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  3. Virtually everything astronomers known about objects outside the solar syste

Virtually everything astronomers known about objects outside the solar syste

游客2024-01-13  66
问题     Virtually everything astronomers known about objects outside the solar system is based on the detection of photons-quanta of electromagnetic radia- tion. 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 substantialaggregations 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: there- fore, 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 par- ticle 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 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 doubtless bring its own share of surprises. [br] With which of the following statements regarding neutrino astronomy would the author be most likely to agree?
选项 A、Neutrino astronomy will supersede all present forms of astronomy.
B、Neutrino astronomy will be abandoned if the DUMAND project fails.
C、Neutrino astronomy can be expected to lead to major breakthroughs in astronomy.
D、Neutrino astronomy will disclose phenomena that will be more surprising than past discoveries.
E、Neutrino astronomy will always be characterized by a large time lag between hypothesis and experimental confirmation.
答案 C
解析 作者会同意下面关于中微子天文学的哪个观点?A．它将取代所有现存的天文学形式。语气太过。B．如果DUMAND计划失败，中微子天文学也将被放弃。原文可以推出，D计划若成功，中微子天文学将有很大促进。本选项是原文意思的否命题，原命题正确，否命题不一定正确。C．中微子天文学将带来天文学领域大变革。正确。见原文末句。D．中微子天文学将产生比过去更为令人惊异的发现。原文无此比较。E．此门学科总是理论假设和实验差一截。(见原文第二段)过去是这样，但如今有了DUMAND计划，就不再如此了。
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