首页
登录
职称英语
Virtually everything astronomers known about objects outside the solar syste
Virtually everything astronomers known about objects outside the solar syste
游客
2024-01-13
43
管理
问题
Virtually everything astronomers known about objects outside the solar system is based on the detection of photons-quanta of electromagnetic radia- tion. Yet there is another form of radiation that permeates the universe: neutrinos. 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 substantialaggregations 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: there- fore, the detection of cosmic neutrinos could provide new information about a wide variety of cosmic phenomena and about the history of the universe.
But how can scientists detect a par- ticle 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.
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.
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, and pulsars. Each of these discoveries came as a surprise. Neutrino astronomy will doubtless bring its own share of surprises. [br] Which of the following titles best summarizes the passage as a whole?
选项
A、At the Threshold of Neutrino Astronomy
B、Neutrinos and the History of the Universe
C、The Creation and Study of Neutrinos
D、The DUMAND System and How It Works
E、The Properties of the Neutrino
答案
A
解析
哪一个是描述文章内容的合适选项?(此题是主题题型的变种)A.正确。中微子天文学的开端。文章一开始就指出天体观测中中微子是一个重要工具,最后又指出对中微子的观测的原因就是它可能提供有关宇宙的重要的信息。因此,一切对中微子的考察、研究都是为天文学这一目标服务。B.中微子和宇宙历史。不够准确。C.中微子制造和研究。这是中间一大段内容,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作出贡献。D.DUMAND方式。只是文中部分内容。E.中微子性质。只是文中部分内容。
转载请注明原文地址:https://tihaiku.com/zcyy/3359267.html
相关试题推荐
Whathesaidwasquite______,therefore,Iwoulddoeverythingtohelphim.A、val
______,everythingwouldhavebeenallright.A、HehadbeenthereB、Herehehadb
Don’tworryifyoucan’tunderstandeverything.Theteacherwill______themain
JardenZincProducts,alargezincplantafewmilesoutsideGreeneville,Ten
JardenZincProducts,alargezincplantafewmilesoutsideGreeneville,Ten
Bytheendofnextmonthhe______everythinginschool.A、willfinishB、wouldhave
JardenZincProducts,alargezincplantafewmilesoutsideGreeneville,
JardenZincProducts,alargezincplantafewmilesoutsideGreeneville,
Bytheendofnextmonthhe___________everythinginschool.A、willfinishB、would
WhenIwasalittlegirl,Iwasinterestedineverythingaroundme.Whenmy
随机试题
[originaltext]AnenvironmentalgroupcalledtheFoodCommissionisunhappy
社会知觉就是对人的知觉,就是对人和社会群体的知觉,就是对()的知觉。A.工作对
下列降低血糖的激素是A.胰岛素 B.胰高血糖素 C.糖皮质激素 D.生长激
评估风险管理效果是指对风险管理策略的()及收益性情况的分析、检查、修正和
证券产品进场时机选择的要求( )。 Ⅰ.选择进场时机需要积极的投资思维跟进
患者,男,38岁。两手出现皮下小水疱,疱壁破裂,叠起白皮,中心已愈,四周续起疱疹
小青龙汤中不包括的药物是A细辛、干姜 B桂枝、甘草 C半夏、五昧子 D苦杏
企业将活动项目、品牌和产品等信息以网络新闻通稿的方式在门户网站以及行业网站等平台
根据证券法律制度的规定,下列关于非公开发行公司债券的表述中,正确的是()。
早期胃癌是指( )。A.侵及黏膜下层及肌层的癌 B.直径小于2cm的癌 C
最新回复
(
0
)