THE CONSTITUTION AND PHENOMENA OF THE SUN.
The various theories thus reviewed, while not sufficient in themselves
to account for the facts of our own solar system, are fatally defective
in another respect. While they aim to account for the sun's light
and heat, they all fail to consider the active medium of the solar
light and heat in the sun itself. It is not simply a highly-heated
central mass glowing in space. It is a vast orb surrounded by
different envelopes of incandescent vapors or gases, and by far
the most vast in volume, as well as in light and heat-radiating
power, are the photosphere and its superincumbent chromosphere,
composed almost entirely of free hydrogen gas in a state of intense
incandescence. Whence comes this enormous mass of hydrogen? And
how explain the entire absence of free hydrogen gas from our own
atmosphere and its replacement by oxygen? There is a recent theory
propounded by Mr. A. Mott, which is set forth in detail in Professor
Ball's "In the High Heavens," and which endeavors to account for the
remarkable absence of free hydrogen gas from the earth's atmosphere,
for, as the author states, "It is a singular fact that hydrogen in
the free state is absent from our atmosphere." The theory, in brief,
is that the molecules of hydrogen gas have an average speed of about a
mile a second,--which, however, is only one-seventh that required to
shoot them off into space,--but that these molecules are continually
changing their velocity, and may sometimes attain a speed of seven
miles a second; the result is that "every now and then a molecule
of hydrogen succeeds in bolting away from the earth altogether
and escaping into open space." During past ages the molecules of
hydrogen would thus have gradually wiggled up through the air, and
finally disappeared into outer darkness for good and all; and thus
"the fact that there is at present no free hydrogen in the air over
our heads may be accounted for." Since the molecules of oxygen have
only a velocity of a quarter mile a second, that unfortunate gas
remains behind and is consumed.
The first difficulty with this theory is to explain how, if the
hydrogen wiggled off in this unceremonious manner, it ever wiggled
on. There is no objection to a gait of this rapidity, however; it
is highly creditable, in fact; but we have a right to expect some
degree of consistency in even so light-headed a body as hydrogen
gas. The article quoted thus continues: "If the mass of the earth
were very much larger than it is, then the velocities with which
the molecules of hydrogen wend their way would never be sufficiently
high to enable them to quit the earth altogether, and consequently we
might in such a case expect to find our atmosphere largely charged with
hydrogen." It will be seen that, according to this theory, hydrogen is
able to achieve a speed of seven miles per second under exceptional
excitement, and that this molecular velocity is just enough, and no
more than enough, to give it egress. We know that Jupiter's mass is
three hundred times as great as that of the earth, and the attraction
of gravity is so powerful on the surface of that planet that, as the
writer just quoted says, "Walking, or even standing, would involve the
most fearful exertion, while rising from bed in the morning would be a
difficult, indeed, probably, an impossible, process." We also know that
the atmosphere of this planet is laden with enormous clouds floating
at various altitudes and with incessant movements. We are told that
"the molecular speed of aqueous vapor averages only one-third of that
attained by the molecules of hydrogen." Of course, on the planet
Jupiter, hydrogen would have no chance of escape at all: it would
just have to stay and take it, like the rest of us. Jupiter must thus
have an atmosphere like our own, except that it is "largely charged
with hydrogen." Of the clouds upon this planet, Professor Ball says,
"In fact, the longer we look at Jupiter the more we become convinced
that the surface of the planet is swathed with a mighty volume of
clouds so dense and so impenetrable that our most powerful telescopes
have never yet been able to pierce through them down to the solid
surface of the planet." With the densities, molecular velocities,
and specific gravity of the oxygen, nitrogen, and the hydrogen, with
which latter the atmosphere of Jupiter must be "largely charged," as
it is said, it is difficult to understand how such enormous clouds
of aqueous vapors, themselves composed of oxygen, which is a very
slow-footed gas, and hydrogen, could travel about with such facility;
we ought to find them packed down like London fog, to say the least,
upon the surface of that planet, with the supernatant gases all
adrift overhead. Jupiter is a hot body; it has not yet cooled down;
and if it is provided with volcanoes, such as its great red spot and
the analogies of the earth and moon would suggest, we can tell pretty
nearly what would have happened long ago with a Jovian atmosphere like
ours; but "largely charged with hydrogen," if we compare it with,
say, an equal mass of dynamite touched off by a volcanic explosion;
there would not have been enough of old Jupiter left to swear by, and
what was left would not have had any atmosphere at all. On Mars, the
same writer thinks the oxygen would still cling, like the fragrance of
the rose, but that all the molecules of the fleet-footed and excitable
hydrogen would long since have taken French leave, as it did from the
