WHAT IS MATTER?

New Zealand Herald, Volume LXIII, Issue 19221, 9 January 1926, Page 1 (Supplement)

WHAT IS MATTER?

OLD VIEWS AND NEW.

BY N. A. WINTER B.A. (LONDON)

Men's minds have tried —probably since the first dawn of reason —to pierce the constitution cfi things, and the earliest written records that have come down to us are full of their speculations. We have in the great poem of Lucretius, "De Rerum Natura," an exposition of the views held by one school of Grecian philosophers on the Nature of Things. These men by an exercise of sheer thought, unaided by any experimentation, arrived at a theory which has a startling resemblance to the modern chemical theory of matter. According to them, there exist atoms (primordia) which are in their nature solid, indivisible, eternal, and which, by their combinations, produce everything recognisable by our

senses. Another doctrine was that all things consist of four elements, earth, air, fire and water. This theory persisted almost to our own day. For centuries during the middle ages, the study of alchemy was pursued with feverish energy, the dream of the alche-mists-being to transmute base metals into gold. To Dalton we owe the credit of having discovered the true laws of chemical combination. According to him, every substance consists of ultimate par,tides which, if the substance is a compound one, contains two or more constituent particles incapable of further subdivision. The compound particle 1 he called a molecule, and the final indivisible particle ho called an atom. For example, water consists of ultimate particles each of which is resolvable into other particles of two different kinds. In other words the molecule of water can be separated into a.oms of oxygen and hydrogen respectively. Complexity ol tlie Atom. The moderns, in possessing instruments of extreme precision, have a great advantage over the ancients. What the telescope has done for astronomy, bringing un-dreamt-of regions of space in human ken, the microscope, and particularly the ultramicroscope, has done for chemistry. But as there are depths of space which can never be brought within our vision, so there are forms of matter so extremely small that they can never be brought into the field of sight. Man floats, as has been said, between two infinities, the infinitely great and the infinitely little. The atom was for many years regarded as a simple thing, impossible to resolve into parts. Recently, however, following oh the discovery of radium, certain amazing facts have been found out about the atom which prove absolutely that it is by no means a simple thing, but, on the contrary, extremely complex. The constitution of the atom is in fact comparable to that of the solar system, but on a scale so minute that one's imagination flags in trying to realise it. When one reads of electrons whirling round a central nucleus in an orbit, whose radius is the millionth part of- a millimetre, and at a speed nearly equal. to that of light, one is first inclined to question the conclusions of the scientists. But just as surveyors can measure the distance between the tops of Rangitoto and Mount Eden by means of; observations, far more accurately than we could measure the' breadth of a room by means of a 2ft. rule, so the scientists can, by indirect methods, measure the minutest distance with absolute accuracy. s An Interesting Experiment. It will be interesting to describe one experiment—an extremely brilliant one—by which the diameter of a molecule of oil was ascertained. Oil poured on pure water sppfads until the molecules are kept from further extension by cohesion alone, and consequently the thickness of the film is the diameter of a molecule of oil. Now many attempts, more or less successful, were made to measure this thickness, but the method devised by Professor Millikan, of Chicago, was a perfect triumph of thoroughness and simplicity. He arranged on a stand a round copper vessel pierced by a minute hole at the bottom. Above and below the air space in the frame supporting the vessel were metal plates connected with an electric battery by means of which measured currents of electricity could bo sent on to the plates. An apparatus was arranged so as to throw a very strong beam of light through the air space above-mentioned. A telescope was also levelled on this. Just as motes are visible in a sunbeam, so minute objects illuminated by the electric beam would be visible through the telescope. The next step was to spray some oil in the form of into the vessel by means of an atomiser. When this condensed one drop would fall through the little hole and descend through the air space. On account of its lightness it would move somewhat slowly, and by means of the plates either a positive or a negative charge could bo communicated to it. The one would retard and the other accelerate its pace. In fact the operator controlled the movements of the drop as one would control by reins the movements of a horse. Briefly, the mass and volume of the tiny drop of oil were ascertained. Next the drop was made to fall on a vessel of pure water. It spread out, of course, but into such an attenuated film that it was not easy to observe its outline. A certain metallic lustre often forms a rough indication of this, but something more accurate was' needed. It was known that talc powder if sprinkled on pure water may be blown completely off its surface, but that it will adhere to oil. This property was utilised for the experiment, and when the powder was strewn over the vessel and blown upon, the water beyond the film became clear, but the film remained white. Its extent could therefore be accurately found, and it became a question cf simple arithmetic to ascertain its thickness, the volume of the drop of oil being known. This is only one example of the ingenuity with which these investigations are pursued. The Alphabet of Nature. It is impossible in a short article to give even a sketch of the methods by which the constitution of the atom was ascertained. Let it suffice to say that by several independent lines of research, including the use of spectrum analysis, it has been shown that, while the atoms of the chemical element are of an ascending order of complexity, they all consist of only two kinds of"things, one of which Rutherford calls a proton and the other of which is known as an electron. The atoms differ from each other according to the number of protons and electrons they contain and according to the gyrations of the latter around the central core or nucleus. The older chemistry taught that all material things in this earth were composed of a certain (comparatively small) number of elements, just as a language with its mighty range is made up of a fixed number of letters. (Lucretius himself, by the way, uses this illustration.) The newer chemistry shows us that the analysis can be pushed much farther back". The final elements seem to be only the proton and the electron. The alphabet of nature is, as it were, reduced from about ninety letters to two. Moreover, the complex atom of radium can be actually watched as it disintegrates, and, like Proteus of old or the "lightningchange " artist of the modern stage, transform itself into other substances, some of which by devious roads convert themselves into lead. Thus the old view fuses into the new and the dream of the alchemist becomes the reality of modern science.