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
2023-11-13
36
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/3183380.html
相关试题推荐
Annawasreadingapieceofsciencefiction,completely______totheoutsidewo
Notuntilthreeyearsago_____toworkoutside.A、hebeganB、hebeginsC、beganhe
Itis______ofhimtoputeverythingindisorderintheroom.Heissopeculiar
Noonewouldhavetimetoreadorlistentoanaccountofeverything______goin
Cellscannotremainaliveoutsidecertainlimitsoftemperature,andmuchn
Cellscannotremainaliveoutsidecertainlimitsoftemperature,andmuchn
Cellscannotremainaliveoutsidecertainlimitsoftemperature,andmuchn
Cellscannotremainaliveoutsidecertainlimitsoftemperature,andmuchn
Cellscannotremainaliveoutsidecertainlimitsoftemperature,andmuchn
Cellscannotremainaliveoutsidecertainlimitsoftemperature,andmuchn
随机试题
TowardstheendofThinking,FastandSlow,DanielKahnemanlamentsthathe
A.shortenedB.expressionC.originsD.breaks
CanthePCIndustryResurrectItself?A)InternetDataCenter
在骨折的急救中,哪项处理不正确A.首先抢救生命 B.可用当时认为最清洁的布类包
患者,女,36岁,已婚。两次月经中间,阴道少量出血,色鲜红;头晕腰酸,夜寐不宁,
A.握持反射 B.平衡反射 C.吸吮反射 D.吞咽反射 E.提睾反射出生
A. B. C. D.
就房地产开发投资来说,投资回报主要表现形式是()。A:总开发成本B:提取折旧
七年战争
在装饰玻璃中,()玻璃对通过的光线有漫射作用。A.压花 B.刻花 C.冰花
最新回复
(
0
)