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
(1)Virtually everything astronomers known about objects outside the solar system is based on the detection of photons-quanta of
(1)Virtually everything astronomers known about objects outside the solar system is based on the detection of photons-quanta of
admin
2021-08-31
45
问题
(1)Virtually everything astronomers known about objects outside the solar system is based on the detection of photons-quanta of electromagnetic radiation. Yet there is another form of radiation that permeates the universe: neutrinos (中微子). With (as its name implies) no electric charge, and negligible mass, the neutrino interacts with other particles so rarely that a neutrino can cross the entire universe, even traversing substantial aggregations of matter, without being absorbed or even deflected. Neutrinos can thus escape from regions of space where light and other kinds of electromagnetic radiation are blocked by matter. Furthermore, neutrinos carry with them information about the site and circumstances of their production: therefore, the detection of cosmic neutrinos could provide new information about a wide variety of cosmic phenomena and about the history of the universe.
(2)But how can scientists detect a particle that interacts so infrequently with other matter? Twenty-five years passed between Pauli’s hypothesis that the neutrino existed and its actual detection: since then virtually all research with neutrinos has been with neutrinos created artificially in large particle accelerators and studied under neutrino microscopes. But a neutrino telescope, capable of detecting cosmic neutrinos, is difficult to construct. No apparatus can detect neutrinos unless it is extremely massive, because great mass is synonymous with huge numbers of nucleons (neutrons and protons), and the more massive the detector, the greater the probability of one of its nucleon’s reacting with a neutrino. In addition, the apparatus must be sufficiently shielded from the interfering effects of other particles.
(3)Fortunately, a group of astrophysicists has proposed a means of detecting cosmic neutrinos by harnessing the mass of the ocean. Named DUMAND, for Deep Underwater Muon and Neutrino Detector, the project calls for placing an array of light sensors at a depth of five kilometers under the ocean surface. The detecting medium is the seawater itself: when a neutrino interacts with a particle in an atom of seawater, the result is a cascade of electrically charged particles and a flash of light that can be detected by the sensors. The five kilometers of seawater above the sensors will shield them from the interfering effects of other, high-energy particles raining down through the atmosphere.
(4)The strongest motivation for the DUMAND project is that it will exploit an important source of information about the universe. The extension of astronomy from visible light to radio waves to x-rays and gamma rays never failed to lead to the discovery of unusual objects such as radio galaxies, quasars (类星体), and pulsars (脉冲星). Each of these discoveries came as a surprise. Neutrino astronomy will doubtless bring its own share of surprises.
Which might be the most appropriate title of the passage?
选项
A、At the Threshold of Neutrino Astronomy.
B、Neutrinos and the History of the Universe.
C、The Creation and the Study of Neutrinos.
D、The DUMAND System and How It Works.
答案
A
解析
主旨题。文章一开始就指出天体观测中中微子是一个重要粒子,最后又指出观测中微子的原因是它可能提供重要的有关宇宙的信息,因此,一切对中微子的考察和研究都是为天文学这一目标服务,只有选项A概括了中微于和天文学这两个重点。原文并没有介绍宇宙历史。因此选项B不准确;选项C是原文第1、2段涉及的内容,但本文作者不是以研究中微子为最终目的,研究它是为了对天文学做出贡献。选项D只是最后两段提到的内容,不是文章主旨。
转载请注明原文地址:https://kaotiyun.com/show/573K777K
0
专业英语四级
相关试题推荐
Whichofthefollowingitalicizedpartsisasubjectclause?
A.causeB.chainC.componentD.criticalE.growingF.increaseG.inherentlyH.linkI.mutually
Whichofthefollowingsentencescontainsasubjectclause?
PASSAGETWOWhydidtheshopassistantleadtheelderlywomantofindtheDVDinsteadoffindingitforher?
MakeYourHolidaysMoreMeaningfulBeforetheholidayseason-【T1】______aweeklycalendar【T1】______-starteliminat
ItishardtoimaginelifewithoutdigitalsearchandtheInternet./Thisisastrueformeasforanyoneelse./Thegreatere
IsraelandHamashadreachedadealonextendingthe______ceasefirebyanextra24hoursuntilTuesdayatmidnight.(2016-27)
[A]growing[B]trade[C]host[D]rarely[E]faster[F]tourism[G]claiming[H]slower[I]police[J]usually[K]crimes[L]sound[M]giving[N]peopl
[A]befriend[B]directly[C]drives[D]slide[E]various[F]enormous[G]dumb[H]produce[I]blindly[J]affection[K]aware[L]observe[
A、Increasingsignageattheintersections.B、Bearingthepowerlinesunderground.C、Keepingcarsawayfromthearea.D、Erecting
随机试题
通过门静脉系统进入肝脏,造成肝脏病变的寄生虫有
下列哪些属于肾性骨营养不良症
我国母婴保健法的立法宗旨是
膀胱炎最易发生于
甲有两子,长子乙,次子丙,丙有残疾,无自立生活能力。2012年乙为甲投保了人寿保险,期限10年,受益人为丙。后甲因病住院,在甲住院时,乙未经甲同意,将保险单交给邻居丁作质押,借款一万元。甲因病医治无效,四个月后去世。丁催乙还款,乙不还。保险公司通知丙领取保
针对以上情况,在估价时最恰当的做法是()。委托人要求估价机构按照委托人的估价目的对甲、乙两个厂区的房屋和土地进行估价。估价机构认为()。
家长会上,班主任张老师对待优等生的家长犹如春风,对待后进生家长的态度却冷若冰霜。张老师的做法()。
学校及其他教育机构在不影响教育活动的前提下,应该积极参与当地社会公益活动。()
设随机变量X和Y相互独立,且分布函数为FX(x)=令U=X+Y,则U的分布函数为________.
运营部经理老钱需要对公司本年度的购销数据进行统计,请按照下列要求帮助老钱完成相关数据的整理、计算和分析工作:在工作表“年度销售汇总”右侧插入一个名为“品名”的工作表,按照下列要求对其进行整理完善:①将以逗号“,”分隔的文本文件“品名表.txt
最新回复
(
0
)