THE NEBULAR HYPOTHESIS 187 



is the cold of space 200 or more Centigrade below zero, that they 

 bear within, proof of their cosmic habitat. 



I ask, How many such meteoritic impacts as this of 

 Dhurmsala at 200 below zero would be required to make 

 up a sun as hot as ours ? or how many million years 

 would be required for them to "cool" up to the molten 

 condition of the major planets? 



Here is another piece of testimony from the recent 

 work of Professor T. C. Chamberlin, of the University of 

 Chicago, The Origin of the Earth, (p. 163) : 



Meteorites, even after they have plunged through the whole 

 atmosphere and into the earth, are said sometimes to retain a 

 very low temperature within. They are reported even to freeze 

 the earth in which they imbed themselves. At any rate, the low 

 temperatures brought in from space must be set over against 

 the heat of atmospheric friction in the ledger of temperature ef- 

 fects. Very significant, in this respect, is the almost incredible 

 existence of a small class of meteorites largely formed of volatile 

 and combustible hydrcarbons. These have reached the earth 

 without either complete vaporization or combustion. 



The shortcomings of the collisional theory became 

 early apparent, so that, in the year 1854, Helmholtz was 

 led to propose a new explanation of the solar heat. Dis- 

 cussing this theory Doctor Abbot says (The Sun, p. 277) : 



Helmholtz pointed out that the shrinking together of the sun 

 converts potential energy of position finally into heat. Several 

 authors have made computations of the quantity of energy which 

 would be available from this source. Their results have generally 

 been based on the assumption that the sun was originally a nebula 

 filling a sphere whose diameter was the orbit of Neptune. It ap- 

 pears that the condensation of such a nebula having the mass of 

 the sun would have furnished thus far about 25,000,000 times as 

 much energy as the sun now loses each year. 



According to Helmholtz's view, a contraction of about 250 

 feet per year in the sun's diameter would suffice to sustain the 

 present solar radiation. At this rate it would require about 

 10,000 years to reduce the apparent diameter of the sun by one 

 second of arc, so that, so far as telescopic observation is con- 

 cerned, the contraction theory is tenable, for a change of i/io 

 second in the solar diameter is unrecognizable. From calcula- 

 tions of Newcomb the sun will require to have shrunk to one- 

 half its present size if it maintains its present rate or radiation for 

 about 7,000,000 years longer. 



