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
(l)Virtually everything astronomers known about objects outside the solar system is based on the detection of photons-quanta of
(l)Virtually everything astronomers known about objects outside the solar system is based on the detection of photons-quanta of
admin
2017-02-18
84
问题
(l)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 (中徽子). 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.
In the last paragraph, the author describes the development of astronomy in order to ______.
选项
A、suggest the potential discovery of celestial bodies by means of neutrino astronomy
B、illustrate the importance of surprises in making astronomic discoveries
C、demonstrate the effectiveness of the DUMAND apparatus in detecting neutrinos
D、name some cosmic phenomena that neutrino astronomy will illuminate
答案
A
解析
推断题。末段末句中的its own share of surprises及该句时态表明中微子天文学也将像该段第2句提到的天文学发展那样为天体的发现做出贡献,因此本题答案应为选项A。
转载请注明原文地址:https://kaotiyun.com/show/SvJK777K
0
专业英语四级
相关试题推荐
Whichofthefollowingcontainsanadverbialclauseofcause?
WhichofthefollowingitalicizedphrasesisINCORRECT?
Susandoesn’twanttoworkrightawaybecauseshethinksthatifshe______ajob,sheprobablywouldn’tbeabletoseeherfrie
Muchas______,Icouldn’taccompanyhimtotheconcertbecauseIsimplydidn’thaveanysparetime.
Theshopassistantguaranteedthattheantiqueis______,notaverygoodfake.
You______businessaskinghimtodosuchathing.
Itisbelievedthataperson’ssocialskillscontributealottohissuccess.Someuniversitystudentswhocannotlandajobaft
Healthis______countsmost.
WetsuitAwetsuitis【T1】______whowantto【T2】______.Wetsuitsareusuallywornbyswimmers,divers,or【T3】______.Wetsuitsh
In"Thelittlegirlisleftaloneinthehouse,weepingbitterly"theunderlinedpartisthe______ofthesentence.
随机试题
范××,男,18岁,因突发左侧胸痛、胸闷1天入院。疼痛在打篮球时发生,呈撕裂样,深呼吸后加剧,疼痛为一过性,无发热、咳嗽等,无外伤史,既往无心脏病史。体格检查:T37℃,P80次/分,R20次/分,Bp100/70mmHg,气管右移。左胸饱满,呼吸
关于软膏剂的表述,不正确的是()
抑郁症的急性期,抗抑郁剂治疗至少
根据《建筑工程建筑面积计算规范》,有永久性顶盖无围护结构的按其结构底板水平1/2面积计算建筑面积的是()
设备基础验收时,提供的移交资料包括()。
排水管道圆形检查井的砌筑做法不包括()。
某大学团队研究了“干细胞间竞争”在小鼠尾部皮肤老化中的作用。结果表明,“干细胞间竞争”由胶原蛋白COL17A1驱动。他们发现,COL17A1的表达在不同干细胞间存在差异,COL17A1表达水平较高的干细胞会牢固地锚定于基底膜,且对称分裂,并将附近COL17
“商品”与“顾客”两个实体集之间的联系一般是
十进制整数100转换为二进制数是
InhisplaysShakespeare______hischaracterslivethroughtheirlanguage.
最新回复
(
0
)