The discovery of radioactivity created a momentary chaos in chemistry and physics; but it soon led to a fuller interpretation of the old ideas. It dispersed many difficulties, harmonized many discords, and — yea, more! It shewed the substance of Universe as a simplicity of Light and Life, manners to compose atoms, themselves capable of deeper self-realization through fresh complexities and organizations, each with its own peculiar powers and pleasures, each pursuing its path through the world where all things are possible.

We must not forget that when radium was discovered no one knew that it would prove useful in hospitals. The work was one of pure science. And this is a proof that scientific work must not be considered from the point of view of the direct usefulness of it. It must be done for itself, for the beauty of science, and then there is always the chance that a scientific discovery may become like the radium a benefit for humanity.

In the progress of ordinary research the discovery of radium by Madame Curie in the year 1902 put an entirely new face upon the subject of electrons. The beta particles emanating from radium were soon identified with the electrons of the cathode ray. Then followed the discovery that the gas helium, previously treated as a separate element, evolved itself as one consequence of the disintegration of radium. Transmutation, till then laughed at as a superstition of the alchemist, passed quietly into the region of accepted natural phenomena, and the chemical elements were seen to be bodies built up of electrons in varying number and probably in varying arrangements. So at last ordinary science had reached one important result of the occult research carried on seven years earlier. It has not yet reached the finer results of the occult research—the structure of the hydrogen atom with its eighteen etheric atoms and the way in which the atomic weights of all elements are explained by the number of etheric atoms entering into their constitution.

In the progress of ordinary research the discovery of radium by Madame Curie in the year 1902 put an entirely new face upon the subject of electrons. The beta particles emanating from radium were soon identified with the electrons of the cathode ray. Then followed the discovery that the gas helium, previously treated as a separate element, evolved itself as one consequence of the disintegration of radium. Transmutation, till then laughed at as a superstition of the alchemist, passed quietly into the region of accepted natural phenomena, and the chemical elements were seen to be bodies built up of electrons in varying number and probably in varying arrangements. So at last ordinary science had reached one important result of the occult research carried on seven years earlier. It has not yet reached the finer results of the occult research—the structure of the hydrogen atom with its eighteen etheric atoms and the way in which the atomic weights of all elements are explained by the number of etheric atoms entering into their constitution.

The history of can be considered nothing less than a huge triumph for science. Over the course of a little more than a century of effort, our understanding of the world of atomic and subatomic physics went from a vague understanding of atoms, to one that is much more detailed. Early in this hundred-year-long period, we learned about electrons (1897), then how they circle a dense nucleus (1911), followed by the discovery of the s (1917) and s (1932) that form the nucleus. From the 1930s onward, researchers used both cosmic rays and particle accelerators to discover antimatter (1932), and particles that don’t exist in atoms (e.g., the and , as well as a huge number of others).

in the forty-five years centered on 1910, the nature of the atom was first understood — partly by shooting pieces of atoms at atoms and watching how they bounce off.

We were able to discover two new kinds of atomic species, one was hydrogen of mass 3, unknown until that time, and the other helium of mass 3, also unknown. … We were able to show that heavy hydrogen nuclei, that is to say the cores of heavy hydrogen atoms, could be made to react with one another to produce a good deal of energy and new kinds of atom. …Of course, we had no idea whatever that this would one day be applied to make hydrogen bombs. Our curiosity was just curiosity about the structure of the nucleus of the atom, and the discovery of these reactions was purely, as the Americans would put it, coincidental.

Knowledge of the components of the atom and of the forces that hold them together stimulated entirely new fields of basic science and technology that continue to the present.

Radioactivity is shown to be accompanied by chemical changes in which new types of matter are being continually produced. … The conclusion is drawn that these chemical changes must be sub-atomic in character.

The discovery by Monsieur and Madame Curie that a sample of radium gives out sufficient energy to melt half its weight of ice per hour has attracted attention to the question of the source from which the radium derives the energy necessary to maintain the radiation; this problem has been before us ever since the original discovery by Becquerel of the radiation from uranium.

At the time I was brought into the picture, research on the uses of atomic energy had been going on at a gradually accelerating pace since January, 1939, when Lise Meitner explained that the uranium atom could be split. The discovery opened up two divergent paths for its exploitation. Most physical scientsts realized that nuclear energy, derived from the splitting, or fissioning, of the atom, might be used either to generate power for peaceful purposes or to generate super-weapons. In general, however, it was the scientists who were personally acquainted with Hitler's New Order who first became most interested in the possible military uses of atomic energy and its effect on the existing balance of political power.

A theoretical investigation which Einstein published in 1917 provides a third conspicuous landmark. It connected up he two great landmarks already mentioned by showing that the disintegration of radioactive substances is governed by the same laws as the jumps of the kangaroo electrons in the theory of Bohr. In fact radioactive atoms were now seen merely to contain a special breed of kangaroos, much more energetic and ferocious than any that had hitherto been encountered.

Atoms were originally proposed as an idea. Although their presence was proved by various means, people did not think that they could see them directly. This was so until recently. We are now able to directly see atoms by employing powerful microscopic techniques.

Rutherford's discovery was the beginning of the science that came to be called nuclear physics. ... The projectiles that he used to explore the nucleus were particles produced in the disintegration of radium ... discovered by Marie Curie in 1898. The particles are helium nuclei that are emitted at high speed when radium atoms decay ... The twenty years between 1909 and 1929 were the era of tabletop nuclear physics. ... Small and simple experiments were sufficient to establish the basic laws of nuclear physics.