AETHER AND STARS AND NEBULAE
ART. 117. _The Starry World._--In addition to the planets and comets
that are found in the heavens, there are other bodies, countless in
their number, which we know as stars. Who has not looked up into the
heavens on some clear night, and noticed how the vault of heaven was
spangled over with points of light, each point representing a huge sun
that exists in far-off space? For it must be remembered that every star
is a sun, which, reasoning by analogy, is the centre of a stellar
system, just in the same way that our sun is the centre of our solar
system. Like our sun, all stars shine by their own light, and the
quality of that brilliancy decides the magnitude of the star, the
magnitude being indicative of the relative brilliancy of a star rather
than its size. So that stars are divided into groups according to their
magnitude, the magnitudes ranging from the first to the sixteenth, and
even beyond. Those of the first magnitude are more brilliant than those
of the second, those of the second more brilliant than those of the
third, each magnitude decreasing in relative brilliancy as the number
which indicates the magnitude increases. There are about sixteen
different degrees of magnitude, in which are classified the millions of
stars that exist in infinite space, but only stars up to the sixth
magnitude are visible to the naked eye, the telescope revealing those
which lie beyond. The total number of stars visible to the naked eye are
about 6000, half of which are visible in each hemisphere.
About 20 stars comprise the group of the first magnitude, which include
all the brightest stars visible, as Sirius, Canopus, Alpha, Arcturus,
Rigel, and Capella.
Those of the second magnitude number about 65, and include the brighter
stars to be found in the constellation known as the Great Bear. Stars of
the third magnitude number about 200, of the fourth magnitude about 400,
of the fifth magnitude 1100, and of the sixth magnitude about 3200.
With the aid of the telescope about 13,000 stars of the seventh
magnitude are revealed to us, and 40,000 of the eighth magnitude, while
of the ninth magnitude over 140,000 are revealed by the telescope. As
the power of the telescope is increased, so the number revealed is
increased also, until by the time we have reached stars of the
fourteenth magnitude, at least 20,000,000 are revealed to us.
If we look into the heavens on a clear moonlight night, we shall further
see that here and there are groups of stars clustered together. These
clusters are termed constellations, and are named after some object
which the arrangement of the stars seemed to suggest. Thus every one is
familiar with that constellation known as the Great Bear, or the
"Plough," so called because of its resemblance to a plough.
The brightest stars of each constellation are named after the letters of
the Greek alphabet, the brightest being called Alpha, the next in
brilliancy Beta, and so on, right through the Greek alphabet. For
example, the seven stars in the Great Bear are known as Alpha, Beta,
Gamma, Delta, Epsilon, Zeta, and Eta.
The constellations are grouped into two divisions, known as the Northern
and Southern constellations respectively.
The visible Northern constellations are 25 in number, and include the
following well-known groups--
Ursa Major The Great Bear.
Ursa Minor The Little Bear.
Draco The Dragon.
Hercules Hercules.
Cygnus The Swan.
Lyra The Lyre.
The visible Southern constellations are 18 in number, and include such
groups as--
Cetus The Whale.
Orion Orion.
Canis Major The Great Dog.
Canis Minor The Little Dog.
Corona Australis The Southern Crown.
Crux Australis The Southern Cross.
_Variable Stars._--Not only are the stars of different magnitudes, but
the brilliancy of some of them changes from time to time. This class of
stars is known as variable stars, and has received the attention of
modern astronomers for many years, in order that the cause of their
variation might, if possible, be ascertained. The periods of variation
differ in length, ranging from a number of days to 60 or 70 years.
One of the most interesting of variable stars is that known as Omicron
Ceti, whose period of change is about 331 days. Its brilliancy varies
from one of the second magnitude to one of the tenth.
Beta Persei is another well-known variable star. This star shines as one
of the second magnitude for 2 days and 13 hours, and then suddenly loses
its light, and in less than 4 hours becomes a star of the fourth
magnitude. Its brilliancy then increases again, and in a similar time it
regains its former brilliancy.
The conclusion that has been arrived at in regard to the cause of the
variation of these stars is, that in each case the diminution of light
is due to the existence of dark bodies, probably planets, which revolve
round the central star.
This hypothesis was confirmed by Professor Vogel about 1889 by means of
spectroscopic results.
Another interesting fact about stars is that they shine with various
colours. The colours of stars are as various as the colours of the
rainbow, and range through the whole spectrum, of red, orange, yellow,
green, blue, indigo, violet, and white. What is more remarkable is the
fact that the colours of the stars seem to change through great periods
of time. If we turn to ancient records we learn that Sirius was red
then, but is now green, while Capella was also red, but is now pale
blue.
