161 



toals, then Phuick in the (luantuni hypothesis has in liis turn discovered a 

 wholly new method of scientific calculation, and in fact this hypothesis, already 

 so useful, is not a mere atomic theory of energy but in reality something wholly 

 new, because the quantum can assume any chosen value from zero upward 

 according to the motion of the atom concerned." The late Henri Poincar6 

 wrote concerning it: "The new conception is seductive from a certain stand- 

 point: for some time the tendency has been toward atomism. Matter ap- 

 pears to us as made up of indivisible atoms; electricity is no longer continu- 

 ous, not infinitely divisible, it resolves itself into equally charged electrons; 

 we have also now the magneton, the atom of magnetism. From this point 

 of view the quanta appear as atoms of energy."^ 



The physical assumptions which Planck makes may be summarized as 

 follows:* 



(1) A system of many linear Hertzian oscillators, having a coRynon 

 period of vibration and so spaced as not to exert direct influences upon one 

 another, are contained in a vacuum bounded by perfectly reflecting surfaces 

 and filled with stationary black radiation. 



(2) These oscillators onlj' absorb and emit energy in the form of electro- 

 dynamic wave radiation. 



(3) The vibration energy of an oscillator is given by the equation 



1 1 

 U = - Ivf- -f - L 



2 2 



fdfl = 

 — I , where f = electric moment of the oscillator, and K 



[dtj 

 and L are positive constants. 



(4) Emission only occiu-s when the vibration energy U is any whole 

 number of times the energy-element, the so-called "Elemcntnr-quanlum," 



1 /IC 

 E = hvo, where vo is the frequencv of the oscillator and is ecjual to — I — , 



2xA' L 



and h is a universal constant, the so-called "W irkungs-qiutniinn ," and is equal 



to 6.55 -i- 10"" erg-seconds. 



Whether the oscillator will actually absorb or emit energy at such times 



depends upon circumstances. If, however, emission occurs then the whole 



energy of vibration is emitted and the vibration ceases. Then through new 



absorption the energy again increases. Some writers on the "quanta theory" 



argue that the oscillators must absorb as well as emit energy in discrete 



amounts. It is claimed, for instance, that Einstein's formula for specific 



'Journ. de Phys. 2, Ser. ,5, pp. .5-34, 1912; ibid 2, Ser. n, pp. 347-360, 1912. 



«Ann. der Phys. 4, pp. 5.53-563, 1901; ibid 31, pp. 758-768, 1910; ibid 37, pp. 65-90, 1911. 



11—33213 



