these remoter suns there are many aggregations of
matter which are not consolidated as are the spheres of our own solar
system, but remain in the gaseous state, receiving the name of nebulae.

Along with the growth of observational astronomy which has taken place
since the discoveries of Galileo, there has been developed a view
concerning the physical history of the stellar world, known as the
nebular hypothesis, which, though not yet fully proved, is believed by
most astronomers and physicists to give us a tolerably correct notion
as to the way in which the heavenly spheres were formed from an
earlier condition of matter. This majestic conception was first
advanced, in modern times at least, by the German philosopher Immanuel
Kant. It was developed by the French astronomer Laplace, and is often
known by his name. The essence of this view rests upon the fact
previously noted that in the realm of the fixed stars there are many
faintly shining aggregations of matter which are evidently not solid
after the manner of the bodies in our solar system, but are in the
state where their substances are in the condition of dustlike
particles, as are the bits of carbon in flame or the elements which
compose the atmosphere. The view held by Laplace was to the effect
that not only our own solar system, but the centres of all the other
similar systems, the fixed stars, were originally in this gaseous
state, the material being disseminated throughout all parts of the
heavenly realm, or at least in that portion of the universe of which
we are permitted to know something. In this ancient state of matter we
have to suppose that the particles of it were more separated from each
other than are the atoms of the atmospheric gases in the most perfect
vacuum which we can produce with the air-pump. Still we have to
suppose that each of these particles attract the other in the
gravitative way, as in the present state of the universe they
inevitably do.

Under the influence of the gravitative attraction the materials of
this realm of vapour inevitably tended to fall in toward the centre.
If the process had been perfectly simple, the result would have been
the formation of one vast mass, including all the matter which was in
the original body. In some way, no one has yet been able to make a
reasonable suggestion of just how, there were developed in the
process of concentration a great many separate centres of aggregation,
each of which became the