_Double and Multiple Stars._--Many stars when looked at through powerful
telescopes are found to be double, triple, quadruple, and even multiple,
although when looked at by the naked eye, they seem to be single in
appearance.
An example of a double star is to be found in the constellation of Lyra.
A moderate telescope reveals this as a double star, while a still more
powerful telescope reveals the strange fact that each apparently single
star which forms the double is itself double, so that we have in this
constellation a system of four stars, in which each pair revolves round
a point situated between them.
Several thousand double stars are known altogether, while the motions of
several hundreds of them have been detected with powerful telescopes.
Some of the double stars are as follows--Zeta Hercules, Eta Coronae
Borealis, Gamma Coronae Borealis, Beta Cygni, Alpha Centauri.
The colours of some of the double stars are very beautiful. Some are
yellow and blue; others, yellow and purple, while others are orange and
green. Some of the double stars are only optical doubles, that is to
say, they apparently seem close together, while as a matter of fact they
are immense distances from each other, the apparent doubleness being due
to the fact that they are more or less in the same line of vision. Real
double stars, where the component stars are situated close together, are
known as physical doubles, to distinguish them from the optical doubles.
_Binary Stars._--Another class of double stars are known as Binary
Stars. This class of stars is composed of two stars which revolve around
each other in regular orbits, and are among some of the most interesting
objects in the heavens. About 1000 Binary stars are known altogether.
Their motions, however, are very slow, and only in a comparatively few
cases have the dimensions of their orbits been ascertained. Some of the
Binary stars are Zeta Hercules, which has a period of about 36 years;
Eta Coronae Borealis, which has a period of 43 years; while the
brightest star, Sirius, is also a Binary star, with a period of about 50
years.
_The Milky Way._--The Milky Way is the name given to that band of light
which stretches across the sky at night-time, and forms a zone or belt
that completely circles the celestial sphere.
This belt of light has maintained from the earliest ages the same
relative position among the stars, and, when resolved by powerful
telescopes, is found to consist entirely of stars scattered by millions
across the expanse of the heavens.
The whole zone or belt is composed of nothing but stars, whose average
magnitude, according to Herschel, is about the tenth.
Stars of all magnitudes are, however, found in this zone.
Of the brightest stars, about twelve are found in this region, while the
majority of stars of the second, third, and fourth magnitudes are also
found in or near it.
The great majority of star clusters are also found along the course of
the Milky Way, while many of the irresolvable nebulae seem to congregate
near the poles of this starry region.
The Milky Way is divided in one part of its course by a stream of stars,
which seems to branch off as a separate stream, thus dividing it into
two parts.
All these facts seem to point to the conclusion that the stars of the
universe, instead of being scattered about haphazard in the space, form
a ring or layer, of which the thickness is very small compared with its
length and breadth.
Our own solar system, according to Herschel, occupies a place somewhere
about the middle of the thickness of the zone, and near the point where
it divides into two parts.
Recent observations go to show that there is a tendency of the sun's
apex to drift along the edge of the Milky Way, and this drift seems to
point to a plane of motion of the sun, nearly coinciding with the plane
of the Milky Way.
ART. 118. _Stars and Kepler's Laws._--We have learned in a previous
chapter that the sun is the centre of a system which comprises a retinue
of planets, with their attendant satellites, together with a number of
asteroids or minor planets, with the addition of meteors and comets to
complete the system.
Now if the sun is a star, then, according to our First and Second Rules
of Philosophy, every star ought also to be the centre of a stellar
system and the centre of two aetherial motions, that is, the Centrifugal
and Centripetal forces, due to the pressures and tensions of the Aether
medium. Further, every stellar system would be composed of exactly
similar bodies to those which compose our solar system, as planets with
their attendant satellites, together with meteors and comets; the whole
of the stellar planets being bound to the central body by the
combination of the two aetherial motions, and kept revolving round the
central star by the rotating electro-magnetic Aether currents.
Such a hypothesis is entirely philosophical, as it is simple in
conception, and fully agrees with our experience in relation to the only
star of which we have any complete knowledge.
It is unthinkable to conceive of a star existing in so-called space, and
constantly radiating out its light and heat for no purpose at all. All
Nature teaches us that there is not a single thing in existence but what
has a definite purpose, and a definite place to fill in the universe.
