Contemporary Advances in Physics, XXXI - Spinning Atoms and Spinning Electrons

O doubt you are all accustomed to thinking of atoms as objects-- very small objects, of course--which are endowed with weight. I can say t h a t with perfect safety to an audience of engineers and physicists; b u t indeed it can be said with safety to any audience-- I mean, of course, any audience literate enough to attach any meaning at all to such a word as " a t o m . " It m a y be that philosophers of the past have imagined weightless a t o m s -- I am not historian enough to deny that, nor to affirm it; b u t if such have ever been invented, they have remained quite outside the currents of modern thought. For us, weight is a property which we attribute to the atom. Since this is, after all, a professional audience, I will now change over to t h a t other word which m a n y people have such difficulty in distinguishing from " w e i g h t " : I will say that mass is a property which we attribute to the atom. In a way, t h a t is a negative statement. It means t h a t we do not hope to explain mass in terms of something more fundamental; it means that we accept mass as being itself so fundamental that even the elementary particles have it. W h e n I say "elementary particles," I am still referring in part to the atoms, though it is a somewhat careless usage to do so; b u t I am referring also to electrons both positive and negative, to protons, to alpha-particles, to nuclei--to all the particles, in effect, of which the atoms are built up. Also I ought to include the corpuscles of light, b u t this lecture will be quite long enough if I leave them almost unmentioned.