COSMOLOGICAL HYPOTHESES. 



By R. T. A. INNES. 



The best known and still the most widely accepted 

 cosmological theory is Laplace's nebular hypothesis. 

 This hypothesis was only put forward in a tentative 

 manner by its author, although on several occasions 

 he recurred to the subject. It is proper to note that 

 although it is doubtful if anyone had ever a greater 

 facility for clothing his ideas in mathematical 

 formulas, Laplace used none in explaining the 

 nebular hypothesis. Many cosmogonies have been 

 based on ideas not essentially different from 

 Laplace's — that is, the condensation of a primitive 

 nebula into rings, which later disrupt into planets, 

 whilst the central and final condensation forms the 

 central body or sun of the system. The fission 

 theory of the formation of satellites and double stars 

 from condensing bodies is closely connected with 

 the nebular hypothesis. 



Other sets of cosmogonies are indicated under the 

 meteoric or planetesimal hypothesis, and capture 

 theory. Kant's cosmogony was more general in 

 that he postulated neither nebulous matter nor 

 meteors — merely matter. The nebular hypothesis of 

 Laplace, and its modifications by Faye, du Ligondes, 

 Darwin, See, and others, seized on the popular mind 

 because it was not in too marked discord with the 

 theological teachings of the age, " the earth was 

 without form, and void." Genesis i, 2. 



By the very mode of its existence the human race 

 can view but a small part of the drama of nature. 

 On the surface of the earth, thanks mainly to the 

 geological record, the mode of the evolution of flora 

 and fauna and the making of rocks is fairly clear. 

 But when we view not the surface of the earth, but 

 bodies outside the earth, the planets, stars and 

 nebulae, our interpretation is not so easy. We 

 cannot even say if the sun, and with it the earth, 

 is growing hotter or colder. We imagine the 

 rhythm of the universe is periodic, but until one 

 period is completed — and this the human race 

 cannot live to see — how can we tell, nay, even guess, 

 the nature of its periodicity ! The periodicity may 

 be complicated, is almost certainly more complicated 

 than that of a butterfly which goes through the 

 stages, egg, caterpillar, chrysalis, butterfly, and so 

 on, and what being could by the closest inspection 

 of, say, a millionth of any one of the sub-periods, egg, 

 caterpillar, chrysalis, or butterfly, foretell the other 

 sub-periods ! It is probably thus when we attempt 

 to explain the evolution of the stars. When Laplace 

 wrote his nebular hypothesis facts were few, the 

 laws of thermodynamics had not even been formu- 

 lated, and modern chemistry was in its infancy. 

 Hypotheses without facts are not uncommon ; the 

 Greek geniuses loved hypotheses, but seemed to dis- 



dain facts, and the effects of their examples are 

 buried deep in the fibres of our mentality. The 

 fundamental assumption of the nebular hypothesis 

 is that a nebula can condense, not only get more 

 dense, but even ultimately form liquids and solids of 

 various atomic weights. This assumption has no 

 foundation in nature, and is so improbable that it 

 should not be accepted without proof. Lockyer's 

 meteoric hypothesis started with a swarm of solid 

 bodies, meteorites, which by their collisions gave 

 rise to a nebula, which then followed the Laplacian 

 theory ; but the spectroscopic evidence on which it 

 rested has since been proved to be devoid of 

 foundation. 



Although many cosmological hypotheses have 

 been imagined, I wish to show that another can be 

 added to them ; its only merit is that it takes into 

 account the few facts of observation which are 

 available to-day. The hypothesis is compounded of 

 the planetesimal hypothesis of Chamberlin and 

 Moulton, and the radiation theory of Arrhenius, 

 with the addition of an explosive element suggested 

 by the mutations of uranium radium-helium. 



The primordial stuff out of which the universe is 

 made is in the form of meteors. Aggregations of 

 meteors are caused by collisions and gravitation. 

 These aggregations increase in size forming, firstly, 

 . cometary bodies ; secondly, planetary bodies ; 

 thirdly, sun-type bodies. Growth is continuous in 

 one direction in all these bodies, so that a cometary 

 body by the addition of more meteorites can pass 

 into a planetary body, and a planetary body similarly 

 into a sun-type body, but a sun-type body cannot 

 increase in size indefinitely, as a time comes when it 

 will disrupt with explosive force. A cometary body 

 is a loose aggregation of meteors. A planetary body 

 is a solid body in which the forces of solidification 

 and cohesion are at a maximum. A sun-type body 

 is a liquid body, of which the sun is a prototype. 

 The reverse process cannot take place; thus a sun- 

 type body cannot shed meteorites and so lose matter 

 that it becomes a planetary body, and so on. Under 

 certain circumstances, such as the near presence of 

 a large mass, a cometary aggregation can, however, 

 be dissipated, but this is an indirect effect which 

 does not concern us here. All three classes of 

 bodies can radiate substance in the form of 

 electrons, although at vastly different rates, so that 

 they can pass from the solid or liquid state to the 

 gaseous state, which is and will be called here the 

 stellar state, and from the gaseous or stellar state to 

 the final form, the nebulous state. The stellar state 

 is the first step in the degradation of atomic matter. 



It has to be considered how this hypothesis fits 



A paper Vead to the Science Congress, Lourenco Marques. 



369 