Even the aetherial atoms, which form the foundation stones of the
universe, have their own purpose to fulfil in the glorious scheme of the
Universe conceived by the Eternal Infinite; and to suppose that a star
has no purpose to fulfil, no task to perform, is to suppose something
altogether opposed to the teaching of all Philosophy. Why even man, with
his finite wisdom, would not be so foolish, so unwise, as to make a
star, and set it in the firmament of heaven for no purpose at all! Are
we therefore to suppose that the Divine Creator of all things possesses
less wisdom than the creatures which He Himself hath made? Such an
assumption would be a reflection not only on the wisdom of an All Wise
Being, but would also be a reflection on our own ideas of philosophical
reasoning.
Therefore the conclusion that we are compelled to come to, in relation
to the millions of stars that exist in interstellar space, is that every
star is the centre of a stellar system, and the centre of two aetherial
motions due to the pressures and tensions of the electro-magnetic
Aether; while rotating round each star are the ever-circulating
electro-magnetic Aether currents, which form the medium by which all the
stellar planets with their attendant satellites are ever made to revolve
around that central body which supplies them with their light and heat.
Some such conclusion as this Sir John Herschel arrived at, for in his
_Treatise of Astronomy_, Art. 592, he writes: "Now for what purpose are
we to suppose such magnificent bodies scattered through the abyss of
space? Surely not to illuminate our nights, which an additional moon of
the 1/1000 part of our own moon would do much better. He must have
studied astronomy to little purpose who can suppose man to be the only
object of the Creator's care, or who does not see in the vast and
wonderful apparatus around us, provisions for other races of animated
beings. The stars, doubtless, are themselves suns, and may perhaps each
in its sphere be the presiding centre around which other planets or
bodies may be circulating."
Further, with reference to the stability of each of these stellar
systems, it is essential that the existence of a physical centrifugal
force should be recognized, in order that the unity and harmony of the
spheres should be maintained.
Professor Challis points this out very conclusively in the _Phil. Mag._
of 1859, where, writing on this point, he states: "It may also be
remarked, that if the Law of Gravity be absolute, there is no security
for the stability of a system of stars, whether the system be a Milky
Way or a nebulous cluster. For, however small the mutual attraction
between the constituent bodies may be, in the course of ages it must
produce a general movement towards the centre or densest region. But the
form of the Milky Way and of certain nebulae seems to present an utter
contradiction to any such tendency." With the conception, however, of a
physical centrifugal force or motion due to the pressure of a physical
medium, the stability of even the Milky Way may be physically conceived
and understood.
Again, when we consider the sun as a star, we find that it has two
motions of its own, one of rotation on an axis, and the other of
translation in an orbit, such rotation being due to the fact that it is
a magnet and has ever circulating round it electro-magnetic Aether
currents (Art. 91). By inference, therefore, we arrive at the fact that
every star is a magnet, as suggested by Professor Schuster, and
possesses rotation on an axis, such rotation being due to exactly the
same cause as produces the rotation of any other planetary or solar body
(Art. 92). Not only has each star a rotation on its axis, but it must
also possess translational motion in an orbit, and that orbital motion
must be due to exactly a similar cause as that which produces the
orbital motion of the sun. Are there any indications given by
astronomical observations which lead us to the conclusion that stars do
possess such orbital motions? The answer is unanimously in the
affirmative; for, although all the stars and the constellations retain
apparently the same relative position to each other, yet they are all in
motion. The actual translational motion of the stars is termed proper
motion, and has been calculated with more or less success in relation to
many of the stars nearest to us. There are other motions of the stars
known as apparent motions, which are easily noted by any observer. These
apparent motions are due to the rotation of the earth on its axis, and
its orbital motion round the sun.
Nothing is more certain, however, than that careful astronomical
observations have revealed the fact that stars have actual orbital
motions of their own through space. In many cases the orbital velocity
has been approximately ascertained.
Halley discovered proper motions of certain stars as far back as 1715,
when he found out, by comparing different observations, that Sirius,
Arcturus, and Aldebaran had moved during the period which had elapsed
since the respective observations were taken.
More recent observations tend to confirm the fact that stars have indeed
proper motions, due to their actual translation through space. It has
been ascertained, for example, that Arcturus is travelling at least 54
miles per second.
The proper motion of the stars, however, only gives us an indication of
their relative motion through so-called space. It does not tell us
whether the star is apparently receding from the earth, or approaching
it.
Dr. Vogel has ascertained by a special system of photography in relation
to the spectra of stars, that Rigel has a velocity away from the earth
of nearly 39 miles per sec., Aldebaran of 30 miles per sec., and Capella
of 15 miles per sec., while the Pole star is apparently approaching the
earth at a rate of nearly 16 miles per sec.
