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exerts on a planet P, which absorbs all the received radiation, and 
which is at a distance A from the centre of the nebula. 
An element dr of the nebula emits in the direction OP a quantity 
of radiation given by: 
Se PPS cos w 
——_—_——— dt 
oe 
_ when u = absorption coefficient, & — distance from dr to planet, s = 
length of the path passed over by the radiation inside the nebula, 
S =the intensity of radiation, which we shall assume to be constant 
inside the nebula (see figure). 
Fig. 1. 
When dr is taken = a'*d« sin w dw dw, and 7, = radius of the 
planet, the radiation of the whole nebula on the planet is: 
= wnt { [ae dw dw sin Wcoswe-Hes. . . . (2) 
When we introduce p instead of w (see figure) through: 
A sinw = R sin p 
and when we take du = ds, (2) passes into: 
hr 2Rceose 2 
ar, SR? ¥ j 
= uJ dp | ds fo poos pe kPsdo . . … (3) 
0 0 
Integration yields‘): 
Kroes Sl 
A= = sk P-2.4 Pole-P 1 P- e-P]| 
— ue . (4) 
P=2u0k 
1) Compare: Borrtuineer, “Die Gravitationstheorie und die Bewegung des Mondes”’, 
Bayerische Akademie, 1912. 
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