Evening star., 1932-02-14

?
Prof. T. C.. Chanrbcrlin of the Unirer-
sity of Chicago. one o the orIgindfors
of the planetesimal hypothesis, whtch
repIaced Laplace's theory and Which is
no,c attacked bv DR.. Cunn S suggestion.
cooled, rings of gas we're thrown off by its rota-
tion somewhat like the rings Of Saturn. These
rings were supposed to have condensed into the
planets forming the solar system
This idea of the nebular origin of the PLAN
etary system was proposed in l775 by the Ger
man philosopher, Kant Twenty years later
the great French mathematician, Laplace
(noted for his epigram that he had need
of God in his system OF celestial mechanlcs),
gave the nebular theory Its mathematical
form
Sir James Jeans, one Of the modern con-
testants in this arena. has now SHOWN that,
though Iaplaces nebular evolution Goes take
place in the heavens ii is on an incomparably
grander scale The great nebulae which can
be seen through powerful telescopes, thousands
of light-years away eFoIVe by very similar
process.
A SMALL mass of hot gas could not, how
i ever, break up IN lI4lS Way, SclehIStS Uc-
lieved till Jeans has also shown that
ring of gases could not under the force OF its
own gravitation condense into spherical PLAN
ct For these and other reasons the grand con-
ception of Laplace has been in the Waste
basket for the last 30 years.
Other scientists, however, have not been IDLE.
Two of these Drs T. c. Chamberlin and F.
r. Moulton of the University of Chicago, in
1905 propounded the theory which first replac-
ed the nebular theory-the ''planetesmal
hypothesis.
Accepting the idea that single star left to
itself could never have given birth to the
planets they were forced to assume that an
other celestial body have co-operated.
A MOTHER star, they believed, must have
n come close to the at some remote
time that by gravitational force it drew Jumps
and great mass of diffused gas and small par:
ticles out from the sun. The two stars swlAA
around each other once, like country dancers,
and never saw each other again.
Those stray wandering Jumps were smaller
than the present planets But as they whirled
collision, they gradually picked up more and
more matter. The planets had then reached
their present size and they moved In nearly
circular orbits.
Sir James Jeans and Dr. Harold Jeffreys of
Cambridge University, England, have made
further notifications of this collision theory.
They believe the newborn planets were liquid
and shot out from the parent practically full
grown.
IN Jeans theory the two stars did not actu-
] ally come into contact but passed so close
that great tides were raised in the sun. These
tides must have become powerful that the
gravitational pull of the no longer
able to hold them together. Liquid matter was
elected from the sun in a stream, which sub
sequently broke into pieces. These condensed
TO form the planets, as in Gums theory.
DIR. Jeffreys criticizes this theory, saying that
tidal and gravitationaI forces could not have
caused the rotations and revolutions that -.
tronomers observe in the planets.
Tidal disruption of the primitive sun would
leave 1t rotating as before and the planets
should now be rotating at the same speed as
the sum- he holds. Actually the sun rotates In
81 days. while Jupiter, a planet, turns around
once In 10 hours.
These difficulties can be avoided, says d.
Jeffreys II the two suns actually collided. 4
glancng blow from q heavier star would have
given our sun q jolt which could have produced
the desired rotation.
Explanations of the satellites of the planets
can be given on these theories, but on all the
earlier theories our moon remains extraordinary
and unexplained. With respect to the size a
its planet, the moon of the earth is one Of the
largest satellites in the solar system, yet the
earth is one Of the smallest planets. The moon
forms one-eightieth part of the weight d ~
earth