Context and sources: “Ancient and Modern Atomic Theories”

The old saying that there is nothing new under the sun appears at first glance to find another bit of corroborative evidence in the case of atomic theories. Superficially it would seem that in its latest developments modern science has only returned to the ancient theories of Democritus and the Atomists. In fact when compared with the theories prevalent up until four decades ago the Greek materialism has many important suppositions in common with the later theories. That the Greeks developed a conception of matter approaching in any way the present ones, which have been arrived with experimental devices and mathematical knowledge far beyond those in the possession of the ancients, is a tribute to their own theory that, in the search for knowledge, reason is superior to perception.

…

Previous theories, Greek and otherwise, of the indestructibility and indivisibility of the atom and its related causes have undergone some revolutionary changes in the last three decades. Democritus proved the indestructibility by postulating perfect solidity and no internal space. Therefore since space is necessary for motion and change the atom could not possibly break up. Today even with the admission of comparatively vast spaces in the atom it would be possible to maintain a theory of indestructibility if it were not for our discovery of the radioactive elements such as radium, which spontaneously disintegrate themselves and whose radiations cause other elements to break up. Actually a fragment of the atom shoots out and in shooting into another atom may create a third kind by dislodging some section. No doubt these facts would have had a disturbing effect on Democritus if they had been demonstrated to him. Today It seems that the electron and the unit proton must be the ultimate indivisibilities.

Modern theories of combination - the molecule - the question of valence - can only be held in the light of the electron theory and with knowledge of electrical charges and the forces connected with them. For this reason the Greeks could have had no idea of chemical combination as we know it. Their atoms were self-sufficient, although capable of combining by a sort of frictional cohesion. Solid matter was for them composed of rough catchy atoms which hooked upon each other hindering motion and producing solidity. Liquids and gases were comprised of a collection of atoms with the properties of ball bearings. Such a conception is very unsimilar to the modern one which supposes an interchange and sharing of electrons.

…

To Democritus the problem of what was to be found between the atoms presented no difficulties. “Nothing” was the answer, void, empty space. In fact vacancy was absolutely necessary for his motion. Later physicists have found it difficult to accept this simple answer. Undulatory phenomena seemed to demand a medium, so the “ether” a sort of elastic, frictionless, inertialess continuum was postulated. Of late the necessary properties of this medium have been much under discussion. It is an hypothesis to which physicists are forced in order to explain certain phenomena undetectable until very recently. Because of its very omnipresence it is difficult to determine anything about it. The whole science of wave mechanics and the ether offers problems which were not dreamed of, and of course not allowed for, in Democritus’ time.

Such in brief are the relations of the two theories in respect to the specific properties that Democritus outlines. There is in many cases surprising similarity, and yet the actual conceptions are very different. The really remarkable fact is that the early theory was ever atomic at all. When well considered it seems that Democritus achieved half the way to modern science by formulating that theory in the first place. Not till Faraday was the second big step begun. Then began the realization of the electrical nature of the atom.

There was a solid particle. Here we have an entity, chiefly space filled with motion, filled in the sense in which the space around a revolving sprinkler is filled, but with the actual matter as scarce as a planet in the solar system. Two electrical powers pull and balance each other. All is force and motion - and waves, waves which are still an enigma.

There is one point more of difference. Democritus could only reason that there were atoms because that seemed to him the best explanation of the universe, out even reason, of this type, may be fallible as Herecleitus and Parmenides showed despite themselves. But science today knows, can prove, at least, its basic hypothesis. These will remain. We can have confidence that the system for which Democritus laid the foundations, although it will undergo many modifications and amplifications, will never be completely destroyed.