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COSMOLOGY OLD AND NEW
How do theories arise? How is our mental picture of the world which surrounds us formed and developed? Do we obtain at first a rough sketch, a faint outline, which, as we proceed, gains in clearness and firmness and gathers new and bright colours whilst retaining the stamp and character of the original outline? In other words, is the development of a theory merely a process of evolution, or do there occur cataclysms, great revolution, which in a short space of time transform our whole physical outlook?
In the history of scientific development we discern both these processes the evolutionary and the revolutionary. Evolution is the outcome of the collective efforts of generations, of the brilliant successes of illustrious men, and of minor but useful labours which serve to amplify our theoretical ideas; it is the gradual building up of the structure of science on foundations which have already been laid. In the course of evolution great ideas grow and mature, theory is freed from assumptions, whose extreme simplicity cramps the theory, the range of facts which the theory covers gradually widens and the originally simple mathematical form of the theory becomes at the same time more complicated and far-reaching.
We shall doubtless never succeed in understanding fully the reality which surrounds us. Nowadays, we are conscious that our feeble efforts and unskilled attempts to grasp the laws of Nature become constantly outstripped by the complexity of the phenomena observed in the world of ours. As a theory develops, there may appear in it some minor flaws which may remain unnoticed in the triumphal progress of the theory, only however, to manifest themselves more clearly and menacingly later on. Difficulties of this kind, disagreement between deductions from the theory and the results of experiment, inconsistencies and even vital contradictions which cannot be explained away by the theory-these often contain the seeds of fresh developments by making it necessary to enunciate new principles and to re-lay the foundations of science. When a theory is frustrated in this manner the ground is prepared for a scientific revolution. This is nearly the work of one great mind. Such a revolution involves the transfer of problems to a new sphere of investigation, it forces us to consider the scientific phenomena in a different light, and it lays a fresh foundation upon which we proceed to build a new and different world of physics."