earth; but at the moon, on account of its small size and mass, both
gases would have gone off incontinently together. "It is now easy,"
the author says, "to account for the absence of atmosphere from the
moon.... Neither of the gases, oxygen or nitrogen, to say nothing of
hydrogen, could possibly exist in the free state on a globe of the
mass and dimensions of our satellite.... Indeed, the weight of every
object on the moon would be reduced to the sixth part of that which
the same object has on earth." Nevertheless, it may be said that
the moon has considerable weight, as weights go, but with a comet
it is quite a different matter. "These bodies," the author says,
"demonstrate conclusively that the quantity of matter even in a
comet is extremely small when compared with its bulk. The conclusion
thus arrived at is confirmed by the fact that our efforts to obtain
the weight of a comet have hitherto proved unsuccessful.... It has
thus been demonstrated that, notwithstanding the stupendous bulk of
a great comet, its mass must have been so inconsiderable as to have
been insufficient to disturb even such unimportant members of the
solar system as the satellites of Jupiter." Now, here is a state of
things; for the spectroscope shows that comets are fully provided with
a large supply of hydrogen, enough and to spare for ornament, even,
and of nitrogen also, while it is the abnormally fugacious oxygen
which has, apparently, taken its departure. Of course, such facts
demonstrate the untenability of the theory, which is, besides, in
direct contradiction with the laws governing gaseous diffusion. Gases
pass into each other with the same velocity as into a vacuum, and
it is not to be imagined that the molecules of hydrogen could thus
move individually off, unless forced upward by the pressure of some
other gas, which the law of gaseous diffusion makes impossible. We
should as readily expect to see a tumbler full of iron balls, into
the interstices of which loose sand has been poured, manifest a
similar phenomenon by the wiggling out of the less dense sand at the
top of the glass. One might also ask whence, if this theory had any
substantial basis, could come the enormous volumes of hydrogen gas
in the atmosphere of a new or temporary star, in a few hours, or the
changes manifested in the atmospheres of the variable stars. So, also,
the nebular or any other hypothesis of creation would be impossible
under this theory, as the heavier and less mobile gaseous elements
would remain behind, or be condensed nearest the center of gravity of
the aggregating nebula, while the more rapid gases would disappear
outwardly, and in consequence the sun would be found to be composed
of the heavier elements exclusively, and each of the planets, in
turn, would consist of only one or two elements, in accordance with
the more and more mobile character of their molecular movements, and
the uniformity of chemical constitution between the sun and planets,
as well as the fixed stars, would not be found to exist. The theory,
in fact, is an example of the endeavor to explain an easily understood
difficulty by a less easily understood impossibility.
None of the different theories even attempt to account for the
prodigious volumes of hydrogen in the solar atmosphere, and without its
presence the sun, so far as we know, would be almost an inert mass,
considered as a source of energy for the supply of our planetary
system. We know, of course, that meteors contain sometimes as much
as six volumes of gases, largely composed of hydrogen, at our own
atmospheric pressure. But the pressure at the sun's surface is more
than twenty-seven times that at the surface of the earth, and yet the
volume of hydrogen there existing visibly is vaster beyond computation
than any possible mass of meteoric material could supply. So, also,
while it may be granted that condensation of volume must vastly raise
the solar temperature, how could it produce the enormous masses of
hydrogen, the lightest of all the elements, unless they have been
temporarily occluded and finally thrown out from within, which is
impossible? These vast volumes of hydrogen are to be considered first
of all in any attempt whatever to solve the problem of the source
and mode of solar energy.
Considering the phenomena presented within the limits of our own solar
system alone, we find that the earth is one of a single family of
planets, each of which very closely resembles it, and all of which
circle, in slightly elliptical orbits, at various distances around
the sun, their orbits occupying substantially the same plane,
thus making our solar system a flat disk of space occupied by
the sun as a center, with the planets and their satellites moving
harmoniously around it. The planets differ from each other in size,
mass, and temperature, but each is surrounded by an envelope of
aqueous vapor, suspended in an atmosphere substantially like our
own. Professor Proctor, in his "Light Science for Leisure Hours,"
says of the planet Jupiter, "His real surface is always veiled by
his dense and vapor-laden atmosphere. Saturn, Venus, and Mercury
are similarly circumstanced." Of Mars he says that it is "distinctly
marked (in telescopes of sufficient power) with continents and oceans
which are rarely concealed by vapors." Now, whence comes this aqueous
vapor surrounding all the planets? Whether received originally from
the diffused nebular mass from which our solar system is supposed
to have been condensed, or attracted by the force of gravity from
