Abstract
IN the Sir Halley Stewart Trust Lecture delivered on October 24, Sir William Bragg said that an important factor in the rapid progress of science, so marked in recent years, has been the discovery that in one of her chief aspects Nature's constructions are essentially ‘particulate’. In the first place, matter is particulate. The atomic theory as now understood dates from the time of Dalton, who established the fact that atoms, of a limited number of kinds, combine in definite numerical proportions to form the substances of the world. This great generalisation is the foundation of chemistry. Forty years ago it was shown that electricity is also particulate, the ultimate unit, when of negative sign, being called the ‘electron’. These two generalisations have prepared the way for a third; it has been found that energy may also be described as ‘particulate’. The transfer of energy is effected in units, known as ‘quanta’. It is now possible to demonstrate the single atom, though a hundred million in line cover only an inch, the single electron and even the single energy quantum. Accurate maps of various molecules can be drawn, showing the signs and positions of the atoms of which they are composed: just as an architect draws the plan of a building. We may study the single ring of six carbon atoms which, with attached hydrogens, forms the molecule of benzene, or the double ring of naphthalene and the treble ring of anthracene, these being of great importance in the dye industry; or the five-ringed structure which is typical of most of those substances that are known to produce cancer. We can examine the details of the long protein molecule which plays so great a part in animal life, or the cellulose molecule of plants, or the arrangements of the atoms in metals and rocks. Nature builds all the substances that we know on certain definite structural lines. It is because we have learnt this fact, and are learning how to follow, very haltingly it may be, that physical science is making such rapid headway.
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The New Physics. Nature 136, 711 (1935). https://doi.org/10.1038/136711c0
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DOI: https://doi.org/10.1038/136711c0