THE NEBULAR HYPOTHESIS: ITS BASIS AND ITS DIFFICULTIES.
"There sinks the nebulous star we call the Sun,
If that hypothesis of theirs be sound."--Tennyson.
While the nebular theory of Laplace is now the generally accepted
scientific hypothesis of the formation of our solar system and of
all solar systems, it finds its strongest support in the mode in
which it seeks to account for the heat and light of the sun,--that
is, that the central orb, gradually condensing down from an original
volume as large as the orbit of Neptune, at least, after disengaging
the planetary rings, continued to condense to its present volume,
and still so continues, the molecular motions arrested by condensation
under gravity reappearing in the form of the energy of light and heat,
and that this process of degradation will continue until, finally,
the sun becomes a solid inert mass, incapable by further condensation
of exciting the ethereal undulations in space which constitute heat and
light, when the whole process will finally cease, the sun will die out,
the planets continue to rotate in darkness, and the whole machinery be
left running through an eternal night, like a vast mill in the hands
of a negligent watchman (or rather no watchman at all), left to run
itself alone, dark, empty, lifeless, and deserted, through the long and
silent watches of the night. While the source and mode of solar energy
set forth in this work are to be as readily accounted for if we accept
as valid Laplace's nebular hypothesis as by any other theory, yet
such basis is not essential for its support; for while the planetary
rotations and the central sun are the necessary consequence, according
to Laplace's hypothesis, of their mode of formation,--are, in fact,
just what we actually find them to be under any hypothesis,--electrical
generation and transformation will proceed just the same whether the
planets and sun were formed originally in one mode or in another. But,
since this generally accepted hypothesis accounts for the light and
heat of the sun, to a certain extent at least, and for a certain
relatively brief period, while no other hypothesis has been able to
sufficiently account for it at all, and while this hypothesis also
finds both support and contradiction in many observed phenomena of
our solar system, it may well occur that this hypothesis itself,
based upon the necessity of accounting for the sun's light and heat,
and which latter afford it its strongest basis of support, may,
if the basis upon which the theory rests be found to be otherwise
explicable, still remain as an end, while originally presented only
as a means, and thus be held as an obstacle to the acceptance of the
widely different interpretation of known facts herein presented, in
the absence of any other hypothesis capable of explaining the same
facts in accordance with this presentation of planetary electrical
generation and the solar transformation of this energy into light
and heat. Herbert Spencer mentions an instance of such perversion of
means into an end as occurring during the agitation for the repeal
of the corn laws in England, which extended over many years, during
which organized efforts were made to influence Parliament. A permanent
commission was established, with official head-quarters permanently
located in London, with clerks, secretaries, higher officers, and
all the paraphernalia of a first-class establishment. The purpose of
this institution was to act in behalf of the popular interests upon
Parliament by every available means to secure this great reform. After
years of effort, he says, a clerk one day rushed, breathless, into the
office from the House of Commons and shouted, in accents of despair,
"We are ruined; the bill has passed!"
The nebular hypothesis, while generally accepted in lieu of a better
one, has no actual primary basis beyond that of mere assumption. Of
it Professor Ball says, "The nebular theory ... seems, from the
nature of the case, to be almost incapable of receiving any direct
testimony." We have already quoted from Professor Newcomb that it
must be accepted, with all its difficulties, until a different and
sufficient explanation of solar energy shall be presented. As set
forth in Appleton's Cyclopædia, the theory is as follows: "Assuming,
for the sake of the argument, a rare, homogeneous, nebulous matter,
widely diffused through space, the following successive changes will,
on physical principles, take place in it: 1, mutual gravitation of
its atoms; 2, atomic repulsion; 3, evolution of heat by overcoming
this repulsion; 4, molecular combination at a certain stage of
condensation; followed by, 5, sudden and great disengagement of heat;
6, lowering of temperature by radiation and consequent precipitation
of binary atoms, aggregating into irregular flocculi and floating in
the rarer medium, just as water when precipitated from air collects
into clouds; 7, each flocculus will move towards the common center of
gravity of all; but, being an irregular mass in a resisting medium,
this motion will be out of the rectilinear,--that is to say, not
directly towards the common center of gravity, but towards one or
the other side of it,--and thus, 8, a spiral movement will ensue,
which will be communicated to the rarer medium through which the
flocculus is moving; and, 9, a preponderating momentum and rotation of
the whole mass in some one direction, converging in spirals towards
the common center of gravity. Certain subordinate actions are to
be noticed also. Mutual attraction will tend to produce groups of
flocculi concentrating around local centers of gravity and acquiring
a subordinate vortical movement. These conclusions are shown to be in
entire harmony with the observed phenomena. In this genetic process,
when the precipitated matter is aggregating into flocculi, there will
be found here and there detached portions, like shreds of cloud in a
summer sky, which will not coalesce with the larger internal masses,
but will slowly follow without overtaking them. These fragments will
assume characteristics of motion strikingly correspondent to those of
the comets, whose physical constitution and distribution are seen to
be completely accordant with the hypothesis." During this process,
it is further stated, successive rings of nebulous matter will be
thrown off and left behind, which are supposed to have coalesced
into planets and their satellites, and the motion of rotation will
become more and more rapid as condensation proceeds, until, finally,
the last planet, Mercury, will be left behind in annular form,
and the sun will then become the central orb of all the planets,
and condensation afterwards will proceed without further delivery of
planetary rings. Professor Ball says, "If we go sufficiently far back,
we seem to come to a time when the sun, in a more or less completely
gaseous state, filled up the surrounding space out to the orbit of
Mercury, or, earlier still, out to the orbit of the remotest planet."