interplanetary space, like the meteors which fall upon the earth's
surface, it is evident that interplanetary space must once have been
pervaded with aqueous vapor, since the nebular mass from which our
solar system was constituted must have occupied at least the space
embraced within its largest planetary orbit, and doubtless much more;
and if so, such aqueous vapor, and other vapors also, must still
persist in space, just as the meteoric particles which so constantly
manifest themselves in our atmosphere. If the planets had no common
origin, the evidence is equally conclusive, since then this identical
substance could only have been derived from a common source, which
can only be interplanetary space. This also is in accordance with
the laws of attraction, which would operate to gather and condense
the rarefied aqueous vapor of space around the planetary masses in
definite proportions. In his "Familiar Essays on Scientific Subjects,"
Professor Proctor says, "In fact, we do thus recognize in the spectra
of Mars, Venus, and other planets the presence of aqueous vapor in
their atmosphere;" and in his "Mysteries of Time and Space" he says,
"We may admit the possibility that the aqueous vapor and carbon
compounds are present in stellar or interplanetary space." But
in addition to this aqueous vapor which surrounds the planetary
bodies, we find free oxygen in vast quantities, and, with this, free
nitrogen in mechanical admixture, and these together constitute the
atmosphere we breathe, and which sustains organic life by a process
of slow combustion. But we find no free hydrogen either in our own
atmosphere or in that of other planets. Turning now to the sun, we
find that it is surrounded by an atmosphere as well as the planets,
but that this atmosphere is composed not of free oxygen, but of free
hydrogen. In his article, "Oxygen in the Sun," Professor Proctor says,
"Fourteen only of the elements known to us, or less than a quarter
of the total number, were thus found to be present in the sun's
constitution; and of these all were metals, if we regard hydrogen as
metallic.... But most remarkable of all, and most perplexing, was the
absence of all trace of oxygen and nitrogen, two gases which could
not be supposed wanting in the substance of the great ruling center
of the planetary system." The researches of Dr. Draper indicated,
however, that oxygen could be found in the sun; not in his external
atmosphere but far down within his surface. Professor Proctor says,
"Dr. Draper mentions that he has found no traces of oxygen above the
photosphere." Such free oxygen cannot be associated with the hydrogen,
however, even if its presence be finally determined, but it may be
due to the deoxidation of solid compounds precipitated upon the sun
from space, and held at a temperature above that of disassociation,
as hydrogen is sometimes generated at the surface of the earth.
The vast mass of the solar atmosphere is composed of hydrogen gas, with
which are found commingled vapors of the various elements which enter
into the sun's constitution, and this solar atmosphere corresponds
in proportion, speaking generally, with our own atmosphere, except
that the volume of solar hydrogen is vastly greater than that of
terrestrial oxygen, for the reason, as will be explained, that water
contains two volumes of the former to one of the latter.
In Appleton's Cyclopædia the sun is thus described, (article by
Professors Langley and Proctor): "To sum up briefly the received
hypotheses of the physical constitution of the sun: of its internal
structure we know nothing, but we can infer, from the low density of
the solar globe as a whole, that no considerable portion is solid or
liquid. The regions we examine appear to consist of cloud layers at
several levels floating in a complex atmosphere, in which probably
most of the elements are known to us, and certainly many of them
exist in the form of vapor. Outside this complex atmosphere extend
envelopes of simpler constitution, though into them occasionally
arise the vapors which ordinarily lie lower down. The sierra, for
instance, consists in the main of glowing hydrogen gas and that gas,
whatever it may be, which produces the line near the orange-yellow
sodium lines. The prominence region may be regarded as simply the
extension of the sierra." Of these prominences, Professor Ball says,
"The memorable discovery made by Janssen and Lockyer, independently, in
1868, showed that the prominences could be observed without the help of
an eclipse, by the happy employment of the peculiar refrangibility of
the rosy light which these prominences emit.... We can now obtain, not,
as heretofore, merely isolated views of special prominences through
the widely opened slit of the spectroscope, but we are furnished,
after a couple of minutes' exposure, with a complete photograph of
the prominences surrounding the sun.... The incandescent region of
the chromosphere from which these prominences arise is also recorded
with accuracy." Resuming our quotation from Appleton's Cyclopædia:
"The inner corona is still simpler than the sierra, so far as its
gaseous constitution is concerned; but here meteoric and cometic matter
appears, extending to the outer corona and to great distances beyond
even the visible limits of the zodiacal. Returning to the photosphere,
we find it subject to continual fluctuations, both from local causes
of agitation and from the subjacent vapor acting by its elasticity to
