首页
登录
职称英语
(1)Virtually everything astronomers known about objects outside the solar sy
(1)Virtually everything astronomers known about objects outside the solar sy
游客
2024-09-01
2
管理
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. [br] 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://tihaiku.com/zcyy/3738307.html
相关试题推荐
Wecanuseoureyesandfacialexpressionstocommunicatevirtuallyevery______n
Tomisimmenselycuriousabouteverythingandaseagertofindtheanswersasif
Thefloor________wetandslippery,westayedoutside.A、tobeB、beenC、beingD、
Theirwithdrawalfromtheworldeconomyisvirtuallyimpossible.Theunderlined
Asyoutouchpeople,surfacesandobjectsthroughouttheday,you________germs
A.hardlyB.chemistryC.virtuallyD.counterparts
A.hardlyB.chemistryC.virtuallyD.counterparts
A.hardlyB.chemistryC.virtuallyD.counterparts
A.hardlyB.chemistryC.virtuallyD.counterparts
A.hardlyB.chemistryC.virtuallyD.counterparts
随机试题
挡土墙设计应重视墙后排水,所以墙后填土应尽量选用()oA.砂土 B.耕植土
天王补心丹与朱砂安神丸组成中均含有的药物有( )。A.酸枣仁 B.炙甘草
Thefunctionofthesentence“Australiali
下列关于量化投资分析的说法中,正确的有()。 Ⅰ.严格执行量化投资模型所
共用题干 MemoryTest1"Iamgoingtogivey
患者,男性,27岁,酒后4h剧烈腹痛。患者中午聚餐,饮6两白酒。下午出现剧烈、持
“行政机关实施行政管理,应当依照法律、法规、规章的规定进行;没有法律、法规、规章
基金经理的任职资格条件之一是具有2年以上证券投资管理经历。()
投资项目决策分析与评价的基本要求包括贯彻落实科学发展观、资料数据准确可靠和()
个体特征包括年龄、性别、持续劳动能力、负重能力、运动速度、感觉敏锐度等,它与劳动
最新回复
(
0
)