There is nothing in the actively developing nebula illustrated on
the following page which shows the slightest analogy, either in
structure or the forces at work, to what is demanded by the nebular
hypothesis. On the contrary, these radiating, spiral convolutions,
springing from a center and extended, with interstratified dark spaces,
out to the periphery, are entirely incompatible with that theory. There
have not, so far, been observed in all the heavens any gaseous
nebulæ which lend the slightest support to the nebular hypothesis. We
should expect to find, if it were true, that many of the nucleated
planetary nebulæ show exterior concentric rings of luminous matter,
clearly defined, two, three, or a dozen in number, left behind by the
contracting volume of the nebula, and coalescing into planets, and,
within, the glowing disk from which new external rings are about to be
left as a residuum. On the contrary, these nebulæ gradually fade away
towards their margins, and imperceptibly disappear in the blackness
of space. If they terminated abruptly, we might suppose that here,
at least, was the orbit of a newly forming planet, but the regular
and delicate gradation of luminosity from maximum to zero shows that
no such sudden breaking off has occurred. In all these nebulæ we find
every definitely marked structure to exhibit the operation of combined
forces of gravity and internal repulsion nearly equally balanced,
but each acting independently of the other. These phenomena are as
universal as the forces of cohesion and repellent polarity in the
"attraction particles" of cell-life which determine the segmentation,
growth, and development of the living organism. We find here the
primal modification and differentiation of material structure under
the stress of directly opposite and interacting primitive forces,
and it is doubtless the same whether in a cell or a system. It is
not a residuum, but the vis a tergo.
It is well known that there are many and great difficulties involved
in the nebular hypothesis. As for the genesis of comets, it will be
at once seen that the theory will only account for such comets as
never venture much beyond the orbit of Neptune, as well as those which
have an orbital plane nearly coincident with that of the planets. But
most comets come from illimitable space, far, far beyond Neptune's
circle and at all angles to the plane of the planetary orbits; and we
have already seen that a disk of space of the diameter of Neptune's
orbit and half as thick (see Proctor's "Familiar Essays") would,
to contain all the matter of our solar system equally distributed,
have a density of only one four-hundred-thousandth that of hydrogen
gas at atmospheric pressure,--that is to say, such a volume of the
lightest substance we know of would make four hundred thousand solar
systems like our own. This author inquires if such a mass could,
under any circumstances, rotate as a whole, and adds, "Has it ever
occurred, I often wonder, to those who glibly quote the nebular theory
as originally propounded, to inquire how far some of the processes
suggested by Laplace are in accordance with the now well-known laws of
physics?" But the great primal difficulty is in the first assumption
of the theory, which is not only entirely gratuitous, but physically
impossible. It is that this great plasma of nebulous material--in
the case of our own solar system not less than six thousand million
miles in diameter--should have in someway become aggregated into
a homogeneous mass of the requisite tenuity, complete and perfect,
and ready for the succeeding stages of the process, in which, however,
the law of gravity has hitherto had no active operation whatever; for,
if gravitation existed and operated therein, such homogeneous mass
could never have been formed, nor ever existed even if formed. The
very forces which alone could have brought this vast mass together
must have been the identical forces which afterwards broke it up into
the sun and planets, and the operation of the same force must have
prevented its original formation at all. According to the theory, it
was like a horse-race, in which all the participants stood silent and
motionless until the judge cried, "Go!" But the judge was the great
creative force itself, and if the fiat reached to this extent, the
same power could just as readily--nay, far more readily--have shot the
sun and planets forth into rotation, as children scatter dough-balls,
instead of holding in abeyance the control of universal law so as to
(as a humorous writer speaks of the operations of a child in his
investigation of a watch) "see the wheels go round." This is not
nature's plan, so far as human knowledge goes. Of course these masses
gathering to this great nebulous center, if acted upon by gravitation,
would have at once condensed around the center as a nucleus, and
if rotation ever commenced, it must have commenced then, millions
of years, doubtless, before the outlying masses had even got within
hailing distance. When masses of people assemble at a camp-meeting,
the first comers take the best places, and the late arrivals have to
circulate around in the woods; they do not all gather in a circle
and then make a grand rush. That would be fair, perhaps, but it is
not nature. And this, unquestionably, is how, if ever formed at all,
these nebulæ must have formed into systems.
