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 that
From the beginning, the idea of a finite universe ran into its own obstacle, the apparent need for an edge, a problem that
admin
2009-05-19
56
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
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.
选项
A、searching for an accurate method of determining whether the universe is finite or infinite
B、discussing problems and possibilities involved in providing a definite picture of the shape of the universe
C、declaring opposition to the notion that spherical geometry is a possible model for the shape of the universe
D、criticizing discredited theories about the possible topologies of the universe
E、refuting the idea that there is no way to tell whether the universe is finite and if so what shape it has
答案
B
解析
转载请注明原文地址:https://kaotiyun.com/show/JOkO777K
本试题收录于:
GRE VERBAL题库GRE分类
0
GRE VERBAL
GRE
相关试题推荐
Accordingtothepassage,nonverbalcommunication______.Constantsmilingwithoutapparentreason______.
______,Ihavetoputitawayandfocusmyattentiononstudythisweek.
Accordingtoarecenttheory,Archean-agegold-quartzveinsystemswereformedovertwobillionyearsagofrommagmaticfluidst
Justasplantspeciesnativetoregionswithbrowsingmammalsevolvedmanynaturalanti-browserdefenses(suchassharpspinesan
Thehumangrowthhormone,madebythepituitarygland,issecretedduringsleepinhigherconcentrationsthanwhenawake.
Whichofthefollowingisclosesttotheaverage(arithmeticmean)numberofcardinalsightingsforthe4seasons?
QUANDARY:
Certainmuseumantiquitiesareofquestionablelegalstatus,taintedbyhistoriesofbribery,thievery,andother______activitie
Despiteclaimsthathisphilosophycanbetracedto(i)____source,thephilosophyinfactdrawsliberallyonseveraltraditions
Nooneis(i)____aboutStephens;heinspireseitheruncriticaladulationorprofound(ii)____inthosewhoworkforhim.
随机试题
【背景资料】某机电安装公司通过竞标承担了某工厂的设备、管道安装工程。为兑现投标承诺,该公司通过质量策划,编制了施工组织设计和相应的施工方案,并建立了现场质量保证体系,制定了检验试验卡,要求严格执行三检制。工程进入后期,为赶工期,采用加班加点的办法加快管道
物联网必须能支持现有______中的基本协议。
能治疗食积脘腹胀痛的药物是()
商业银行不得将同业拆入资金用于()。
善意取得是指无权处分他人财物的占有人,将财物转让给第三人以后,如果受让人在取得该动产时出于善意(非基于故意和重大过失,而对转让人无处分权的情形不知情),就可以依法取得对该动产的所有权,受让人在取得动产的所有权以后,原所有人不得要求受让人返还财产,而只能请求
下面是某求助者的EPQ测验结果:该求助者的量表得分说明其()。
计算:sin230°+tan44°.tan46°+sin260°=________.
王红守在天文望远镜前足足盯了两个小时,要观察的小行星终于出现在视野里。这反映了注意的()
门德尔松的《_________序曲》被认为是第一部真正的音乐会序曲。
A、Adeterminerthatleadspeopletobringtheproductintotheirlives.B、Acompleteliethatleadspeopletobuytheproduct.C
最新回复
(
0
)