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
2024-10-12
31
管理
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. [br] One advantage that neutrinos have for studies in astronomy is that they
选项
A、have been detected for 25 years.
B、possess a variable electric charge.
C、are usually extremely massive.
D、record information about their own origin.
答案
D
解析
细节题。选项D是对首段末句中的第一个原因分句的近义改写,因此选项D为本题答案。
转载请注明原文地址:https://tihaiku.com/zcyy/3797944.html
相关试题推荐
AstronomersattheUniversityofCaliforniadiscoveredoneofthemostdistant_
TheDiscoveryofAstronomersThediscoveryofplanetsar
TheDiscoveryofAstronomersThediscoveryofplanetsar
TheDiscoveryofAstronomersThediscoveryofplanetsar
Itwassurprisingthatthehotellookedrathershabbyoutsidewasluxuriouslyan
Whatkindofweatherwillitbewhendistantobjectssuchashillsandtalltree
Whatkindofweatherwillitbewhendistantobjectssuchashillsandtalltree
Whatkindofweatherwillitbewhendistantobjectssuchashillsandtalltree
Everythingisready,______?A、isn’titB、aren’ttheyC、isitD、aretheyA此题考查反意疑
Theenvironmentiseverythingthatsurroundsus:plants,animals,buildings
随机试题
Sincetheenergycrisis,thesebigcarshavebecomearealliability.Theycost
IsCollegeReallyWorththeMoney?TheReal
语句中没有通假字的是()A.少益嗜食 B.庄公寤生 C.勿使反 D.花林
Berg平衡量表评定中从坐位站起3分提示A.不用手扶即能独立站起并保持稳定 B
妊娠期妇女治疗口腔疾病的适宜时期是A.妊娠初期(1~3个月) B.妊娠中期(4
A.上或中输尿管点压痛 B.肋脊点、肋腰点压痛及叩击痛 C.肾脏缩小 D.
A.风池 B.肩髃 C.大椎 D.天宗 E.至阳落枕兼背痛者,宜配用(
K线图中,当()低于开盘价时,形成阴线。A.结算价 B.收盘价 C.
房地产开发项目工程设计的基本原则有()。A:合理利用资源 B:尽量压缩成本
化脓性脑膜炎A、糖正常,氯化物升高,蛋白明显下降,细胞数升高,以中性粒细胞为主
最新回复
(
0
)