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  3. Black holes are one of only a fairly small number of cases in the history of science in which a theory was developed in great de

Black holes are one of only a fairly small number of cases in the history of science in which a theory was developed in great de

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问题    Black holes are one of only a fairly small number of cases in the history of science in which a theory was developed in great detail as a mathematical model before there was any evidence from observations that it was correct. 【F1】Indeed, this used to be the main argument of opponents of black holes: how could one believe in objects for which the only evidence was calculations based on the dubious theory of general relativity? In 1963, however, Maarten Schmidt, an astronomer at the Palomar Observatory in California, measured the red shift of a faint starlike object in the direction of the source of radio waves called 3C273. He found it too large to be caused by a gravitational field: if it had been a gravitational red shift, the object would have to be so massive and so near to us that it would disturb the orbits of planets in the Solar System. 【F2】This suggested that the red shift was instead caused by the expansion of the universe, which, in turn, meant that the object was a very long distance away. And to be visible at such a great distance, the object must be very bright, must, in other words, be emitting a huge amount of energy. 【F3】The only mechanism that people could think of that would produce such large quantities of energy seemed to be the gravitational collapse not just of a star but of a whole central region of a galaxy.
   Further encouragement for the existence of black holes came in 1967 with the discovery by a research student at Cambridge, Jocelyn Bell-Burnell, of objects in the sky that were emitting regular pulses of radio waves. At the seminar at which Bell and her supervisor announced their discovery, I remember that they called the first four sources to be found LGM 1-4, LGM standing for "Little Green Men." In the end, however, they and everyone else came to the less romantic conclusion that these objects were in fact rotating neutron stars (中子星) that were emitting pulses of radio waves because of a complicated interaction between their magnetic fields and surrounding matter. 【F4】This was bad news for writers of space westerns, but very hopeful for the small number of us who believed in black holes at that time: it was the first positive evidence that neutron stars existed. A neutron star has a radius of about ten miles, only a few times the critical radius at which a star becomes a black hole. 【F5】If a star could collapse to such a small size, it is not unreasonable to expect that other stars could collapse to even smaller size and become black holes.
【F3】
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答案人类目前能想到的、可产生如此巨大能量的方式似乎只有重力崩溃，不仅仅是恒星的重力崩溃，甚至还是整个银河系中心区域的重力崩溃。
解析 ①本句是较复杂的复合句，句子的主干为主系表结构(The only mechanism seemed to be the gravitational collapse．．．)。②主语The only mechanism后接两个定语从句，一起修饰mechanism，说明其两个特点，分别是“人类能想到的”和“可产生巨大能量的”。定语从句1是由that引导的，that既是引导词也充当从句的宾语；定语从句2同样是由that作引导词，但引导词在从句中充当主语。③主干的表语the gravitational collapse后被两个并列的of介词短语所修饰(of a star和of a whole central region of a galaxy)，由not just．．．but．．．连接，说明重力坍塌的两处地方。
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