This century has been conspicuous above all centuries for new things.
Man has grown into new relations with both nature and thought. He has
interpreted nearly everything into new phraseology and new forms of
belief. The scientific world has been revolutionized. Nothing remains
in its old expression. Chemistry has been phrased anew. The laws of
heat, light and electricity have been either revised or discovered
wholly out of the unknown. The concept of universal nature has been so
translated and reborn that a philosopher coming again out of the
eighteenth century would fail to understand the thought and speech of
even the common man.
In no other particular has the change been more marked than with
respect to the general theory of the planetary and stellar worlds. A
New Astronomy has come and taken the place of the old. The very
rudiments of the science have to be learned as it were in a new
language, and under the laws and theories of a new philosophy. Nature
is considered from other points of view, and the general course of
nature is conceived in a manner wholly different from the beliefs of
the past.
In a preceding study we have explained the general notion of planetary
formation according to the views of the last century. The New
Astronomy presents another theory. Beginning with virtually the same
notion of the original condition of our world and sun cluster, the new
view departs widely as to the processes by which the planets were
formed, and extends much further with respect to the first condition
and ultimate destiny of our earth. The New Astronomy, like the old,
begins with a nebular hypothesis. It imagines the matter now composing
the solar group to have been originally dispersed through the space
occupied by our system, and to have been in a state of attenuation
under the influence of high heat. Out of this condition of diffusion
the solar system has been evolved. The idea is a creation by the
process of evolution; it is evolution applied to the planets. More
particularly, the hypothesis is that the worlds of our planetary
system grew into their present state through a series of stages and
slow developments extending over æons of time.
This is the notion of world-growth substituted for that of
world-production en masse by the action of centrifugal force and
discharge from the solar equator. The New Astronomy proposes in this
respect two points of remarkable difference from the view formerly
entertained. The first relates to the fixing of the planetary orbits,
and the other to the process by which the planets have reached their
present mass and character. The old theory would place a given world
in its pathway around the sun by a spiral flinging off from the
central body, and would allow that the aggregate mass of the globe so
produced was fixed once for all at the beginning. The new theory
supposes that a given planetary orbit, as for instance that of the
earth, was marked in the nebula of our system before the system
existed--that is, that our orbit had its place in the beginning just
as it has now; that the orbit was not determined by solar revolution
and centrifugal action, but that it was mathematically existent in the
nebular sheet out of which the solar system was produced.
Other lines existed in the same sheet of matter. One of these lines or
pathways was destined for the orbit of Mercury; another for the orbit
of Venus. One was for the pathway of Mars; another for the belt of
the asteroids; another for Jupiter; another for Saturn, and still two
others, far off on the rim, for Uranus and Neptune. The theory
continues that such are the laws of matter that these orbital lines
_must_ exist in a disc of fire mist such as that out of which our
solar universe has been produced. The New Astronomy holds firmly to
the notion that the orbits of the planets are as much a part of the
system as the planets themselves, and that both orbit and planet exist
in virtue of the deep-down mathematical formulæ on which the whole
material universe is constructed.
Secondly, the New Astronomy differs from the old by a whole horizon in
the notion of world-production. About the middle of the century the
theory began to be advanced that the worlds _grew_ by accretion of
matter; that they grew in the very paths which they now occupy; that
they began to be with a small aggregation of matter rushing together
in the line or orbit which the coming planet was to pursue. The
planetary matter was already revolving in this orbit and in the
surrounding spaces. It was already floating along in a nebulous
superheated form capable of condensation by the loss of heat, but in
particular capable of growth and development by the fall of
surrounding matter upon the forming globe. We must remember that in
the primordial state the elements of a planet, as for instance our
earth, were mixed together and held in a state of tenuity ranging all
the way from solid to highly vaporized forms, and that these elements
subsequently and by slow adjustment got themselves into something
approximating their present state.
The New Astronomy contemplates a period when each of the planets was a
germinal nucleus of matter around which other matter was precipitated,
thus producing a kind of world-growth or accretion. Thus, for
instance, our earth may be considered at a time when its entire mass
would not, according to our measurement, have weighed a hundred
pounds! It consisted of a nucleus around which extended, through a
great space, a mass of attenuated planetary matter. The nucleus once
formed the matter adjacent would precipitate itself by gravitation
upon the surface of the incipient world. The precipitation would
proceed as heat was given off into space. It was virtually a process
of condensation; but the result appeared like growth.
To the senses a planet would seem to be forming itself by accretion;
and so, indeed, in one sense it was; for the mass constantly
increased. As the nucleus sped on in the prescribed pathway, it drew
to itself the surrounding matter, leaving behind it an open channel.