burst through it; the faculæ, which are found to be above the general
level of the photosphere, are taken to be heapings up of the luminous
matter like the crested surges of the sea. All the strata are subject
to great movements, which sometimes have the character of uniform
progression analogous to our trade-winds, and sometimes are violent,
and resemble in their effects our tornadoes and whirlwinds. Eruptive
action appears to operate from time to time with exceeding violence,
but whether the enormous velocities of outrush are due to true
explosive action (which would compel us to believe that the sun is
enclosed by a liquid shell, so as to resemble a gigantic bubble) or to
the uprising of lighter vapors from enormous depths, as heated currents
rise in our own atmosphere, is not as yet certainly known." The
sierra, or chromosphere, is thus described in the same article:
"The sierra presents four aspects: 1, smooth with defined outline;
2, smooth but with no defined outline; 3, fringed with filaments;
and, 4, irregularly fringed with small flames. The prominences may
be divided into three orders,--heaps, jets, and plumes. The heaped
prominences need no special description. The jets ... originate
generally in rectilinear jets either vertical or oblique, very bright
and very well defined. They rise to a great height, often to a height
of at least eighty thousand miles, and occasionally to more than twice
that; then bending back, fall again upon the sun like the jets of our
fountains. Then they spread into figures resembling gigantic trees
more or less rich in branches. Their luminosity is intense, insomuch
that they can be seen through the light clouds into which the sierra
breaks up. Their spectrum indicates the presence of many elements
besides hydrogen. When they have reached a certain height they cease
to grow, and become transformed into exceedingly bright masses, which
eventually separate into fleecy clouds. The jet prominences last but
a short time--rarely an hour, frequently but a few minutes,--and they
are only to be seen in the neighborhood of the spots. Wherever there
are jet prominences there also are faculæ. The plume prominences are
distinguished from the jets in not being characterized by any signs of
an eruptive origin. They often extend to an enormous height; they last
longer than the jets, though subject to rapid changes of figure; and,
lastly, they are distributed indifferently over the sun's surface. It
would seem that in the jets a part of the photosphere is lifted up,
whereas in the case of plumes only the sierra is disturbed." Of these
eruptions Professor Ball says, "Vast masses of vapors are frequently
expelled from the interior of the sun by convulsive throes with a
speed of three hundred, four hundred, and sometimes nearly a thousand
miles a second.... The spectroscope enables the observer actually to
witness the ascent of these solar prominences."
The corona, which extends beyond the chromosphere, has been determined
by its continuous spectrum to be a vast envelope extending at
least a million miles from the sun's surface. "It cannot be a solar
atmosphere," Professor Proctor observes in his article on this subject,
in his "Mysteries of Time and Space."... "It will be seen, then,
how inconceivably great the pressure exerted by a solar atmosphere
some eight thousand times as deep as ours would necessarily be,
let the nature of the gases composing it be what it may."... "If a
man could be placed on the solar surface, his own weight would crush
him as effectually as though while on earth a weight of a couple of
tons were heaped upon him.... Now, it happens that we know quite well
that the pressure exerted by the real solar atmosphere, even close
by the bright surface which forms the visible globe of the sun, is
nothing like so great as it would be if the corona formed part of
that atmosphere." In the article "Sun," in Appleton's Cyclopædia,
it is stated that "Mr. Arthur W. Wright, of Yale College, has
succeeded in showing that this light (the zodiacal) is not emitted
from incandescent gas, but reflected from particles or small bodies,
and hence derived from the sun."... "There is reason to believe that
the true solar corona extends much farther (than a million miles),
and that, in reality, the zodiacal light forms the outer part of the
solar corona." Proctor, again, in his article on the corona, says,
"It would seem to follow that the corona is due to bodies of some sort
travelling around the sun, and by their motion preserved either from
falling towards him (in which case the corona would quickly disappear)
or from producing any pressure upon his surface, as an atmosphere
would." In his article on "The Sun as a Perpetual Machine," he says,
"There is every reason for regarding the zodiacal as consisting in
the main of meteorolithic masses, a sort of cosmical dust, rushing
through interplanetary space with planetary velocities. To such
matter, assuming, as we well may, that space really is occupied
by attenuated vapors, ... the luminosity of the zodiacal would be
attributable to particles of dust emitting light reflected by the sun
or by phosphorescence (this last may be seriously questioned). But
there is another cause for luminosity of these particles which may
deserve a passing consideration. Each particle would be electrified
by gaseous friction in its acceleration, and its electric tension
would be vastly increased in its forcible removal, in the same way
as the fine dust of the desert has been observed by Werner Siemens
