Radioactivity: Lecture I-V

The science of radioactivity has now reached a stage in its development at which we can speak of it with a good deal of confidence. Among those who feel a keen interest in the recent developments of science, but who have not had time to follow them in detail, and it is to such that I was asked to address these lectures, there is a rather prevalent feeling that the discoveries in this branch of physics and chemistry have been of a revolutionary character. One often hears the opinion expressed that the discoveries in radioactivity have completely overthrown many of the theories that we had come to look upon as firmly established. In particular, I have often been asked about the validity of the principle of the conservation of energy — the fundamental principle of the physical sciences — in the light of the phenomena of radioactivity. Can we still build upon that principle? What I shall attempt in these lectures is to show how far our old notions of the constitution of matter are still valid, what modifications we must make in them, and where the physical sciences stand at present in the light of the discoveries that have been made during the 17 years that have elapsed since the discovery of radioactive phenomena. I hope to succeed in showing you that the results that have been obtained are much more constructive than destructive in their effect upon our views as to the constitution of matter. Instead of being revolutionary in their tendency they lead, viewed in a certain way, to a logical development of the physical sciences; for these discoveries give us information about the interior structure of the atom about which everything was largely conjecture. We are at only the beginning of what is bound to lead to a much fuller conception of atomic structure. The foundation for it has been built up, and it is this foundation that I wish to describe to you.