144. ANNUAL REPORT SMITHSONIAN INSTITUTION, 1946 
Laplace, Kant, and Swedenborg; the collision hypotheses of Buffon 
and, much later, of Bickerton; the tidal-disruption theories of Cham- 
berlin and Moulton, Jeans, and Jeffreys; the grazing-impact hypo- 
thesis of Jeffreys; the double-star plus collision suggestion of Russell 
as developed by Lyttleton; the vague nebular-filament hypothesis of 
Nolke, and various internal-explosion theories, such as that considered 
by Ross Gunn. There are variations on some of these hypotheses, and 
some of them have been repaired by ad hoc assumptions and subhypoth- 
eses. Eventually one of them may be patched up into scientific re- 
spectability. Among the modern critics have been Luyten, Hill, Jeff- 
reys, and, most usefully, Russell, who has critically examined both 
the data and the theories.’ 
At present the general feeling seems to be that the earth probably 
came from a star, and that it is therefore the daughter of catastrophe. 
The mass is not large enough to make the precrustal existence 
clear or simple, but it must have been brief. Doctor Jeffreys has 
recently written: 
I think that the most serious difficulty of all catastrophic theories, affecting 
both Jeans’s theory and mine, and also Lyttleton’s further modification, is that 
the newly formed planets would need to be able to control not only the velocities 
of thermal agitation but alse those of general expansion due to the sudden 
relief of pressure.® 
A RETREAT INTO CHAOS 
From the foregoing summary it is clear that our hope of tracing 
an orderly progress in the origin and career of the earth is still de- 
ferred. An elaborate examination of the dynamical history of the 
various planets may be helpful in the search for an acceptable theory ; 
and possibly the contributions from geologists and seismologists con- 
cerning the inner structure of the earth may be suggestive. There is 
work of useful sort to be done on asteroids, comets, and meteors; and 
a searching of the stars and interstellar spaces of the solar neighbor- 
hood for giant planets that act like stars, and subdwarf stars that 
simulate planets. With the recent discovery of a neighboring star 
(mass unknown) that is about a million times fainter than the sun,? 
- we may be led in the direction of thinking of Jupiter, which has a 
mass one-thousandth the solar mass, as an extinct subdwarf companion 
of the sun. That concept would turn our cosmogonical speculation 
more in the direction of the dynamics of double stars with unequal 
components than in the present direction of collisional and catas- 
trophic phenomena. 
7 The solar system and its origin. The Macmillan Co., New York, 1935. 
® Nature, vol. 153, p. 140, 1944. 
® Van Biesbroeck, G., Harvard Announcement Card No. 678, January 26, 1944. 