to be in a state of high electrification on the apex of the Cheops
Pyramid. Would not the zodiacal light also find explanation by slow
electric discharges backward from the dust towards the sun?" It may be
observed in passing that such electrical glow is much more prominently,
and more likely to be, the result of induction than of friction. In
the article "Sun," previously quoted, Professor Young says, "There is
surrounding the sun, beyond any further reasonable doubt, a mass of
self-luminous gaseous matter, whose spectrum is characterized by the
green line 1474 Kirchhoff. The precise extent of this it is hardly
possible to consider as determined, but it must be many times the
thickness of the red hydrogen portion of the sierra, perhaps, on an
average, 8' or 10', with occasional horns of twice that height. It
is not at all unlikely that it may even turn out to have no upper
limit, but to extend from the sun indefinitely into space." In the
same article the sun's apparent diameter is placed at about 32',
so that the thickness of the above gaseous envelope would be not
less than one-fourth the sun's diameter, or more than two hundred
thousand miles. This coronal envelope, extending out from the solar
body until gradually merged into the attenuated matter of space, has
a light so feeble that it can only be clearly observed during total
eclipse. Professor Ball ("In the High Heavens") says, "The sunlight
is so intense that if it be reduced sufficiently by any artifice,
the coronal light also suffers so much abatement that, owing to its
initial feebleness, it ceases altogether to be visible." During the
great eclipse of 1893 it was photographed, and of these photographs
the same author says, "One of the most remarkable features in the
structure of the corona is the presence of streamers or luminous
rays extending from the north and south poles of the sun. These
rays are generally more or less curved, and it is doubtful whether
the phenomena they exhibit are not in some way a consequence of the
rotation of the sun. This consideration is connected with the question
as to how far the corona itself shares in that rotation of the sun
with which astronomers are familiar. I should perhaps rather have
said that rotation of the sun's photosphere which, as the sun-spots
prove, is accomplished once every twenty-five days. Even this shell
of luminous matter does not revolve as a rigid mass would do. By some
mysterious law the equatorial portions accomplish their revolution in
a shorter period than is required by those zones of the photosphere
which lie nearer the north and south poles of the luminary. As to how
the parts of the sun which are interior to the photosphere may revolve,
we are quite ignorant.... We have no means of knowing to what extent
the corona shares in the rotation. It would seem certain that the
lower parts which lie comparatively near the surface must be affected
by the rapid rotation of the photosphere; but it is very far from
certain that this rotation can be shared to any great extent by those
parts of the corona which lie at a distance from the sun's surface
as great as the solar radius or diameter.... The corona presents a
curious green line that seems to denote some invariable constituent
of the sun's outer atmosphere, but the element to which this green
line owes its origin is wholly unknown." The same author quotes from
Dr. Huggins as follows: "It is interesting to read what Dr. Huggins
has to tell us about the solar corona. The nature of this marvellous
appendage to the sun is still a matter of uncertainty. There can,
however, be no doubt that the corona consists of highly-attenuated
matter driven outward from the sun by some repulsive force, and it is
also clear that if this force be not electric, it must at least be
something of a very kindred character.... So far as the spectrum of
the corona is concerned, we may summarize what is known in the words
of Dr. Huggins: 'The green coronal line has no known representative
in terrestrial substances, nor has Schuster been able to recognize any
of our elements in the other lines of the corona.'" The account given
by General Myer--quoted in Professor Proctor's article, "The Sun's
Corona"--of the great eclipse of 1869, as viewed from an altitude
of five thousand five hundred feet above sea-level, is as follows:
"As a centre stood the full and intensely black disk of the moon,
surrounded by an aureola of soft bright light, through which shot out,
as if from the circumference of the moon, straight, massive silvery
rays, seeming distinct and separate from each other, to a distance
of two or three diameters of the lunar disk; the whole spectacle
showing as upon a background of diffused rose-colored light. The
silvery rays were longest and most prominent at four points of the
circumference, ... apparently equidistant from each other. There was
no motion of the rays: they seemed concentric." Three diameters would
make these rays extend two and a half million miles at least from the
sun's photosphere, or even its chromosphere. The coincidence between
these rays and those observed (see above) in the eclipse of 1893 must
be noted, since these latter were conceived at one time to be meteor
streams. As those seen in 1893 radiated from the poles, and were curved
in form, while those last noted radiated at four equidistant points,
none polar, and were straight, it will be seen that, if both phenomena
were of the same class, they could not have been due to meteor streams.
