantotransformtheNeolithictowns.The
RupertBrookeRupertBrooke,oneoftheleadingpoetsofhisgeneration,wasrenownedasaromantic,unlikemanyofhiscon
最新回复
(
0
)