Now if all the stars move through space with varying velocities, as
spectroscopic and telescopic observations seem to suggest, the question
naturally confronts us as to what is the particular kind of orbit which
each star completes? Is the orbit that of an ellipse, or a circle, or a
parabola?
That it must have some kind of orbit is obvious from the proper motions
exhibited by the several stars. We have already learned from Arts. 107
and 108 that the sun possesses an orbit, which orbit fulfils the first
and second of Kepler's Laws.
If therefore the sun, as representing all stars, is subject to Kepler's
Laws, then, according to our Second Rule of Philosophy by which we base
our hypotheses on our experience, we are compelled to come to the
conclusion that every star which possesses any motion at all through
space must also be subject to Kepler's Laws, and therefore must each
possess a controlling centre around which they severally revolve. Kepler
himself was of the opinion that the stars were subject to the laws which
go by his name, and this view of the subject was also accepted by Sir
William Herschel.
Thus from philosophical considerations we affirm that each star, while it
is itself the centre of a starry system, is also dependent upon and
associated with some other body, to which it is held bound by the
electro-magnetic Aether, and around which it is made to revolve by the
circulating electro-magnetic currents associated with that central body.
So that by philosophical reasoning we are led to view the whole of the
innumerable stars that flood interstellar space, not as so many individual
and isolated units, that have no relation to each other, but rather as
parts of one great system, which in its entirety may form in its ultimate
unity one harmonious whole, a universe.
As we come to consider star clusters and nebulae, we shall see how this
idea of unity seems to be manifested throughout all celestial phenomena.
ART. 119. _Aether and Nebulae._--In addition to the host of stars that
flood the infinite space, there are other celestial bodies that meet the
gaze of the astronomer as the telescope is turned upon the heavens.
These bodies, which are glowing masses of gaseous matter, are termed
Nebulae. The word Nebulae signifies a cloud, but they are not clouds in
the same sense as we apply that term to masses of vapour that exist in
our own atmosphere. Sir Wm. Herschel did more towards the discovery of
nebulae than perhaps any other astronomer, either before his time or
since. His labours in the direction were completed and enlarged by his
son, Sir John Herschel, who surveyed the Southern heavens in a way that
had never been accomplished before.
The result of the combined labours of the two Herschels has placed
information of the nebulae at our disposal which is invaluable. Several
thousands of different nebulae are now known to us, and as the telescope
is improved and its powers increased, fresh nebulae are being added to
the number. Like stars, nebulae vary not only in size, but also in
colour, shape, and even in the materials of which they are composed.
They also vary in brightness, the light from some being much fainter
than the light from others.
It has been estimated by Huggins that the light received from a nebula
will not exceed the light of a sperm candle looked at from a distance of
a quarter of a mile. It is thought by some astronomers that the light
received from a nebula is indicative of the stage of development to
which it has arrived. Where the light is faint, the nebulae are in their
first stages of formation, and where it is brighter it is indicative of
a more advanced stage of development. Thus nebulae may consist of
nebulous matter in various stages of condensation, but they are not yet
in that condition which corresponds to the condition supposed to exist
in our sun.
Nearly all the nebulae lie outside the Milky Way, so that it would seem
as if in ages past all the nebulae that had ever existed in this starry
zone had passed out of their nebulous condition and been further
condensed into suns or stars, as they are called. Astronomical
observations teach us that there are very few nebulae indeed to be seen
in this starry highway, the part of the heavens which are richest in
them lying far beyond the confines of this zone. For many years certain
aggregations of luminous points in the heavens were supposed to be
nebulae, but by the aid of more powerful telescopes they have now been
resolved into clusters of stars. One of these clusters is the cluster in
Hercules, while another is the great nebula of Orion. In the case of the
former, situated in the constellation of Hercules, we find a great
number of very small points of light grouped together in a more or less
globular form. When looked at through a small telescope, this object
looks like a nebula, but looked at through Lord Rosse's, or some other
great telescope, it becomes at once resolved into an immense number of
separate points of light, each one representing a star, there being
between one and two thousand altogether in this constellation.
Clusters of stars are usually globular in form, though some are
irregular in outline. The latter are generally rich in stars, with a
less condensation of stars towards the centre. Sir Wm. Herschel
considered the irregular clusters as being in a less advanced stage of
condensation, as he was of the opinion that all groups ultimately tended
to clusters which were globular in form. Before dealing with the
different kinds of true nebulae we will now consider the question as to
"What are Nebulae?"
