24 LIFE: ITS NATURE AND ORIGIN 



1.6603 x 10" 24 gram. The unit of electric charge used is the positive 

 charge of the proton, which is equal in magnitude but opposite in sign 

 to the charge on the electron, and is often called the electronic charge; 

 its value is 1.60xl0- 19 coulomb. The energy unit used in nuclear 

 physics is the electron-volt, denned as equal to the kinetic energy which 

 a particle carrying one electronic charge will acquire in falling freely 

 through a potential drop of one volt. Since this is so tiny, the million 

 electron volt unit (mev) is commonly used. 



Returning now to the experimental results, 0.0185 mass unit is 

 3.07 x 10- 26 gram, 17 mev is 27.2 x 10- 6 erg, and c (the velocity of light) 

 is 3xl0 10 cm per second. On substituting these values in Einstein's 

 equation, E = mc 2 , we have 



27.2xl0- c erg = 27.6xl0- 6 erg 

 which is quite a good approximation to the equality of both sides. 



Source of the Sun's Radiant Energy 



According to C. G. Abbott, the energy received by the earth 

 from the sun is about 1.7 horsepower per square yard (1.47 kw 

 per square mile). This indicates an emission by the sun's surface 

 of 7.88 X 10 4 horsepower per square yard (6.79 X 10 4 kw per square 

 meter), which is heat enough to melt 39.6 feet of ice or to vaporize 

 5.92 feet of water per minute. Together, all the planets receive 

 less than 1/1 20th of one-millionth part of this tremendous energy, 

 which the sun has been pouring out for at least several billion 

 years. Apart from the fact that solar temperatures enormously 

 exceed those of any known chemical reaction, a sphere of coal the 

 size of the sun, burning in pure oxygen, would be entirely com- 

 sumed in about 6,000 years. The notion that meteoric matter, 

 falling into the sun, is a material factor in maintaining its heat 

 has long ago been dismissed, as has also the notion of Helmholtz 

 that solar contraction can account for the maintenance of solar 

 heat. 



The discovery of radioactivity, however, opened the door to new 

 vistas. Thus R. A. Sampson 14 stated: ". . . if the sources of energy 

 within the atom can be drawn upon, there is here an incalculable 

 source of heat which takes the cogency out of any calculation 

 respecting the sources of maintaining the sun's radiation. An 

 equivalent statement of the same conclusion may be put thus. 

 Supposing a gaseous nebula is destined to condense into a sun: the 

 elementary matter of which it is composed will develop in the 

 process into our known terrestrial and solar elements, parting 

 with energy as it does so." 



