48 ILLINOIS ACADEMY OF SCIENCE 
EARTH GENESIS 
T. C. CHAMBERLIN, UNIVERSITY OF CHICAGO 
(Special address, Complimentary to the People of Gales- 
burg. ) 
To those who feel an interest in the evolution of the earth, 
it is of first moment to learn how the planet was born and 
what conditions controlled its growth. The other planets of 
our system no doubt had a birth of like nature and these, as 
well as the earth, bear traits that serve as signs of the family 
lineage. It is not clear that the sun was born at the same 
time, or in just the same way. There is no doubt that the 
sun and the planets are close akin, but this does not make it 
sure that they were participants in a common birth. We shall 
present evidence that the planets sprang from the sun, not 
at his birth, but later in the course of his history. The sa- 
tellites might easily seem to be the offspring of the planets 
and this was the common view in the last century, but there 
are signs that planets and satellites had a common birth and 
that the satellites escaped being little planets only because 
their birth-places fell within the spheres of control of their 
larger sisters to whom they were forced to dance attendance 
as a first duty, and respond to the common call of the sun 
incidentally. If these relations are true, we may search the 
planets, planetoids and satellites for signs of the later family 
history, while we look to the sun for signs of their parentage 
and of the earlier history. 
But are these real kinships? Let us look to the evidence. 
If the planets were separated by centrifugal action from 
a nebula of which the sun is regarded as the residual mass 
—the view that was foremost during the last century—the 
planets should revolve in paths that lie in the plane of the 
sun’s equator. But the plane of the earth’s orbit is inclined 
7° 15’ to it and the planes of the orbits of the other planets 
and planetoids diverge at other angles. These angles may 
not seem to imply a very wide departure from the theoretical 
requirement, but when the immensity of momenta of these 
bodies is considered the divergence is really serious. 
But there are much more formidable difficulties. If the 
planets were separated from the parent nebula at successive 
