新发展大学英语阅读与写作3课文翻译What Is a Scientific Theory 什么是科学理论

What Is a Scientific Theory?

In order to talk the mature of the universe and to discuss questions such as whether it has a beginning or an end, you have to be clear about what a scientific theory is. I shall take the simple-minded view that a a theory is just a model of the universe, of a restricted part of it, and a set of rules that relate quantities in the model to observations that we make, It exists only in our minds an does not have any other reality (whatever that night mean). A theory is a good theory if it satisfies two requirements: It must accurately describe a large class of observations on the basis of a model that contains only a few arbitrary elements, and it must make definite predictions about the results of future observations. For exampl e, Aristotle’s theory that everything was made out of four elements, earth, air, fire, and water, was simple enough to qualify, but it did not make any definite predictions. On the other hand, Newton’s theory was proportional to a quantity called their mass and inversely proportional to the square of the distance between them. Yet it predicts the motions of the sun, the moon, and the planets to a high degree of accuracy.

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!)

The eventual goal of science is to provide a single theory that describes the whole universe. However, the approach most scientists actually follow is to separate the problem into two parts. First, there are the laws that tell us how the universe changes with time. (If we know what the universe is like at any one time, these physical laws tell us how it will look at any later time.) Second, there is the question of the initial state of the universe. Some people feel that science should be concerned with only the first part; they regard the question of the initial situation as a matter for meta-physics of religion. They would say that God, being omnipotent, could have made it develop in a company way he wanted. That may be so, but in that case he also could have made it develop in a completely arbitrary way. Yet it appears that he chose to make it evolve in a very regular way according to certain laws. It therefore seems equally reasonable to suppose that there are also laws governing the initial state.

It turns out to be very difficult to device 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 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. The general theory of relativity describes the force of gravity and the large-scale structure of the universe, that is , the structure on scales from only a few miles to as large as a million million million (1 with zeros after it) miles, the size of the observable universe. Quantum mechanics, on the other hand, deals with phenomena ion extremely small scales, such as a millionth of a millionth of an inch. Unfortunately, however, these two theories are known to be inconsistent with each other – they cannot both be correct. One of the major endeavors in physics today, is the search for a new theory, and we may still be a long way from having one, but we do already know many of the properties that it must have.

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什么是科学理论?

为了谈宇宙的成熟和讨论这样的问题是否有一个开始或结束,你必须清楚科学理论是什么。我将以头脑简单的观点,一个一个的理论只是一个宇宙模型,一个受限制的一部分,和一组规则,涉及数量的模型来观测,我们制作的,它只存在于我们的头脑一个没有任何其他现实(无论那夜的意思)。一个理论是一个很好的理论如果它满足两个条件:它必须准确地描述一个大班级的观测模型的基础上,只包含几个任意元素,它必须明确预言未来的观测结果。例如,亚里士多德的理论,一切都是由四种元素、土、空气、火和水,很简单,但它够资格未作任何明确的预测。另一方面,牛顿的理论是成比例的量称为他们的质量和成反比的平方与它们之间的距离。但它预言的动作,太阳、月亮和行星以一种高度精确的方式。

任何物理理论始终是临时的,在某种意义上,它只是一个假说:你永远无法证明这一点。无论多少次实验的结果,同意一些理论,不能保证下次结果不会反驳这个理论。另一方面,你可以证明一个理论通过发现甚至单个观察,不同意的预测理论。作为科学哲学家卡尔·波普尔强调,一个良好的理论的特点是事实,它使一个数量的预测,可以证明或证伪原则是通过观察。每一次新的实验观察到同意预测理论活了下来,而我们的信心增加,

但是如果有一个新的观察是发现不同意,我们不得不放弃或修改理论。至少这是应该发生的,但是你总是可以质疑能力的人进行了观察。

在实践中,经常发生的是,一个新的理论设计了,真是一个扩展先前的理论。例如,非常准确的观测水星,发现一个小的差异的预测其运动和牛顿的引力理论。爱因斯坦的广义相对论预言一个稍微不同的运动从牛顿的理论。事实上,爱因斯坦的预测匹配所看到的,而牛顿没有之一了新的理论的正确性。然而,我们仍然使用牛顿的理论实际上因为其预测之间的区别和广义相对论是非常小的情况下,我们通常处理。(牛顿的理论也有

很大的优势,它是非常简单的处理比爱因斯坦的!)

科学的最终目标是提供一个单一的理论,描述了整个宇宙。然而,这种方法实际上遵循大多数科学家是单独的问题分为两部分。首先,有法律,告诉我们宇宙是如何随时间变化。(如果我们知道宇宙像在任何一个时间,这些物理定律告诉我们它将如何在以后的时间里看。)第二,有问题的初始状态的宇宙。一些人认为科学应该关心只有第一部分;他们认为问题的初始情况作为重要的宗教为元物理学。他们会说,上帝,无所不能,可以使它在一个公司发展他想要的。那也许是这样,但在这种情况下他还能使它发展在一个完全任意的方式。但看来他选择让它发展在一个非常普通的方式按照一定的规律。因此似乎同样合理的假设也有法律规定初始状态。

事实证明很难装置一个理论来描述宇宙的所有在一个去。相反,我们把问题分成碎片和发明一些偏理论。其中每个部分的理论描述和预测某种有限的课堂的观察,忽略了其他的物理量的影响,或代表他们通过简单的套数字。它可能是,这种方法是完全错误的。如果宇宙中的一切都取决于其他所有在一个基本方式,它可能是不可能接近一个完整的解决方案,调查过去的一部分。典型的例子再次是牛顿的引力理论,它告诉我们,两个物体之间产生的引力只取决于一个号码与相关各体,它的质量,但是另有独立的机构是由。因此不需要结构的理论和宪法的太阳和行星为了计算它们的轨道。

今天科学家们描述宇宙根据两个基本部分的理论——广义相对论和量子力学。他们是伟大的知识成就一位半个世纪。广义相对论描述的重力和宇宙大尺度结构的,即结构尺度从只有几英里,大如一百万(1与0后)英里,可观测的宇宙的大小。量子力学,另一方面,处理现象非常小的尺度上,离子如1000000英寸。然而,不幸的是,这两个理论是已知的不一致——他们不可能都正确。一个主要的努力在今天的物理学,是寻找一个新的理论,我们可能仍然是一个很长的路从拥有一个,但是我们已经知道许多属性,它必须有。