ART. 120. _What are Nebulae?_--The question which presents itself to the
mind of all astronomers when they have viewed the wondrous nebulae that
exist in far-off space is, "What are Nebulae?" This question is so
closely identified with the question as to "What is Matter?" that the
solution of the one will give us the key to the solution of the other.
It is now generally admitted, that nebulae are composed of a glowing
mass of gaseous matter, that gaseous matter being partly composed of the
gas Hydrogen. Dr. Huggins in 1864 first made the discovery of the
existence of Hydrogen in certain nebulae by means of the spectroscope,
which distinctly revealed certain lines that proved the existence of
Hydrogen in the nebulae.
In the spectra of some of the nebulae, that of 31 Andromeda, for
example, there are no dark lines shown, but only a continuous band of
bright light, which would seem to indicate that there was no glowing
gaseous matter in that nebula at all. But accepting the fact that the
nebulae are composed of glowing gaseous matter, the problem confronts us
as to where this gaseous matter comes from.
If, as spectrum analysis seems to teach us, there are nebulae in various
stages of formation, there must be a period in their history of
development when they had an origin. What, then, is the origin of a
nebula, and what the physical explanation of that origin? From optical
phenomena we learn that all space is not empty, but filled with the
Aether which is universal (Art. 42). What is the relation, then, of this
glowing nebulous matter to this universal Aether? If it be suggested
that there is no relation, then we are in the unphilosophical position
of having to admit, either that the nebulous matter of which the nebulae
are composed never had any origin, or that it had its origin in some
unknown and still undiscovered medium which exists in space. But both of
these hypotheses are unphilosophical, as the former is contrary to all
experience, while the latter is opposed to that simplicity of conception
by which we only postulate one medium, the Aether, to fill all space.
Thus we are led to the conclusion, that the gaseous matter, be it
hydrogen or nitrogen, must have some relation to the electro-magnetic
Aether that is so universal in its extent. Already this relationship has
been dealt with by one who has done more for the development of
aetherial physics than any other scientist. Lord Kelvin, in his paper
"On the Clustering of Gravitational Matter in any part of the
Universe,"[43] has solved this relationship, though in so doing he has
had to depart somewhat from the idea of an incompressible Aether. In
that paper he writes as follows: "If we consider Aether to be matter, we
postulate that it has rigidity enough for the vibrations of light, but
we have no right to say that it is absolutely incompressible. We must
admit that sufficiently great pressure could condense the Aether in a
given space, allowing the Aether in the surrounding space to come in
towards the ideal shrinking surface." In another part of the paper,
dealing with the same question, he writes: "In regions where the density
was greater than in neighbouring regions, the density would become
greater still; in places of less density, the density would become less,
and large regions would quickly become void or nearly void of atoms.
These large void regions would extend so as to completely surround
regions of greater density." He then points out, that as soon as this
density becomes something like the density of the atmosphere, then
collisions would take place between the particles, and continues: "Each
collision would give rise to a train of waves in the Aether. These waves
would carry away energy, spreading it out through the void Aether of
infinite space. The loss of energy thus taken away from the atoms would
reduce large condensing clusters to the conditions of a gas in
equilibrium under the influence of its own gravity, rotating like our
sun or moving at moderate speed as in spiral nebulae. Gravitational
condensation would at first produce rise of temperature, followed later
by cooling, ultimately freezing, giving solid bodies, collision between
which would produce meteoric stones such as we see them."
Here then we have a definitive relationship between Aether and nebulae
given to us from one of the keenest intellects of the present time, but
in order for that relationship to become strictly philosophical, the
conception of the Aether as advanced in this work must be accepted. For
with the present conception of a frictionless Aether, such a hypothesis
is altogether untenable, because it supposes something that is contrary
to all experience and observation.
On the basis of a condensing frictionless Aether into any kind of solid
body, be it nebula, meteor, sun or star, we have to suppose that it is
possible for a medium (the Aether, which is outside the Law of
Gravitation according to the present theory) to be condensed into a
body, that is, a nebula or meteor which is subject to the Law of
Gravitation; and the question arises, at what point in the history of
its condensation does this frictionless Aether pass out of the condition
of having no weight, to the condition when it has weight; or, in other
words, from the condition when it is outside the Law of Gravitation, to
the condition when it comes under the Law of Gravitation?
No satisfactory solution can possibly be offered to such a problem.
