Observational and Theoretical Astronomy

Abstract

ON April 28, Prof. H. H. Plaskett delivered his inaugural lecture as Savilian professor of astronomy at Oxford. Recalling the fact that the year of the foundation of the professorship was also that of the publication of Kepler's three laws of planetary motion, and directing attention to the injunction of Sir Henry Savile that the holder of his professorship should occupy himself with “observation by day and night”, he remarked that three hundred years ago the observational method in astronomy might be said to have reached its zenith. Since then, the constantly increasing importance of the theoretical method has been abundantly shown; as, for example, in the discovery of Neptune by calculation and in the present conclusions as to the physical conditions in the interior of stars. Nevertheless, the achievements of theoretical astronomy still rest in part on an observational basis. This is shown by consideration of the means by which knowledge of the spatial distribution of the stars has been gained by the work of Herschel and Shapley, and of that of their physical constitution by the work of Lockyer, Franklin and Hertzsprung. It would be fair to say, looking forward to the next three or four hundred years, that it will be allowed that, so far, observation and theory have gone along hand in hand. In a more distant future it may not be so. At present, theory has played its part in the refinement of observation, but some of the results of theory must for ever be removed from observational control. But just as the explorer of the earth's surface suggests to the geographer plans for further fruitful exploration, so the astronomer going to Nature with a definite theory may succeed in getting an answer. Finally, there can be no doubt that a great university should have an observatory as part of its equipment; but it must be recognised that the part of astronomy under these conditions necessarily has its limitations.