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
Virtually everything astronomers known about objects outside the solar system is based on the detection of photons-quanta of ele
Virtually everything astronomers known about objects outside the solar system is based on the detection of photons-quanta of ele
admin
2013-06-03
71
问题
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.
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.
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 wilt 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.
The ocean may be used to detect neutrinos for the following reasons EXCEPT that
选项
A、it can provide massive nucleons.
B、it is like a huge detecting apparatus.
C、it enables neutrinos to move more actively.
D、it can keep away the interference of other particles.
答案
C
解析
推断题。第2段最后两句说明制造中微子探测器的要求,第3段首句提到天体物理学家们想到利用海洋来探测宇宙中微子,由此可推断,海洋应具有第2段末提到的中微子探测器的要求,将四个选项与第2段末对比,即可发现只有选项C没有提及。
转载请注明原文地址:https://kaotiyun.com/show/f3QK777K
0
专业英语四级
相关试题推荐
Everythingintheuniverseundergoes______developmentandchange.
Truepatriotism______puttingtheinterestsofonecountryaboveeverything,______one’slife.
Solidgeometryhasenabledastronomerstocalculatethepositionsoftheheavenlybodies_____tooneanother.
Researchers_____thatgenesmaydeterminethestrengthoftheimmunesystemwhichcouldhelpexplainhowaninfectiousdiseaseco
Although,somestudentsgraduatefromhighschool,theyarevirtuallyilliterate______writingabusinessletter.
Inthesentence"Wefounditimpossibletogeteverythingreadyinsuchshorttime",theitalicizedpartisthe______.
______,heisnotcapableofteachingallsubjects.Afterall,nobodycouldbeanexpertoneverything.
Beliefs,whicharetypicallypartial,oftenwrongandofteninconsistent,butmaynotbedamagingtothesystemasawhole,are
随机试题
研究者若没有向研究对象说明研究的目的和可能带来的不良影响,侵犯了研究对象的哪一项基本权利()
喷雾干燥的特点是
下列()情况中,房地产经纪人可以不回避。
再生水回用过程的监测控制包括()。
对工程造成较大经济损失或延误较短工期,经处理后不影响工程正常使用但对工程寿命有一定影响的事故是()。
如果一方应对方的请求为后者提供了某种服务后,日后对方允诺给予报酬,这项允诺没有拘束力,因为它是过去的对价。()
“脚踏黄河水倒流,搬来泰山做枕头,决心苦战十五年,赶上英国不发愁。”这首新民歌创作的时代背景是“大跃进”时期。()
“文化发展论”和“内化论”是()提出的。
党的十八届三中全会通过了《中共中央关于全面深化改革若干重大问题的决定》,对全面深化改革做出了战略部署,总目标是()
Ifsustainablecompetitiveadvantagedependsonworkforceskills,Americanfirmshaveaproblem.Human-resourcemanagementisno
最新回复
(
0
)