Therefore one of two results must follow, either that the Aether is not
frictionless, but possesses weight; or, that the condensation of the
Aether is not possible. With the theory of Aether presented in this
work, the whole question receives a simple and philosophical solution.
As Aether is matter, it is therefore atomic; and being atomic, it is
subject to the Law of Gravitation; and therefore, possessing mass and
weight, it can readily pass into other forms of matter, and with such a
conception Lord Kelvin's hypothesis becomes not only possible but
probable. So that it is exceedingly probable that nebulae are nothing
more nor less than condensed Aether, the same as comets were suggested
to be condensed Aether. It may be asserted that such a hypothesis lacks
that experimental evidence which is so necessary for its establishment,
but I hope to show in the last chapter that Faraday has given the world
that very experimental evidence which will place this hypothesis upon a
firm and solid foundation, and enable it to pass out of the region of
the hypothetical into the region of fact and experiment.
According to our hypothesis, therefore, nebulae are simply condensations
of the electro-magnetic Aether that exists in interstellar space, and
the various spectra of the different nebulae indicate the stage of
development to which the process has arrived. Where the spectra are
bright, and continuous, and free from any dark lines, there we have
simply the Aether in its very first stage of condensation; and where we
have the dark lines appearing, such lines indicate a more advanced stage
to which the process has arrived.
[Footnote 43: _Philosophical Magazine_, July 1902.]
ART. 121. _Nebular Hypothesis._--The Nebular Hypothesis was first
introduced by Kant in his work on the _History of the Earth and Theory
of the Heavens_.
In that work he attempted to explain the origin of the universe on
purely mechanical lines. Laplace, a French mathematician, about the same
time came to similar conclusions as Kant had done, and published his
views in his work on _Exposition du Système du Monde_, and later on in
his more famous work the _Mécanique Céleste_.
A feature common to both these theories rested in the fact, that they
supposed that all material bodies which exist in the universe once
existed in a nebulous condition, and that they were formed out of this
nebulous matter. Further, that this nebulous matter gradually condensed,
and as it condensed, a rotational motion was imparted to them, which
rotation quickened as the condensation was continued.
Then, as the rotation was accelerated, portions were flung off by the
centrifugal force, and these portions of nebulous matter gradually
condensed, forming the various planets of the system. As these
condensed, they, in their turn, parted with some of their nebulous
matter through the repulsive energy of the centrifugal force, and these
secondary parts gave origin to the various satellites that exist round
the planets.
Now, while the general principle involved in the nebular hypothesis is
true, yet the conception according to Laplace is not verified by fact,
as we learn that Uranus and Neptune are still in a state of
self-luminosity, while their density is the smallest of all the planets.
From this we should infer that the two outermost planets are the
youngest planets of our solar system, but according to Laplace's theory,
they ought to be the oldest, as they would have been flung off first by
the parent body as it rotated; and therefore, being flung off first,
should be in a more advanced stage of development than any of the inner
planets. M. Faye has suggested a remedy for this defect in the theory.
He supposes that the nebulous matter out of which the planets were
formed, was not flung off by the central body the sun, but that each
planet was formed at different centres of condensation within the
nebular mass that existed in space. This would, undoubtedly, meet the
difficulty already referred to, and solves the problem as to how the
various planets were formed at different distances in space.
Further, such a solution is in perfect harmony with all the Rules of
Philosophy. It is much more simple to conceive of Aether condensing at
various points in what originally was the solar nebula, than it is to
conceive of Aether condensing and shrinking towards one central point,
and yet while condensing and shrinking, portions were flung off into
space which would form the planet. A greater objection has to be met,
when we come to deal with the origin of all the meteors and minor
planets that exist in their numbers in the solar system. In relation to
their origin, it is much easier to conceive of portions of the Aether
condensing at different centres of condensation, than to suppose that
each portion of aetherial matter that originally formed the meteor, or
asteroid, was flung off as a separate portion from the central body.
With the conception of an atomic and gravitating Aether, the Nebular
Hypothesis, therefore, for the first time is placed upon a sound and
philosophical basis, because the condensation of Aether, which is matter
and possesses mass, admits of the origin of other matter from it which
also possesses mass, together with other properties, as elasticity,
density, compressibility and inertia.
