The Origin and Development of the Atomic Theory

CHAPTER I. The Pythagorean Atomists

THE PYTHAGOREAN ATOMISTS

THE SIGNIFICANCE OF THE ATOMIC THEORY

It is safe to say that there is no more romantic story in the history of science than that of the origin and development of the atomic theory of matter. Dr. Robert A. Millikan has said that the physical principles laid down by Leucippus in the fifth century before our era might, with a few modifications and omissions, “almost pass muster today” (“The Electron,” Page 7). The importance to modern students of sound knowledge of the teachings of the ancient Atomists was emphasized by Sir William Osler (1829-1919), who even went so far as to say that “the student of physics may know Crookes’ tubes and their relation to Roentgen, but he cannot have a true conception of the atomic theory without a knowledge of Democritus; and the exponent of Madame Curie and of Sir J. J. Thomson will find his happiest illustrations from the writings of Lucretius”--the Roman exponent of Epicurus (342-270 B. C.), who revived the atomic theory of Leucippus and Democritus, despite the adverse criticisms hurled at this doctrine by the great Aristotle.

Le Sage observed that “if Epicurus had had but a part of the geometrical knowledge of his contemporary Euclid, and conceptions of cosmogony the same as many then living, he might have discovered the laws of universal gravity, and not only the laws, but, what was the despair of Newton, its mechanical cause” (“Lucrèce Newtonien,” Berlin Academy, 1782).

Writing of the value to science and modern thought of the atomic theory of the early Greek philosophers, Professor Walter T. Marvin, of Rutgers College, points out that a theory can be significant in at least three ways, namely:--“(1) by destroying or inhibiting other beliefs; (2) by arousing interest in new problems and by suggesting new methods of investigation; (3) by what it itself enables us to explain correctly. This theory was most significant in destroying old beliefs or, to adopt a much used expression, in ‘enlightening’ the cultured Greeks. A thoughtful Greek could hardly believe that the universe is a cloud of atoms moving about in accordance with necessary mechanical laws, and at the same time continue to believe the primitive traditions and superstitions of his people. The worship of the gods and the old magical rites and ceremonies must needs seem to him utterly ineffective and useless, valuable customs no doubt for their purely psychological influence upon the ignorant and unruly masses but of course absurdities for the cultured and disciplined man. Hence no wonder that the spread of this and the preceding cosmological theories would result, in a society such as that of the Greek world in the sixth and fifth centuries B. C., in a radical enlightenment. No wonder that their spread was opposed by men of conservative tendencies. In this first respect early Greek science and in particular the atomic theory were of great historical significance.”

THE ATOMIC THEORY OF THE PYTHAGOREANS

In the ancient Sanskrit literature of India (written prior to 500 B. C.), an atomic theory of matter is formulated by Kanada (literally “atom eater”--a term of derision), founder of the Nyaga system of philosophy, and said to have been a pupil of Buddha. He states that the atoms are eternal and that the ultimate atom is simple.

Kapila, the leading exponent of the Sankhya philosophy, speaks of “five subtle” kinds of particles (atoms), and a substance akin to our luminiferous ether--the five particles being, no doubt, the “five elements” of the Laws of Menu; viz., earth, water, wind (air), fire and ether--this last the parent, so to speak, of all the other elements, through a process of successive transformations.

In the “Angutarra Nikaja,” consciousness (mind) is mentioned as a sixth element, also atomic in structure.

In his “History of Hindu Chemistry,” Sir P. C. Ray expresses the opinion that the atomic theory of the ancient Greeks was derived directly from the more ancient Hindu doctrine--a view upheld by the great German Sanskrit scholar, Dr. Max Müller, as also by some Greek scholars.

The atomic theory, the earliest known to have been worked out in detail, is that of the Greek philosopher Leucippus, of Miletus, Ionia; though the mantle of honor has fallen mostly on the shoulders of his far better known pupil, Democritus of Abdera, Thrace.

But the Pythagoreans also were exponents of a form of atomic theory, and it seems probable that Pythagoras, a native of the island of Samos, was the first Greek to advance the doctrine of the discontinuity of matter. At least, none of his disciples ever claimed to have been the originator of this doctrine, and Pythagoras was born some time between 580 and 570 B. C., while the Atomic School of Leucippus was not founded until some time after 500 B. C. Unfortunately, Pythagoras did not commit his doctrines to writing, though a few of the so-called “Golden Sentences” may have been written by him. Most of them, however, are probably no older than the fourth century of our era. Moreover, these throw no light on the subject under discussion.

