Towards a Unified Cosmology
Cosmology is a difficult subject, not only because of the nature of its
subject-matter but also because the methods of approach are of a kind with which we are quite unfamiliar in other branches of science, but even among works on cosmology the present book is a difficult one to review.
The main difficulty is the author’s insistence on the “Principle of Minimum Assumption”. His hypothesis, which is really a hypothesis on the philosophy of science but which he considers to be also a truly scientific hypothesis because he can confirm it in a number of cases, is that in physics the minimum assumption always constitutes the true generalization.
As an example, by the minimum assumption for the number of planets in the solar system is meant the unspecific assumption that any number of planets can occur. Now, it is quite possible to call this the minimum assumption if the author so wishes, but this procedure of making the minimum assumption is diametrically opposed to the method actually employed in science, and to the method which many philosophers of science think should be employed, for the minimum assumption is the very hardest one to refute. But many of us believe that the best assumption is is the one which lays itself open most readily to possible refutation. However, by means of this hypothesis of the minimum assumption, the author was led to the conclusion that a satisfactory cosmological theory requires a continuous creation and annihilation of matter, and he was led to this before the Cambridge cosmologists postulated the continual creation which leads to the steady state theory. It is puzzling that his assumption should lead to a conclusion which is not so very different from the one to which the Cambridge cosmologists were led by exactly the opposite view, that is, by looking for the most refutable assumption.
The author does not deal very fully with the difficulty that annihilation of matter may well lead to experimental effects which have not been observed: for example, to the half-life of the proton which one would expect to be able to measure. But I do not wish to be altogether critical of the book. There are many interesting flashes of insight scattered about it, notably a discussion about gravitation. The author lists a set of problems about gravitation: for example, Why should there exist a field which tends to increase its sources, unlike every other field which tends to decrease them (because like masses attract)? Why, indeed, do like masses attract, and why have we only ever found positive gravitational masses? Why does the inertial mass always occur in association with an active gravitational mass (if, as I would accept, the general theory of relativity merely incorporates the equivalence of inertial and passive gravitational masses?) Why is there only a limited number of constant ratios between unit charge and the inertial mass of the elementary particles? Can one reconcile what is known about gravitation with action at a distance? All these seem to me questions which are worth asking at this particular time.
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