548 PROFESSOE J. H. POYNTING ON RADIATION IN THE SOLAR SYSTEM: 
temperature due to the solar radiation which it receives, but that it is still so large 
as to be attracted much more than it is repelled by the sun. Both attraction and 
repulsion are inversely as the square ot the distance, so that we shall have a central 
force which we may put as producing acceleration A/r-^, where A is constant. 
We know that at the distance of the earth, putting r = b, A/¥ = U-59 centim./sec.y 
sav 0-6 centim./sec." Then A = 0-66^. The force acting against the motion 
*/ ' 
produces retardation — 2Bw/U^/)a. 
If S is the solar constant at the distance h, its value at distance r is 
Putting 
iTra^Il = Sh^/r'^ 
B = (S/4) (6Vr^), 
then the acceleration in the line of motion is 
_ u ^ _Ts 
2UVa ’ ’ 
where T = Sb-/2'U'^pci, and .s is now written for the velocity w. 
The accelerations along and perpendicular to the radius vector give the equations 
.. A T.S cl) / 1 \ 
r — = 5- ^ ^ .Uh 
r" c(s 
1 d / y ]lS ) tlO / ‘7 \ 
V 76. 
From (2) we get 
d , TcW 
eft ~ ^ ’ 
whence 
rW = C - Td.(3), 
where C is the constant of integration. 
If d is 0 when ^ — 0, then C is the initial value of r'O. Further, as 0 increases 
V'd decreases and is 0 when 0 = C/T. Tliis gives a limit to the angle described. 
Equation (1) may be written 
r — rd- = — A/r~ — Tf/r*.(4). 
Putting u for )'~^ 
-■ = T$^ -{C- T(?) e 
= T (C - T») u- ~ - (C - T0)= IVoir (3) 