The first written exposition of the Pythagorean atomic theory was put forward by Philolaus, a native of Tarentum, South Italy. Only fragments of his work have survived, and of those ascribed to him some are undoubtedly spurious. But all of them are very old and contain valuable information concerning Pythagorean doctrines.

Porphyry (233-304? A. D.), a Syrian Neo-Platonist, residing for some years in Alexandria, wrote a “Life of Pythagoras,” and a few years later another “Life” of this philosopher appeared, this time from the pen--or stylus--of another Syrian and Neo-Platonist, Iamblichus. But these works contain much that is wholly mythical concerning Pythagoras.

Our best sources of information are Plato (Timaeus), Aristotle (Metaphysica and Physica, De Anima and De Caelo), Diogenes Laertius (De Vitis) and Stobaeus (Eclogarum physicarum et ethicarum). From these authorities we learn that, according to the Pythagoreans, the cosmos was at a certain stage of its (cyclic) changes a compact, inert, spherical mass of lifeless matter, having no distinguishable parts. After a long period of quiescence the “void”--i. e., the limitless outer air--broke in upon the world, entering into “the heaven itself” as if it--the heaven--were breathing. The result of this cosmic inhalation was “a certain separation and definition of things that lie together” (Aristotle, Physica, iv, 6)--that is, a separation of the homogeneous mass into different “elements.” These fragments were eventually ground into an all but infinite number of infinitesimal particles, or “monads,” analogous to the “atoms” of Leucippus and Democritus.

Now, Philolaus was a famous geometrician as well as an eminent physician and astronomer. Hence he--and presumably Pythagoras before him--thought of these particles (or atoms) not in terms of various qualities, chemically considered,--as Anaxagoras (500-428 B. C.), who was not a Pythagorean, had done before Philolaus wrote--but in terms of form (shape) and number. Each of the various substances known to the ancient world as “elements”--generally recognized as compounds of the real elements since the eighteenth century only--was regarded as made up of particles of a certain geometrical configuration. Philolaus explained that the “element” earth was composed of cubical particles, fire of tetrahedra (pyramidal forms), and the “ether” was identified with the dodecahedron (particles having twelve plane faces, or twelve regular pentagons). In the Timaeus of Plato we find this conception further developed, bringing all the five regular solids into the theory. Thus, the octahedron was now assigned to air, and the icosahedron (a figure having twenty equilateral triangular faces) to water.

Very interesting in this connection is the fact that the positions of the electrons in atoms (the real elements) are being referred to today in terms similar to those employed by the Pythagoreans. Take, for example, the following passage from Science Progress (London), July, 1922 (No. 65), Pages 21-22:

“The modifications proposed in the expressions for electric and magnetic forces allow of the electrons in [Sir J. J.] Thomson’s model [atoms] to take up positions at rest at the corners of certain well-known polyhedra, such as the tetrahedron, the cube, the rhombic dodecahedron, the cubo-octahedron; and so in the sharing of electrons between atoms and the consequent fitting together of such models we have the explanation of certain facts of crystallography.”

But we know now that “fire” is not an “element” composed of tetrahedral atoms; but the combustible portion of coal and wood is the real element carbon--and the carbon molecule is of tetrahedral form. (See Bragg, Sir W. H. and W. L., “X-Rays and Crystal Spectra.”)

On the Pythagorean theory--as on that of Leucippus, and on the latest theories of today--matter is broken up into parts (atoms) that are in themselves unchangeable--apart from radioactivity--but produce by their changes of position in relation to one another all the substances of earth and of living organisms.

To illustrate this principle in terms of modern science: Add four electrons (two positive and two negative) to the hydrogen atom, and you have the element lithium; knock out of the lithium atom (composed of three positive and three negative electrons) one positive and one negative electron, and you have one atom of helium (composed of two positive and two negative electrons.) And electrons are all alike, except that some carry a charge of positive electrification and some a negative charge--each kind (species) of atom having an equal number of positive and negative charges, thus attaining stable equilibrium. (See Soddy, The Interpretation of Radium, 1922.)

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