The sun's spots, which we will next refer to, are deep,
relatively dark, but in fact extremely bright depressions in the
photosphere. "Many spots are of enormous size" (see article, "Sun");
"one had a diameter exceeding fifty thousand miles, and many far larger
than this have been seen. The spots are not scattered over the whole
surface of the sun, but are for the most part confined to two belts
between latitude five degrees and thirty degrees, on either side of the
solar equator. An equatorial zone six degrees wide is almost entirely
free from spots.... The inclination of the solar equator is about
seven degrees.... The spots on the sun usually have a dark central
region called the umbra, within which is a still darker part called
the nucleus, while around this there is a fringe of fainter shade than
the umbra, called the penumbra. Although the umbra and nucleus appear
dark, however, it is not to be supposed that they are really dark;
... though the nucleus looks perfectly black by contrast with the
general surface, it shines in reality with a light unbearably brilliant
when viewed alone, while his thermal measurements show that the heat
from the nucleus is even greater proportionately than the light, and
not very greatly below the heat of the surrounding surface.... The
recognition of a nucleus within the umbra would seem to indicate that
a third cloud layer (besides the outer or photosphere and a darker
cloud layer beneath) exists within the second or internal layer of
Herschel's theory. But the observations of Professor Langley show that
most probably all the features of the solar photosphere yet observed
are phenomena of cloud envelopes, since he has been able to recognize
cloud forms at one level floating over cloud forms at a lower level,
while even in the (relatively) darkest depths of the nucleus clouds
are still to be perceived, though so deep down that their outlines
can be barely discerned." Professor Ball says of the heat-wave of
1892, "As to the activity of the sun during the past summer, a very
striking communication has recently been made by one of the most
rising American astronomers, Mr. George E. Hale, of Chicago. He has
invented an ingenious apparatus for photographing on the same plate
at one exposure both the bright spots and the protuberances of the
sun.... On the 15th of July a photograph of the sun showed a large
spot. Another photograph taken in a few minutes exhibited a bright
band; twenty-seven minutes later a further exposure displayed an
outburst of brilliant faculæ all over the spot. At the end of an
hour the faculæ had all vanished and the spot was restored to its
original condition. It was not a mere coincidence that our magnetic
observatories exhibited considerable disturbances the next day, and
that brilliant auroras were noted." Carrington's observations have
shown that spots in different solar latitudes travel at different
rates. "Taking two parts of the visible solar surface in the same
longitude, but one in latitude forty-five degrees (say), the other on
the equator, the latter will advance farther and farther in longitude
from the former, gaining daily about two degrees, so that in the
course of about one hundred and eighty days it will have gained a
complete revolution. That is to say, the sun's equator makes about two
revolutions more per annum than regions in forty-five degrees north
and south solar latitude." The sun is about 850,000 miles in diameter;
its density is one-fourth that of the earth; its mass is 316,000 times
greater, and its volume 1,253,000. Gravity at its surface is 27.1 times
that of the earth; its distance is approximately 92,000,000 miles;
it rotates upon its axis, which is inclined to the planetary plane at
an angle of seven degrees, once in twenty-five and one-third days,
apparently increased to thirty days by the earth's orbital advance
in the same direction around the sun; and it has a motion around its
center,--a true orbital motion,--due to displacement by gravity of
the planetary masses, which, however, is always within its own mass.
The above, in brief, is, so far as we know, the constitution of
the sun and its appendages. Its internal globe is surrounded by
a glowing gaseous envelope, the photosphere, which is the visible
orb, composed of cloud masses of glowing hydrogen gas intermingled
with vapors of many of our terrestrial elements, all in a state
of apparent disassociation. Of the constitution of the sun's mass,
Professor Ball says, "Professor Rowland has shown that thirty-six
terrestrial elements are certainly indicated in the solar spectrum,
while eight others are doubtful. Fifteen elements have not been
found, though sought for, and ten elements have not yet been compared
with the sun's spectrum. Reasons are also given for showing that,
though fifteen elements had no lines corresponding to those shown in
the solar spectrum, yet there is but little evidence to show that
they are really absent from the sun. Dr. Huggins epitomizes these
very interesting results in the striking remark, 'It follows that
if the whole earth were heated to the temperature of the sun, its
spectrum would resemble very closely the solar spectrum.'" Outside
the photosphere is the simpler chromosphere, composed largely of
hydrogen, and merging into the corona at a distance of hundreds of
thousands of miles from the sun's apparent surface, and this corona
extends outward to a vast distance, and is itself largely composed
of self-luminous matter, the action of gravity being counterbalanced
by the centrifugal force of orbital rotation, or more probably by
electrical repulsion. The metallic vapors in the sun's photosphere
are suspended in glowing hydrogen, which vastly preponderates over
all the others in mass and volume, the incandescence of which is
the principal source of solar light and heat. The planets revolve
in elliptical orbits around this central sun, and crossing these
orbits at various angles rush streams of cometic matter and comets
and meteoric bodies, in streams and clouds, which, swiftly sweeping
around at various distances, are again thrown off into space. Meteors
constantly fall into the sun's mass, as they do upon the earth; but the
grand key-note of all his life and energy, so far as we can perceive,
is the vast envelope of glowing hydrogen gas.
