rcular
sections, each bigger than the one inside it and separated from the
next by an area nearly as wide as the ring itself.

With such material in the heavens to guide him, La Place suggested
that the sun had once been an enormous fire mist scattered over an
area billions of miles in diameter. This gaseous material, by the
attraction of its particles for each other, began to condense and
contract. When the plug is pulled from a washbasin the particles of
water, in moving toward the center, in order to get out of the basin,
invariably set up a rotary motion. As the particles of this diffused
nebula began to gather together they, too, gave to the mass a rotary
movement. This grew more and more rapid, with greater contraction,
until the particles on the outer edge of the rotating mass had just so
much speed that the least bit more would make them tend to fly off as
mud would fly from a revolving wheel. When this point was reached
there was a balance of forces which made the outermost portion remain
as a ring while the rest contracted away from it, leaving it behind.

It was La Place's idea that this process had repeated itself, and ring
after ring had been left behind. Finally the sun condensed and grew
into a ball, occupying the center of the system. At varying distances
from it were to be found either rings or planets which had been formed
out of such rings. For La Place suggested that in a ring like this
the material could not be quite evenly distributed. While every
particle in the ring kept revolving around the sun, those in front of
the densest part were slowly held back by the attraction of the
thicker portion, while those behind it in rotation had their speed
hastened until finally all the material in the ring had collected at
one spot and a new planet was born. La Place believed that these
planets formed their moons in exactly the same way, and that Saturn
was simply a planet not all of whose moons had yet been formed. He
believed that this happy accident served to tell us how the universe
had been created.

Of course, so detailed a theory concerning anything of which we know
so little has always had much ridicule thrown upon it, and yet no
truly competing theory has been proposed until very recent times.

Within a few years a Planetesimal Theory has been announced, and is
gaining considerable prominence, although it is too early yet to say
whether it will supersede La Place's idea. In this theory, also, the