190 



Supplement to '*Natu7'e,'' August 4, 1923 



WiLBKRFORCK MoDEL. 



1 1 rii;i\ l>c said that if we depend on the pressure 

 of hght as conveying energy, it is a longitudinal 

 phenomenon ; whereas an electron is probably a 

 rotatory or rotational phenomenon. Or again, if we 

 attend to the magnetic oscillation in the beam of 

 light, and consider that the electric oscillation is 

 separated from it, or neutralised, by matter, that 

 still there is nothing of the rotational kind about it. 



One answer would be that circularly polarised 

 light clearly has a rotational aspect. Another and 

 more fundamental answer would direct attention 

 to the transition, or interchange, that may go on 

 between a linear oscillator and a rotational oscillator 

 when they are of the same frequency, or properly 

 attuned. 



In illustration of that, I would invite attention to 

 the illustrative models constructed by Prof. Wilberforce, 

 my successor in the chair of physics at Liverpool, 

 which show that a continual interchange of energy 

 between a linear vibration in one direction, and a 

 rotational vibration in a plane at right angles, natur- 

 ally goes on when the two modes are synchronous. 

 Thus the energy alternately takes first one form and 

 then the other ; and then back again, without inter- 

 mission. 



Of course the dynamics of the model is thoroughly 

 understood, and Wilberforce himself has explained it, 

 that is, has recorded the relevant equations ; ^ and 

 in that sense there is nothing puzzling about it, though 

 its behaviour can be made to look rather paradoxical. 

 But I feel that there is some meaning underlying the 

 possibilities here indicated, which are not yet com- 

 pletely exhausted, and that they may, when more 

 deeply considered, throw some light upon the inter- 

 action between electricity and magnetism — if that 

 should still be necessary, — and possibly on the inter- 

 action between ether and matter, and perhaps between 

 waves and electrons, where more information is certainly 

 necessary. At any rate, I regard the behaviour of 

 the model as suggestive, and am content for the present 

 to direct attention to it, from this point of view. 



Origin of Electrons. 



Let us assume, then, for a moment that there may be 

 some truth in the idea of a discontinuous wave-front. 

 To what are we led ? I should reply, that the motion 

 in a wave-front seems more akin to the kind of 

 motion that constitutes the discontinuous and isolated 

 speck that we call an electron ; and that the actual 

 generation of an electron by means of light is not an 

 altogether impossible idea. 



So I repeat the question : 



An electron suddenly set in motion generates light : 

 does light when it is suddenly stopped generate an 

 electron ? 



Sir William Bragg has often directed attention to 

 the singular relation existing between X-rays and 

 beta radiation. The impact of a beta particle emits 

 X-rays. The impact of X-rays emits a beta particle. 

 The energy of the original and the excited beta 

 particle are so closely proportional as to be practically 

 identical. It is as if the same beta particle, that is, 

 the same electron, had gone out of existence at one 



2 Phil. A fag., October 1894. 



place, and been recreated at another, the intermediate 

 link being constituted by sjxjcific radiation of a 

 perfectly definite wave-length. 



There is no need to assert that one particle has gon- 

 out of existence and the other come in ; and yet v. < 

 know of no reason for denying it. It may have t< 

 be denied, but I think it wise to keep an open mind 

 on the subject, however bizarre the notion may be. 

 There arc strange relations between energy and matter 

 now coming to the front. Matter contains intrinsi' 

 energy, as if it were something circulating with th< 

 velocity of light. There must be some meaning in 

 this. The ratio c^ between matter and energy is not 

 to be ignored. 



Somehow or other the ether possesses inertia. It 

 must, or it could not sustain magnetism, or account 

 for the increase of inertia due to motion. The ether 

 also contains an intrinsic and characteristic velocity, 

 which is perfectly definite. It is known that the vibra- 

 tions of vortices, and the speed at which a vortex 

 medium can transmit transverse waves, are closel\ 

 connected with the constitutional velocity of rotation 

 The two velocities are in fact equal, or connected b\ 

 a numerical factor, of a magnitude which some theorit 

 make -^2, but other theories make unity. In any 

 case the numerical factor is not far from unity. We 

 are justified in supposing that if the ether is full of 

 circulatory motion, that motion must be practically 

 the velocity of light. In that case, the fundamental 

 nature of matter would appear to be giving up its 

 secret ; and the relation between matter and energ\ 

 would be explained. 



There does not then seem any insuperable difficulty 

 about hoping that some future discover}' will be abl( 

 to generate matter, or at least to generate an electron . 

 by aid of X-rays or other form of radiation. I can 

 dimly conceive a theory of light which, when its advance 

 was stopped, should terminate not in the irregulai 

 jostle called heat, but in the regular circulation oi 

 vortex motion that we call an electron. The intimate 

 relation between energy and frequency associated witli 

 the quantum seems to me to negative the men 

 irregularity of thermal agitation, and to suggest 

 something quite regular and constitutional. 



We can go further, and can reckon how much 

 matter would be generated by a given amount of 

 luminous energy, if none of it were wasted as heat. 

 A beam of ordinary sunlight ten centimetres square 

 shining continuously, and supposed to be all converted 

 or interpreted as matter, would generate a weighablc 

 amount, namely one-tenth of a milligram, in seventeen 

 years. 



The density of sunlight near the earth is equivalent 

 to 2xio~^5 gram per second per square centimetre. 

 So if it were interpreted as matter, the earth would 

 catch 80,000 tons of it per annum. Of course, some 

 of it is wasted. Only radiation of the right frequency 

 is effective, just as only energy of the right frequency 

 is generated by a metrical impact. A lot of the 

 radiation may be due to irregular jostling, and this 

 portion when absorbed may result in heat. But it 

 is the more precise kinds of occurrence which are 

 instructive, and which must inevitably attract attention. 



I know that the Bohr Theory of the Atom seems 

 at first against these speculations. Electrons appear 



