RADIANT ENERGY 403 



their two outer electrons and thus possess a positive charge of 

 2e(2 X 4.77 X lO"^" e.s.u.). They are very easily absorbed, 

 being completely stopped by 0.1 mm. of aluminum or a few 

 centimeters of air. 



Beta particles are free electrons and therefore carry a negative 

 charge. They move at high speed, being almost as rapid as light 

 rays, and are more penetrating than alpha particles passing 

 through a millimeter of aluminum (or a meter of air). They are 

 identical with cathode rays, differing only in velocity. 



Gamma rays are regarded as pulses in the ether of very short 

 wave length (about 10"^ cm.), just as are X rays and all other 

 light rays (Fig. 166). Gamma rays, X rays, and ultraviolet rays 

 may be grouped together because of similar characteristics. 

 Gamma rays are exceedingly penetrating, those from radium 

 producing measurable effects through a thickness of 20 or 30 cm. 

 of iron. Both beta and gamma radiation is given off not only 

 by the heavy radioactive elements but also by Ughter elements 

 such as potassium, which suggests that potassium is transmuted 

 into calcium. 



Alpha, beta, and gamma radiation is given off by radium and 

 causes it to degenerate ultimately into lead. (It requires about 

 20,000 years for the degeneration of radium and more than 

 4,000,000,000 years for uranium to become converted into lead.) 

 There are 88 positive charges (balanced by negative planetary 

 electrons) in a radium atom and 92 in a uranium atom. If but 

 six of these are to be lost over so great a period of time in order 

 to produce an atom of lead (atomic number 82), then the number 

 likely to come from one atom in a given interval of time must be 

 very, very small indeed. That we observe a constant stream of 

 electrons coming from a piece of radium is due to the fact that 

 the piece contains billions upon billions of atoms. (10^^ or a 

 thousand milUon million atoms, are in 4 X lO"'', or four ten- 

 miUionths of a gram of uranium.) 



There is an interesting feature of radium radiation which is in 

 keeping with the uncertainty principle of Heisenberg. The rate 

 at which an infinitely small amount of radium will radiate is not 

 known with certainty; that is to say, if the amount is reduced to 

 one atom, the frequency with which it will give off a particle is 

 not predictable. Furthermore, the event takes place within the 

 minute universe of the atom with as much Ukelihood as that our 