The fact that the orbital planes of very many of these asteroids are
greatly inclined to the common planetary plane, and still more greatly
inclined to one another, points almost unerringly to the existence
during their stage of formation of some powerful force either of
internal repulsion or external attraction. That no sufficiently large
body could have been present to exercise such attraction so far outside
the general planetary plane is self-evident, and if there had been
such source of attraction, while the orbital planes of the asteroids
might have been deflected from the common plane, they could not have
been forced apart so as to differ largely among themselves. Certainly
nothing pertaining to the nebular hypothesis could have produced any
such effects under any conceivable circumstances, and especially at
so late a period of its progress, after all the principal planets had
been completed. The only alternative is self-repulsion, and this could
only have been due to the causes and their mode of operation already
described in this work. In a modified degree these planes exhibit the
same irregular orbital deflections as are so conspicuously visible in
the orbits of comets, and they must have been unquestionably produced
in the same manner. The barren bands or stripes in the area occupied by
these asteroids, like the dark or vacant rings of the planet Saturn,
may have been largely affected by the perturbing attraction of the
neighboring planet Jupiter; but certainly no influence of that great
planet (himself in the common planetary plane) could have operated
to cast these forming planetoids into planes of diverse inclinations
among themselves or to that of his own. On the contrary, his whole
force must have been exerted to bring them into the closest harmony
with his own orbital movements.
Omitting discussion of the technical difficulties in the application
of the nebular theory to demonstrated facts, which may be found in
the books, we may again repeat that this theory is not essential to
account for the heat of the sun, which finds its real source elsewhere,
while, nevertheless, the theory in itself is not incompatible with
the views which we have endeavored to present and demonstrate. Certain
phenomena, however, have been considered in prior quotations in this
work which may aid us to roughly indicate the successive processes by
which the evolution of solar systems and galaxies may be explained on
another basis which requires no violent assumptions to be made and no
suspension of any of nature's universal laws. The same operations which
we see around us at the present time in our own system, if extended to
the dimensions of a nebular aggregation, would probably present the
same phenomena as those we find partially disclosed in the gaseous
nebulæ, particularly the spiral, and these would naturally determine
the final production of solar systems such as our own. The gaseous
nebulæ, not spiral, and the mixed nebulæ also, would fall into their
appropriate categories in the same general plan, and a consistent
mode of formation would be presented from the beginning to the end
of the different processes.
It should be observed that the spiral required by Laplace's nebular
theory is essentially a centripetal spiral. The spiral nebulæ we see in
the heavens, however, are centrifugal spirals. This is clearly shown
in Plates XV., XII., and the frontispiece of Nichol's "Architecture
of the Heavens," as well as in Plates XIII. and XIV. Plate XV.--the
open spiral--is directly contradictory of any phenomena which
could occur in accordance with the nebular theory of Laplace. The
frontispiece shows the only form which such a nebula could assume
at any stage of its career,--that is, a close spiral with nearly
circular convolutions. But while this particular form is not only in
entire accordance with the hypothesis which we are about to suggest,
being in fact one of the later and necessary stages in its progress,
any such spiral as that shown in Plate XV. is utterly out of the
question in the application of the nebular theory of Laplace or in
any of the more recent modifications thereof.
The only hypothesis by which the various phenomena can be adequately
explained must almost certainly be based upon the combined action of
gravitation and electrospheric repulsion. We find in the corona of
our own sun such phenomena manifested in the most striking degree,
even in a completed system, and we can well understand that during
the early stages of systemic development such phenomena would vastly
transcend anything which we could now hope to observe around our
own sun. We see this repulsion still more highly developed in the
formation of the tails of comets. While these coronal rays are not
visible to a distance of more, perhaps, than five million miles
from the sun's disk, we have seen that the tail of Newton's comet
was shot forth to a distance of ninety million miles in a few days,
as it were in a moment, by the tremendous electrical repulsion of the
solar electrosphere, and that this enormous tail, which, if composed
of hydrogen gas alone (it was, of course, enormously more attenuated),
would have contained a mass much more than equal to the weight of the
sun, was swung around over an arc of one hundred and eighty degrees,
giving a radial sweep of the tail over a distance of two hundred
and eighty millions of miles in less than four days. And the tails
of many other comets have largely transcended in dimensions that of
Newton, above cited. We have learned much of the laws which regulate
the development of storms, cyclones, whirlwinds, water-spouts,
and other vortical phenomena in the atmosphere of our own earth,
and can readily apply these principles to phenomena of vastly greater
magnitude. We know that the matter of comets' tails is self-repulsive,
as shown in multiple tails, as well as that it is repelled by an
adjacent similarly electrified electrosphere,--that of the sun, for
example,--as with pith-balls in the familiar class-room experiments;
so that we can gather a very fair and complete idea of the processes
of nature when dealing with such phenomena on a vastly more extended
scale, in which our moments are measured by millions of years and our
miles by the almost infinite distances of sidereal and nebular space.