The orbit was thus cleared of the matter, which was at first merely
nebular, and afterward both nebular and fragmentary. The growth at the
first was rapid. With each revolution a larger band of space was swept
clear of its material. With each passage of the forming globe the
matter from the adjacent spaces would rush down upon its surface, and
as the mass of the planet increased the process would be stimulated;
for gravitation is proportional to the mass. At length a great tubular
space would be formed, having the orbit of the earth for its centre,
and in this space the matter was all swept up. The tube enlarged with
each revolution, until an open way was cut through the nebular disc,
and then from the one side toward Venus and from the other side toward
Mars the space widened and widened, until the globe took approximately
by growth its present mass of matter. The nebulous material was drawn
out of the inter-planetary space where it was floating, and the shower
of star dust on the surface of the earth became thinner and less
frequent. In some parts of the orbit bands or patches of this material
existed, and the earth in passing through such hands drew down upon
itself the flying fragments of such matter as it continues to do to
the present day. What are meteoric displays but the residue of the
primordial showers by which the world was formed?
All this work, according to the New Astronomy, took place while our
globe was still in a superheated condition. The mass of it had not yet
settled into permanent form. The water had not yet become water; it
was steam. The metals had not yet become metals; they were rather the
vapor of metals. At length they were the liquids of metals, and at
last the solids. So, also, the rocks were transformed from the
vaporous through the liquid into the solid form--all this while the
globe was in process of condensation. It grew smaller in mathematical
measurements at the same time that it grew heavier by the accretion of
matter. At last the surface was formed, and in time that surface was
sufficiently cooled to allow the vapors around it to condense into
seas and oceans and rivers. There were ages of superficial
softness--vast epochs of mud--in which the living beings that had now
appeared wallowed and sprawled.
We cannot trace the world-growth through all its stages but can only
indicate them as it were in a sketch. The more important thing to be
noted is the relation of our planet in process of formation to the
great fact called life. Here the New Astronomy comes in again to
indicate, theoretically at least, the philosophy of planetary
evolution. Each planet seems to pass through a vast almost
inconceivable period in which its condition renders life on its
surface or in its structure impossible. Heat is at once the favoring
and the prohibitory condition of life. Without heat life cannot exist;
with too great heat life cannot exist. With an intermediate and
moderate degree of heat many forms of animate and inanimate existence
may be promoted.
These facts tend to show that every world has in its career an
intermediate period which may be called the epoch of life. Before the
epoch of life begins there is in the given world no such form of
existence. There is matter only. Then at a certain stage the epoch of
life begins. The epoch of life continues for a vast indeterminate
period. No doubt in some of the worlds an epoch of life has been
provided ten times as great, possibly a thousand times as great, as in
other planets. After the epoch of life begins only certain forms of
existence are for a while possible. Then other and higher forms
succeed them, and then still higher. Thus the process continues until
the highest--that is, the conscious and moral form of existence
becomes possible, and that highest, that conscious, that moral form of
being is ourselves.
This is not all. The epoch of life seems to be terminable at the
further extreme by a planetary condition in which life is no longer
possible. The New Astronomy indicates the coming of a condition in all
the worlds when life must disappear therefrom and be succeeded by a
lifeless state of worldhood. This may be called the epoch of
death--that is, of world-death. It seems to be almost established by
investigation and right reason that worlds die. They reach a stage in
which they are lifeless. They cool down until the waters and gases
that are on the surface and above the surface recede more and more
into the surface and then into the interior, until they wholly
disappear. Cold takes the throne of nature. Universal aridity
supervenes, and all forms of vegetable and animate existence go away
to return no more. They dwindle and expire. The conditions that have
come are virtually conditions of death.
Whether the universe contains within itself, under the Almighty
supervision, certain arrangements and laws by which the dead world can
be again cast into the crucible and regenerated by liberation through
the action of heat into its primordial state once more and go the same
tremendous round of planet life, we know not. The conception of such a
process, even the dream or vague possibility of it, is sufficiently
sublime and fills the mind with a great delight in contemplating the
possible cycles through which the material universe is passing.
At any rate, we may contemplate the three great stages of world-life
with which we are already acquainted--that is, the birth stage, the
epoch of life and the epoch of death. There is a birth, as also a life
and a death of planets. Richard A. Proctor, of great fame, on one of
his last tours of instructive lecturing among our people, had for his
subject the "Birth and Death of Worlds." The theme was not dissimilar
to that which has been here presented in outline. The birth, the life
and the death of worlds! Such is a summary of that almost infinite
history through which our earth is passing--the history which the
globe is _making_ on its way from its nebulous to its final state.
Such, if we mistake not, is the story epitomized--the life history in
brief--of all the worlds of space. They have each in its order and
kind, an epoch of the beginning, then an epoch of growth and
evolution, then an epoch of life--toward which all the preceding
planet history seems to tend--and finally an epoch of death which
must, in the course of infinite time, swallow from sight each planet
in its turn, or at least reduce each from that condition in which it
is an arena of animated existence into that state where it is a
frozen and desert clod, still following its wonted path through space,
still shining with a cold but cheerful face, _like our moon_, upon the
silent abysses of the universe.