Conversely, the planetary envelopes are of relatively cool oxygen
mixed with nitrogen gas, which hold in suspension diffused aqueous
vapors. If our own aqueous vapors are derived by the attraction of
gravity from the interplanetary space, as they must have been, we can
be sure that, were the sun at a sufficiently low temperature, he, too,
would gather to himself a surrounding envelope of aqueous vapor, larger
than our own in proportion to his mass, and larger than that of all
the planets together, the combined mass of which he exceeds by seven
hundred and fifty times. We should also expect similar aggregations
of aqueous vapors to surround all the fixed stars in proportion to
their various masses, yet we do not find aqueous vapor there, but
hydrogen instead. And in the distant telescopic nebulæ we still find
hydrogen and nitrogen; even in the comets we find free hydrogen in
vast predominance, but not free oxygen; so that we may roughly divide
the bodies of stellar space into two grand categories,--those with
atmospheres of hydrogen and those with atmospheres of oxygen. It is
true that the latter are limited to the planets of our own system, so
far as direct observation goes, for we cannot see such dark planets
as exist beyond our own solar system; but if such planets exist,
as they must, for reasons stated later on, and revolve around their
own central suns, we may infer, with the strength of demonstration
almost, that if their suns correspond to our sun in this respect, their
planets will correspond to our planets in a similar respect. But the
bodies with atmospheres of oxygen are those which rotate around the
sun substantially as a center, while with reference to themselves the
sun is more or less a fixed body in space. It is true that our whole
system is drifting through space, at present in the direction of the
constellation Lyra, and directly away from that portion of space
occupied by Sirius and Canopus, with an annual motion of probably
hundreds of millions of miles. Professor Ball ("In the High Heavens")
says, "In conclusion, it would seem that the sun and the whole solar
system are bound on a voyage to that part of the sky which is marked
by the star Delta Lyræ. It also appears that the speed with which
this motion is urged is such as to bring us every day about 700,000
miles nearer to this part of the sky. In one year the solar system
accomplishes a journey of no less than 250,000,000 miles." A speed of
eight miles per second gives an annual rate of 252,288,000 miles. This
speed, however, is greatly exceeded by many stars (as determined
by displacement of the lines of the spectrum); the star No. 1830,
of Groombridge's catalogue (see "In the High Heavens"), has a rate
of two hundred miles per second. The author says, "Indeed, in some
cases stellar velocities are attained which appear to be even greater
than that just mentioned. We do not, therefore, make any extravagant
supposition in adopting a speed of twenty miles per second," which
he takes as the average. "I have adopted this particular velocity as
fairly typical of sidereal motions generally. It is rather larger than
the speed with which the earth moves in its orbit." The distances,
of course, are equally enormous. This author says, "The nearest star,
as far as we yet know, in the northern hemisphere is 61 Cygni.... I
think we cannot be far wrong in adopting a value of fifty millions
of millions of miles.... In the course of a million years a star with
the average speed of twenty miles a second would move over a distance
which was about a dozen times as great as the distance between 61
Cygni and the solar system." This assuming that the solar system is
at rest, which is not the case, as the author says, "Unless binary,
stars do not remain in proximity, so far as we know; the general rule
appears to be that of universal movement through space." This drift
through space, however, no more affects the terms of the problem than
the rotation of the earth upon its axis or its orbital motion affects
the operations of an electric machine as the handle may be rotated to
or from the direction of these motions. Both machine and reservoir
of energy occupying a fixed relation with reference to each other,
the positions of each are the same as though absolutely fixed. This
is true of gravitation, likewise, as well as of all other natural
and universal forces.
The fact established, then, that attenuated aqueous vapor is
diffused throughout the interplanetary space occupied by our own
solar system, and that it tends to surround our sun and planetary
bodies with aqueous envelopes of increased density, proportionate to
the action of gravity, the question arises, Is there any known force
which will act through such interplanetary space to decompose such
aqueous vapor into its constituent elements and deposit hydrogen gas
around the sun and oxygen gas around the planets, and which, while
maintaining a planetary temperature such as we find on the planets,
will at the same time raise the hydrogen envelope of the sun to such a
temperature of incandescence that it will become a glowing sphere of
heated hydrogen, in which other constituents of the sun's mass will
be raised to incandescence and partially volatilized in the intense
heat of that incandescent gas; in which, in fact, the phenomena of
the sun will become manifest? If so, two vastly important corollaries
are inevitable: first, that the fixed stars, which also shine with
the light of their own glowing hydrogen, are themselves surrounded by
a similar aqueous vapor, diffused through their own adjacent space,
and that, in consequence, not only our own planetary distances, but all
interstellar space, as far as the utmost distance of the faintest fixed
stars, is likewise pervaded by the same attenuated aqueous vapor, and
that this is the grand source from which is derived all solar energy,
not only of our own sun, but of all the other flaming orbs of space;
and, second, which is still more important to us as citizens of the
universe, that each flaming hydrogen sun must have surrounding it a
correlative dark planetary system of its own, and that the complement
of glowing hydrogen, as an incandescent envelope of the central
orb, necessitates the corresponding supplement of cool oxygen as
an envelope for each of such planetary bodies; in other words, that
without such planets as our system possesses, there can be no suns such