When there is added to the atomic Aether the conception of a rotatory
aetherial atom, as was indicated in Art. 44, we have at once a source
from whence the rotation of the whole mass may be derived. Thus, as the
condensation continued, and the nucleus or central part of the body was
gradually formed, the rotation would be accelerated, because of the
inherent energy which would exist in the condensed part. Further, as the
condensation continued, the body so formed would be more or less
spherical in form, as the conception of our aetherial atom was
spherical, and when we conceive of the primary point of condensation, we
have to think of a large number of spherical atoms coming together; and,
as all the motions of the Aether which give rise to light, heat,
electricity and magnetism, and which now include gravitation, are
spherical in their operations, so their effect upon any condensing
Aether would take a spherical form. Thus such bodies as nebulae, comets,
asteroids, satellites, planets and suns should possess bodies more or
less of a spherical form, subject to certain qualifying conditions, as
rotation and orbital velocity, and this is in harmony with observation
and experience. For we shall find that even in the case of nebulae, we
have globular, ring or annular nebulae, and elliptic nebulae, while in
the case of comets, the nuclei and coma are more or less spherical.
Further, it is a familiar fact that the shape of all asteroids,
satellites, planets, and even the sun is spherical or that of an oblate
spheroid, which latter is simply due to its rotational velocity on its
axis.
Thus the principle involved in the nebular hypothesis receives its
confirmation in the atomic and gravitating Aether, and with certain
modifications of the different hypotheses advanced, is capable of
uniting all those hypotheses that have ever been put forth in this
direction into one perfect and harmonious whole.
Again, the condensation of the Aether, composed as it is of its atoms,
ever in a state of rotation, does away with the Primitive impulse which
was objected to in Art. 9. For in that article it was shown that the
conception of a primitive impulse as conceived by Newton was
unphilosophical, in that its conception was not simple, and failed to
satisfactorily account for observed phenomena. With the hypothesis,
however, of a rotatory aetherial atom, we have at once those conditions
which at any time, in the history of the universe, may give rise to
those conditions by which a body may be set rotating not only on its
axis, but also revolving around some central body, as the process of
condensation is continued.
So that in the primordial and universal electro-magnetic Aether that
exists in all space, we get those conditions which will not only give
rise to the phenomena of light, heat, magnetism and electricity, but
also those properties, qualities and motions by which are produced,
maintained and perpetuated, the various bodies that exist in the Aether,
which is at once the physical source and cause of the bodies.
ART. 122. _Kinds of Nebulae._--Nebulae may be classified into the
following groups--
1. Irregular Nebulae.
2. Ring and Elliptical Nebulae.
3. Spiral or Whirlpool Nebulae.
4. Planetary Nebulae.
_Irregular Nebulae._--Of this class the most conspicuous are those in
the constellations of Orion and Andromeda. So clearly defined are they,
that they are oftentimes seen by the naked eye on a clear night, and are
often mistaken for comets.
The great nebula in Orion is one of the most noticeable objects in the
heavens. It is noted for its size and brilliancy, and also for the
successful observation which it has been subjected to from time to time.
This large nebula is situated in that part of Orion which is occupied by
several stars known as the Sword Handle. These multiple stars are known
by the name of Theta. Around these multiple stars is to be seen the
nebula, as though the multiple stars really were enveloped by the nebula
extending for a great distance out into space. It is of a faint bluish
colour, with the central parts possessing the greatest brilliancy. The
suggestion arises in our mind as to whether the nebulae are in any ways
indicative of the presence of the electro-magnetic aetherial field that
each star undoubtedly possesses. We learned in Art. 88 that the sun is
an electro-magnet, and that it possesses its electro-magnetic field. We
have also seen in Art. 109 that the zodiacal light, which is to be
observed in connection with our solar system, is really indicative of
the presence of that electro-magnetic field, as it rotates round the
central body. Now, if an observer were situated out in space, where the
nebula of Orion is situated, and could look at our system with
telescopes equally as powerful as those we possess, would not our sun
present an equally nebulous light to them because of the presence of its
electro-magnetic field?
Conversely, if every star possesses an electro-magnetic aetherial field,
as they undoubtedly do, then it seems only reasonable to infer that that
electro-magnetic field possesses a nebulosity which corresponds with our
zodiacal light. The fact that the spectra of the nebulae are continuous,
revealing no dark lines, seems to indicate the purity of some of the
nebulae, and that therefore they are free from all known elements.
So that spectroscopic results seem to confirm this hypothesis, as the
pure Aether that would surround every star, or multiples of stars, would
certainly not reveal any dark lines by means of the spectroscope. Such a
hypothesis, as to the real nature of a nebula, is entirely in harmony
with the theory of the Aether presented in Chapter IV., because being
gravitative it will surround each star or multiples of stars, and
therefore be denser nearest to those stars, and being atomic, there will
be a certain amount of nebulosity manifested by the denser parts of the
medium, as is the case in our own solar system.
