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  3. Any physical theory is always provisional, in the sense that it is only a hypothesis: you can never prove it. No matter how many

Any physical theory is always provisional, in the sense that it is only a hypothesis: you can never prove it. No matter how many

admin2011-01-02  77
问题    Any physical theory is always provisional, in the sense that it is only a hypothesis: you can never prove it. No matter how many times the results of experiments agree with some theory, you can never be sure that the next time the result will not contradict the theory. On the other hand, you can disprove a theory by finding even a single observation that disagrees with the predictions of the theory. As philosopher of science, Karl Popper has emphasized a good theory is characterized by the fact that it makes a number of predictions that could in principle be disproved or falsified by observation. Each time new experiments are observed to agree with the predictions the theory survives, and our confidence in it is increased; but if ever a new observation is found to disagree, we have to abandon or modify the theory. At least that is what is supposed to happen, but you can always question the competence of the person who carried out the observation.
   In practice, what often happens is that a new theory is devised that is really an extension of the previous theory. For example, very accurate observations of the planet Mercury revealed a small difference between its motion and the predictions of Newton’s theory of gravity. Einstein’s general theory of relativity predicted a slightly different motion from Newton’s theory. The fact that Einstein’s predictions matched what was seen, while Newton’s did not, was one of the crucial confirmations of the new theory. However, we still use Newton’s theory for all practical purposes because the difference between its predictions and those of general relativity is very small in the situations that we normally deal with. (Newton’s theory also. has the great advantage that it is much simpler to work with than Einstein’s ! )
    It turns out to be very difficult to devise a theory to describe the universe all in one go. Instead, we break the problem up into bits and invent a number of partial theories. Each of these partial  theories describes and  predicts a certain limited class of observations, neglecting the effects of other quantities, or representing them by simple sets of numbers. It may be that this approach is completely wrong. If everything in the universe depends on everything else in a fundamental way, it might be impossible to get close to a full solution by investigating parts of the problem in isolation. Nevertheless, it is certainly the way that we have made progress in the past. The classic example again is the Newtonian theory of gravity, which tells us that the gravitational force between two bodies depends only on one number associated with each body, its mass, but is otherwise independent of what the bodies are made of.  Thus one does not need to have a theory of the structure and constitution of the sun and the planets in order to calculate their orbits:
   Today scientists describe the universe in terms of two basic partial theories-the general theory of relativity and quantum mechanics. They are the great intellectual achievements of the first half of this century. Unfortunately, however, these two theories are known to be inconsistent with each other-they cannot both be correct. One of the major endeavours in physics today, is the search for a new theory that will incorporate them both-a quantum theory of gravity. We do not yet have such a theory, and we may still be long way from having one, but we do already know many of the properties that it must have.
According to the last paragraph, the author may suggest that______.
选项 A、either of the two partial theories may be correct
B、the new theory has been established to replace the two partial theories
C、the new theory may develop from either of the two partial theories
D、the new theory may combine many of the properties of the two partial theories
答案D
解析 最后一段谈到两个基本的“不完全理论”——相对论和量子机械论，二者是互不相容的，即这两个理论不可能同时成立。物理学如今要做的是寻找一种能兼容这两个理论的新理论。D最符合原文的意思。
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