NEW THEORIES OF THE EVOLUTION 

 OF STELLAR SYSTEMS 



By F. W. HENKEL, B.A., F.R.A.S. 



During the last few years the researches of Chamberlin, F. 

 R. Moulton and See on the evolution of our system have greatly 

 shaken the faith of astronomers in Laplace's well-known Nebular 

 Hypothesis. More than a century ago Laplace, who more 

 completely than any other had worked out the consequences 

 of Newton's theory of gravitation to the satisfactory explanation 

 of almost every known feature of the motions of the planets, 

 developed a hypothesis previously proposed by Swedenborg, 

 Wright and the great philosopher Kant. The Solar System 

 consists of a number of bodies arranged in an orderly manner, 

 all moving in nearly circular paths round the central body, 

 these paths being all nearly in the same plane and their motion 

 in the same direction, whilst there is a fairly regular progression 

 of distances from the sun (Bode's Law), and the bodies are either 

 spherical or spheroidal. These features are by no means a 

 necessary consequence of gravitation and seemed to imply an 

 original connection or common origin. Laplace supposed that 

 at one time the matter now forming the sun, earth and other 

 planets was in the form of an intensely hot gas, perhaps hotter 

 than the sun is now. This mass was of approximately spherical 

 form and rotated slowly on its own axis, the rotation becoming 

 swifter as the mass grew colder and contracted. In time rings 

 of matter would be left behind the main mass (not thrown off 

 as is sometimes stated) ; each of these rings would gradually 

 collect into a single globe, and thus the planets would be 

 formed. A planet thus formed continuing to revolve might 

 itself abandon rings in contracting ; these rings would form 

 into the satellites. The rings of Saturn were at one time 

 thought to be examples of this process, but we now know that 

 they are composed of swarms of meteorites rather than of 

 continuous substance. Plateau devised an experiment illus- 

 trating this formation of rings. He prepared a mixture of 



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