How Does Radioactivity Work?

The emission over, and the fragment of the atom gone, the residue is no longer radium, but is something else.

Continuing Early Science of Radioactivity,
with a selection from Presidential Address to the British Association for the Advancement of Science by Sir William Ramsay published in either 1911 or 1912. This selection is presented in 3 installments, each one 5 minutes long. For works benefiting from the latest research see the “More information” section at the bottom of these pages.

Previously in Early Science of Radioactivity.

Time: 1903
Place: Paris

The emission over, and the fragment of the atom gone, the residue is no longer radium, but is something else. What it is we do not yet know; but since it is produced in isolated atoms here and there, with crowds of foreign substance between, there is no cohesion or any continuity between its particles; they are separated like the atoms of a gas, or like the molecules of a salt in a very dilute solution in which there are millions or billions of times as many atoms of the solvent as there are of the dissolved salt. So they are easily carried away by any motion of the medium in which they are mechanically embedded; but they retain their individuality, and their radioactive power persists, because the breaking-up process is by no means finished, stability is far from attained : indeed, the instability is more marked that it was in the original substance ; for whereas in the original substance only one single atom here and there out of a million of millions was affected by it, here in the diffusing emanation or first product of incipient atomic dissociation every atom seems unstable or at least to be in a very critical condition. So that in a time to be reckoned in minutes or days or months (according to the nature of the emanation, whether it be from thorium or radium, or uranium), a further breakdown has occurred in every atom; and so its accompaniment of radioactivity ceases. The radioactive power has disappeared from the emanation, but it has not wholly ceased : it has been transferred this time to a solid deposit which has been the residual outcome of the second break-up. For the atoms of this deposit also are unstable and break up, in a time which can be reckoned in months, days, or minutes, apparently in roughly inverse order to the duration of the parent emanation. Another and another substance has also been suspected, by Rutherford and Soddy, as the outcome of this third break-up; while gradually the radioactive power of the resulting emanations becomes imperceptible, and further investigation by present methods becomes impossible for lack of means of detection of sufficient delicacy.

Here, then, we appear to have, in embryo, a transmutation of the elements, the possibility of which has for so long been the guess and the desire of alchemists. Whether the progress of research will confirm this hypothesis, and whether any of the series of substances so produced are already familiarly known to us in ordinary chemistry, remains to be seen. It is not in the least likely that any one radioactive substance can furnish in its stages of collapse the whole series of elements; most likely one substance will give one series, and another sub stance will give another; and it may be that these emanations are new and unstable elements or compounds such as are not already known, or it may be that they approximate in proper ties to some of the known elements without any exact coincidence. The recognized elements which we know so well must clearly be comparatively stable and persistent forms, but it does not follow that they are infinitely stable and perpetual; the probability is that every now and then, whether by the shock of collision or otherwise, the rapidity of motion necessary for instability will be attained by some one atom, and then that particular atom will fling off the fragment and emit the rays of which we have spoken, and begin a series of evolutionary changes of which the details may have to be worked out separately for each chemical element.

If there be any truth in this speculation, matter is an evanescent and transient phenomenon, subject to gradual decay and decomposition by the action of its own internal forces and motions, somewhat as has been suspected and to some extent ascertained to be the case for energy. If it be asked, “How comes it, then, that matter is still in existence? Why has it not already all broken down, especially in these very radioactive and therefore presumably rapidly decadent forms of radium and the like?” the question naturally directs us to seek some mode of origin for atoms, to conjecture some falling together of their pristine material, some agglomeration of the separate electrons of which they are hypothetically composed, such as is a familiar idea when applied to the gravitational aggregates of astronomy which we call nebulae and suns and planets.

We may also ask whether many other phenomena, known but not understood, are not now going to receive their explanation. The light of the glowworm and firefly and other forms of life is one thing which deserves study; the Brownian movements of microscopic particles is another. Are we witnessing in the Brownian movements any external evidence, exhibited by a small aggregate of an immense number of atoms, of the effects of internal rearrangement and emission of the parts of the atoms, going on from the free surface of the particle? And can it be that the light emitted by the glowworm — which is true light and not technical radioactivity, and yet which is accompanied by a trace of something which can penetrate black paper and affect a light-screened photographic plate — is emitted because the insect has learned how to control the breaking-down of atoms, so as to enable their internal energy in the act of transmutation to take the form of useful light instead of the useless form of an insignificant amount of heat or other kind of radiation effect; the faint residual penetrating emission being a secondary but elucidatory and instructive appendage to the main luminosity?

Many more questions may be asked and if the conjectures now rife are to any great extent confirmed, it is clear that many important avenues for fruitful experimental inquiry will be opened up. Among them an easy and hopeful line of investigation, lying in the path of persons favorably situated for physically examining the luminous emission of live animals, may perhaps usefully be here suggested.

And let me conclude by asking readers to give no ear to the absurd claim of paradoxers and others ignorant of the principles of physics, who, with misplaced ingenuity, will be sure to urge that the foundations of science are being uprooted and long-cherished laws shaken. Nothing of the kind is happening. The new information now being gained in so many laboratories is supplementary and stimulating, not really revolutionary, nor in the least perturbing to mathematical physicists, whatever it may be to chemists; for on the electric theory of matter it is the kind of thing that ought to occur. And one outstanding difficulty about this theory, often previously felt and expressed by Professor Larmor — that matter ought to be radioactive and unstable if the electric theory of its constitution were true — this theoretical difficulty is being removed in the most brilliant possible way.

Mme. Marie Curie begins here. Sir William Ramsay begins here. Sir Oliver Lodge begins here.

More information here and here, and below.

We want to take this site to the next level but we need money to do that. Please contribute directly by signing up at https://www.patreon.com/history