as our own and the other suns we see. Vast orbs might be conceived
of as rotating in eternal darkness without associated satellites,
but the incandescent atmosphere of hydrogen must have--not may have,
but must have--subordinate planets substantially similar to ours,
surrounded by atmospheres substantially similar to our own (for we
find free nitrogen in comets, in meteorites, and in the faintest
nebulæ), and these planets are thus fitted, so far as we can know,
for the support of organic life and for the same orderly courses
of nature as we see manifest around us. They must be cool, for at
the planetary poles there must be a moderate temperature in contrast
with the solar pole, which becomes, of necessity, highly heated; they
must have an atmosphere of oxygen in order that the solar center may
have an atmosphere of hydrogen; these planetary atmospheres must be
supplied with nitrogen, because nitrogen is universally available,
and similar causes operating under similar circumstances will produce
like effects; these atmospheres must be charged with condensed aqueous
vapors, and, if cool enough, must have deposited water in liquid form,
for aqueous vapors when condensed by gravity are the correlated sources
of supply of their respective gaseous components at both solar and
planetary poles; and these planets must rotate in orderly periods
around their central suns, or the aqueous vapors cannot be regularly
and continuously disassociated into their elemental gases. These
planets may be few or many--perhaps even a single one sometimes--for
each sun, but they must be large enough or numerous enough to operate
by their aggregate mass, so as to disassociate around the planets
as much oxygen as their central sun disassociates of hydrogen in
their combining proportions,--that is, two volumes of hydrogen for
each one of oxygen. We will therefore find in such planets all the
potentialities of life--we can see and study these planets, though
physically invisible, as easily and as thoroughly as we do our own,
for having the relationship of constitution between our own planets
and our sun, we may thereby learn the essential relationship between
any fixed star and its planets by directly studying the constitution
of such star alone. Among the planets of our own system Neptune and
Mercury, and those which exist adjacent to their boundaries, can be
studied with difficulty and uncertainty; but what astronomer doubts
that they are constituted much like the other planets, and have passed,
or will pass, through such stages of progress as we find apparent among
those more directly under our observation? While we shall thus find
universality and harmony among all the starry systems, we shall not
find identity; but with the guiding light of demonstrated scientific
principles, we may apply our knowledge as a key to unlock the mysteries
of the most distant stars. The Milky Way will gleam with new meaning,
Sirius, Aldebaran, the Pleiades, will send us messages of fellowship,
and the established sphere of creative energy will have expanded,
with all its wondrous mechanism, to fill the universe. When we see
at night a vast factory building with every window lighted, one
who understands the operation and mechanism essential to the work
of a mill sees not alone the illuminated windows, but the looms
in motion, the flying shuttles, the spindles humming, the wheels
turning, and all the complicated machinery in active operation. And
he can even picture operatives at work in their various avocations,
and the flashing windows, though themselves silent, are the visible
index of the light within which illuminates and makes possible the work
there performed. And so, when thus comprehended, the flaming stars,
but points of light in the archways of the sky, themselves will reveal
to us the wondrous workings within the realm which they illuminate
and warm and vivify. We may also reasonably infer, as will be more
fully explained further on, that there can be no actual basis for the
opinion sometimes expressed, that great, dark, solid orbs--independent
worlds, in fact--are drifting about through space at random, as it
were, like homeless vagabonds. In these sparsely-occupied domains
the head of each household, as in every well-regulated family, has
all its different members gathered around in strict subordination,
to aid in the support of the establishment. No sun no planets; no
planets no sun, is the general statement of the sidereal formula. Like
a sexual duality, the mutually correlated parts constitute a single,
composite, and interdependent whole: one generates, concentrates,
and transmits; the other receives, transforms, and delivers.
Note.--Regarding the absence of oxygen from the sun's atmosphere
we quote the following from Lord Salisbury's very recent address
(see note at end of Chapter I.): "It is a great aggravation of
the mystery which surrounds the question of the elements, that,
among the lines which are absent from the spectrum of the sun,
those of nitrogen and oxygen stand first. Oxygen constitutes the
largest portion of the solid and liquid substances of our planet,
so far as we know it; and nitrogen is very far the predominant
constituent of our atmosphere. If the earth is a detached bit
whirled off the mass of the sun, as cosmogonists love to tell
us, how comes it that in leaving the sun we cleaned him out so
completely of his nitrogen and oxygen that not a trace of these
gases remains behind to be discovered even by the sensitive
vision of the spectroscope?" We shall find that the absence of
oxygen in the solar envelope is a necessary corollary of its
presence in those of the planets. The same is true, possibly, of
nitrogen. Ammoniacal vapors are decomposable into hydrogen and
nitrogen, and hydrocarbon gases into hydrogen and carbon, just
as aqueous vapors are resolvable into hydrogen and oxygen. In the
earlier stages of the earth's development we have abundant evidence
of an atmosphere heavily laden with carbonic vapors, which have
disappeared, to remain stored as fixed carbon, and the oxygen
has also largely disappeared, to constitute the enormous mass of
oxides in the earth's mass, while the nitrogen remains to dilute
the remaining oxygen and constitute the air we breathe. Their
common correlative, hydrogen, intermingled with metallic vapors,
composes the vast atmosphere of the sun.