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
考研
Virtually everything astronomers know about objects outside the solar system is based on the detection of photons-quanta of elec
Virtually everything astronomers know about objects outside the solar system is based on the detection of photons-quanta of elec
admin
2013-06-10
39
问题
Virtually everything astronomers know 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. 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. Not a single, validated observation of an extraterrestrial neutrino has so far been produced despite the construction of a string of elaborate observatories, mounted on the earth from Southern India to Utah to South Africa. However, the detection of extraterrestrial neutrinos are of great significance in the study of astronomy. Neutrinos carry with their information about the site and circum stances 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.
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 sea water 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 doubtlessly bring its own share of surprises.
选项
A、get through,
B、pass by.
C、interact with.
D、derive from.
答案
A
解析
本题问第一段第六行的"escape from"可用什么来代替。首段第四句谈到"Neutrinos can thus escape from regions of space where light...are blocked by matter",由本句中的"thus"可知本句是承接上句内容而说的。而上句谈到"...even traversing substantial aggregations of matter,without being absorbed or even deflected",也就是说中微子可以穿透物质,而不会被吸收,甚至不会偏斜。由此可以推出,第四句中"escape from"也是指从"regions of space"穿过去,丽光等电磁辐射却会被阻隔住(blocked)。故"穿过"正确。实际上中微子可以穿过物质(比如人体),而光子等粒子则会被物质阻挡住,下文中谈到要对探测中微子的设备进行屏蔽,使其不受其他微粒子的影响,正是利用别的微粒子会被物质(比如海水)阻挡住,而中微子则会笔直穿过这一特性。绕过:强干扰项。文意是指中微子可以从物质中穿过(traversing),而不是说遇到物质集团从旁边绕过去。相互作用:这里是指不与物质相互作用,而是从物质中间直接穿过去。源于:文中原意是说中微子能穿越空间,是因为它不受该空间内物质的束缚,而并非是"起源"于该物质。
转载请注明原文地址:https://kaotiyun.com/show/K4d4777K
0
考研英语一
相关试题推荐
Thejokeabout"free-range"chickenisusedinthetexttoTheword"eschew"(paragraph3)isclosestinmeaningto
ReadthefollowingtextcarefullyandthentranslatetheunderlinessegmentsintoChinese.Yourtranslationshouldbewrittencl
Inthefollowingtext,somesentenceshavebeenremoved.ForQuestions41-45,choosethemostsuitableonefromthelist(A、B、C、
Inthefirstparagraph,theauthorismainlyconcernedwith______.Whichofthefollowingistheleastdesirabletoajournali
TheamountofsunlightreachingEarth’ssurfaceappearstobegrowing.Thephenomenon,whichsomedub"globalbrightening",(1)_
Digitalphotographyisstillnewenoughthatmastofushaveyettoformanopinionaboutit,muchless(1)_____apointofview
Manypeopleconsiderthewideruseofbiofuelsapromisingwayofreducingtheamountofsurpluscarbondioxide(CO2n)beingpum
ThechurchofLaPlacita,"thelittlesquare",formallycalledNuestraSeoraReinadeLosAngeles,wasfoundedunderSpanishru
HowClinchWeathertoBecomeWarmProblemTheamountofgreenhousegaseswe’vealreadypumpedintotheatmospherehasirreve
HowClinchWeathertoBecomeWarmProblemTheamountofgreenhousegaseswe’vealreadypumpedintotheatmospherehasirreve
随机试题
近代中国社会的性质和主要矛盾,决定了中国革命的主要敌人是()
行政组织具有________的性质,它既是________实现对社会统治的工具,又是国家政权对社会公共事务进行管理的________。
4岁患儿,3天前突发高热,体温39.5℃,伴寒战,诉右膝部疼痛,给予抗生素治疗后效果不明显,发病后每天只进少量饮食,现患儿膝部皮肤发红发热,肿胀和疼痛越来越严重,膝关节呈半屈曲状,血白细胞计数20.5×109/L,X线检查示膝关节周围软组织肿胀,关节间隙增
使用时可加入适量0.1%枸橼酸钠溶液的是
下列属于《国法大全》的系列的法律汇编有:
案例C企业是建筑施工企业,D公司是化工企业,E公司是D公司的子公司。2015年7月,C企业承接E公司的化工技改项目。2015年8月9日10时,C企业、E公司作业人员在常压容器顶部平台进行氧炔气割作业时,引爆容器内残余可燃气体,导致容器爆炸,平台上
下列()会导致直接人工工资率差异的产生。
李某,30岁,县级中学老师,近期因为一些问题与上级领导发生冲突,受到学校的行政处分,若李某认为学校处分不当,可向()提出申诉。
因为照片的影像是通过光线与胶片的接触形成的,所以每张照片都具有一定的真实性。但是,从不同角度拍摄的照片总是反映了物体某个侧面的真实而不是全部的真实,在这个意义上,照片又是不真实的。因此,在目前的技术条件下,以照片作为证据是不恰当的,特别是在法庭上。以下哪项
CellPhoneLetsYourSecretOutYourcellphoneholdssecretsaboutyou.Besidesthenamesand【51】thatyou’veprogrammedin
最新回复
(
0
)