_Ring or Elliptical Nebulae._--These forms of nebulae are so named from
their ring-shaped appearance, sometimes being known as Annular Nebulae.
The elliptical nebulae are usually classed with them, as they are
supposed to be similar kinds of nebulae looked at edgeways. The best
known of this class is that found in the constellation of Lyra, and
known as 57M, which is the number of the star in Messier's catalogue of
stars. It is small but well-defined, so that it looks more like a flat
oval solid ring than a nebula.
The central part is not entirely dark, but is filled up with a hazy
light. Another annular nebula is that situated to the south-west of
Lambda Scorpii. Sir J. Herschel[44] writes of it thus: "It is a delicate
but well-defined annulus. The field is crowded with stars, two of which
are nebulae. A beautiful delicate ring of a faint ghost-like appearance,
about 40" in diameter, in a field of about 150 stars, of 11 and 12
magnitude and under."
Of the elliptical nebulae the best known is the one in the constellation
of Andromeda, which goes by the name of 31M. It is visible on a clear
night, and can be seen by the naked eye as a hazy light. There are
several other elliptical nebulae, lying to the north-west of this great
nebula.
_Planetary Nebulae._--The planetary nebulae represent a number of minute
objects visible in the heavens. They look like globes of a
bluish-coloured gas and are sometimes mistaken for small stars. Sir J.
Herschel writes about them as follows: "Planetary nebulae are very
extraordinary objects. They have, as their name implies, a resemblance
to planets, presenting discs, round or slightly oval, some being quite
sharply defined, terminating in others a little hazy or softened at the
border. They are comparatively rare objects, not more than 25 having
been observed, and of these nearly three-quarters are in the southern
hemisphere. Their disc is circular or slightly elliptic, with sharp,
clear, and well-defined outline, having exactly the appearance of a
planet with the exception only of its colour, which is full blue,
varying somewhat upon green. M. Arago has surmised that they may
possibly be envelopes shining by reflected light from a solar body
placed in their centre, invisible to us because of its excessive
distance."
The suggestion which arises to our mind in view of the atomic and
gravitating Aether is, that the planetary nebulae are exactly what their
names imply, that is, nebulous matter around planets. We have already
learned that each satellite and planet possesses an electro-magnetic
field, which field takes more or less the shape of a spherical form, so
that if there are planets existing in the far-off systems in space, as
we are compelled to believe that there are, then they too would possess
an electro-magnetic field, which would be composed of spherical
envelopes surrounding the several planets. These planets would shine by
reflected light, as suggested by M. Arago.
The possession by the planet of the nebulous matter, which we have
already suggested is composed of the denser parts of the Aether around
the planet, would give to the planet a nebulous appearance which would
satisfactorily account for the term already given. They would indeed be
what Sir John Herschel suggested they were, viz, planetary nebulae.
_Spiral Nebulae._--The Spiral, or Whirlpool Nebulae, are remarkable
objects, and were first discovered by Lord Rosse with his six-foot
telescope. One of the best examples of the spiral nebulae is that known
as 51M. Small telescopes show this as two clusters, one of them being
surrounded by a ring, at a distance, which is divided into two parts.
Lord Rosse, however, found it to be really a spiral nebula, the ring
running into a series of spiral coils of nebulous matter, the outlying
parts being connected with the main part by curved bands.
Huggins has found that the spectrum of this nebula is not gaseous. Other
examples of this class are 99M and 33M. What these spiral or whirlpool
nebulae are, is unknown, but, on the hypothesis of a condensing and
gravitating Aether which is in a state of rotation, the spiral nebulae
can be easily pictured. For, as the condensation goes on, rotation will
set in, and if we can picture such a phenomenon taking place in a plane
which is at right angles to the line of vision, then we should have a
full view of a nebula which would present a spiral form. Indeed, there
is no phenomenon in connection with nebulae that cannot be physically
explained by a condensing, gravitating and rotatory Aether; and as
Aether is universal, the same properties will apply to it in distant
space as they do in the solar system; and apart from a gravitating and
rotatory electro-magnetic Aether, the phenomena of our own solar system
cannot be physically conceived or explained.
Therefore, if such an Aether can explain the phenomena associated with
our own system, it ought also to explain, and that to the fullest
extent, all phenomena incidental to and associated with the innumerable
systems that flood the universe at large.
[Footnote 44: _Outlines of Astronomy._]