Curiosities of the Sky
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Garrett Serviss >> Curiosities of the Sky
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13 Curiosities of the Sky
by Garrett Serviss
Curiosities of the Sky was first published in 1909 and the text is in
the public domain. The transcription was done by William McClain
(info@sattre-press.com), 2002.
A printed version of this book is available from Sattre Press
(http://csky.sattre-press.com). It includes extensive annotations, a
new introduction and all the original photographs and diagrams.
_________________________________________________________________
Preface
What Froude says of history is true also of astronomy: it is the most
impressive where it transcends explanation. It is not the mathematics
of astronomy, but the wonder and the mystery that seize upon the
imagination. The calculation of an eclipse owes all its prestige to
the sublimity of its data; the operation, in itself, requires no more
mental effort than the preparation of a railway time-table.
The dominion which astronomy has always held over the minds of men is
akin to that of poetry; when the former becomes merely instructive and
the latter purely didactic, both lose their power over the
imagination. Astronomy is known as the oldest of the sciences, and it
will be the longest-lived because it will always have arcana that have
not been penetrated.
Some of the things described in this book are little known to the
average reader, while others are well known; but all possess the
fascination of whatever is strange, marvelous, obscure, or mysterious
-- magnified, in this case, by the portentous scale of the phenomena.
The idea of the author is to tell about these things in plain
language, but with as much scientific accuracy as plain language will
permit, showing the wonder that is in them without getting away from
the facts. Most of them have hitherto been discussed only in technical
form, and in treatises that the general public seldom sees and never
reads.
Among the topics touched upon are:
* The strange unfixedness of the ``fixed stars,'' the vast
migrations of the suns and worlds constituting the universe.
* The slow passing out of existence of those collocations of stars
which for thousands of years have formed famous
``constellations,'' preserving the memory of mythological heroes
and heroines, and perhaps of otherwise unrecorded history.
* The tendency of stars to assemble in immense clouds, swarms, and
clusters.
* The existence in some of the richest regions of the universe of
absolutely black, starless gaps, deeps, or holes, as if one were
looking out of a window into the murkiest night.
* The marvelous phenomena of new, or temporary, stars, which appear
as suddenly as conflagrations, and often turn into something else
as eccentric as themselves.
* The amazing forms of the ``whirlpool,'' ``spiral,'' ``pinwheel,''
and ``lace,'' or ``tress,'' nebulæ.
* The strange surroundings of the sun, only seen in particular
circumstances, but evidently playing a constant part in the daily
phenomena of the solar system.
* The mystery of the Zodiacal Light and the Gegenschein.
* The extraordinary transformations undergone by comets and their
tails.
* The prodigies of meteorites and masses of stone and metal fallen
from the sky.
* The cataclysms that have wrecked the moon.
* The problem of life and intelligence on the planet Mars.
* The problematical origin and fate of the asteroids.
* The strange phenomena of the auroral lights.
An attempt has been made to develop these topics in an orderly way,
showing their connection, so that the reader may obtain a broad
general view of the chief mysteries and problems of astronomy, and an
idea of the immense field of discovery which still lies, almost
unexplored, before it.
The Windows of Absolute Night
To most minds mystery is more fascinating than science. But when
science itself leads straight up to the borders of mystery and there
comes to a dead stop, saying, ``At present I can no longer see my
way,'' the force of the charm is redoubled. On the other hand, the
illimitable is no less potent in mystery than the invisible, whence
the dramatic effect of Keats' ``stout Cortez'' staring at the
boundless Pacific while all his men look at each other with a wild
surmise, ``silent upon a peak in Darien.'' It is with similar feelings
that the astronomer regards certain places where from the peaks of the
universe his vision seems to range out into endless empty space. He
sees there the shore of his little isthmus, and, beyond, unexplored
immensity.
The name, ``coal-sacks,'' given to these strange voids is hardly
descriptive. Rather they produce upon the mind the effect of blank
windows in a lonely house on a pitch-dark night, which, when looked at
from the brilliant interior, become appalling in their rayless murk.
Infinity seems to acquire a new meaning in the presence of these black
openings in the sky, for as one continues to gaze it loses its purely
metaphysical quality and becomes a kind of entity, like the ocean. The
observer is conscious that he can actually see the beginning of its
ebon depths, in which the visible universe appears to float like an
enchanted island, resplendent within with lights and life and gorgeous
spectacles, and encircled with screens of crowded stars, but with its
dazzling vistas ending at the fathomless sea of pure darkness which
encloses all.
The Galaxy, or Milky Way, surrounds the borders of our island in space
like a stellar garland, and when openings appear in it they are, by
contrast, far more impressive than the general darkness of the
interstellar expanse seen in other directions. Yet even that expanse
is not everywhere equally dark, for it contains gloomy deeps
discernable with careful watching. Here, too, contrast plays an
important part, though less striking than within the galactic region.
Some of Sir William Herschel's observations appear to indicate an
association between these tenebrious spots and neighboring star clouds
and nebulæ. It is an illuminating bit of astronomical history that
when he was sweeping the then virgin heavens with his great telescopes
he was accustomed to say to his sister who, note-book in hand, waited
at his side to take down his words, fresh with the inspiration of
discovery: ``Prepare to write; the nebulæ are coming; here space is
vacant.''
The most famous of the ``coal-sacks,'' and the first to be brought to
general attention before astronomers had awakened to the significance
of such things, lies adjacent to the ``Southern Cross,'' and is truly
an amazing phenomenon. It is not alone the conspicuousness of this
celestial vacancy, opening suddenly in the midst of one of the richest
parts of the Galaxy, that has given it its fame, but quite as much the
superstitious awe with which it was regarded by the early explorers of
the South Seas. To them, as well as to those who listened in rapt
wonder to their tales, the ``Coal-sack'' seemed to possess some occult
connection with the mystic ``Cross.'' In the eyes of the sailors it
was not a vacancy so much as a sable reality in the sky, and as,
shuddering, they stared at it, they piously crossed themselves. It was
another of the magical wonders of the unknown South, and as such it
formed the basis of many a ``wild surmise'' and many a sea-dog's yarn.
Scientific investigation has not diminished its prestige, and today no
traveler in the southern hemisphere is indifferent to its fascinating
strangeness, while some find it the most impressive spectacle of the
antarctic heavens.
All around, up to the very edge of the yawning gap, the sheen of the
Milky Way is surpassingly glorious; but there, as if in obedience to
an almighty edict, everything vanishes. A single faint star is visible
within the opening, producing a curious effect upon the sensitive
spectator, like the sight of a tiny islet in the midst of a black,
motionless, waveless tarn. The dimensions of the lagoon of darkness,
which is oval or pear-shaped, are eight degrees by five, so that it
occupies a space in the sky about one hundred and thirty times greater
than the area of the full moon. It attracts attention as soon as the
eye is directed toward the quarter where it exists, and by virtue of
the rarity of such phenomena it appears a far greater wonder than the
drifts of stars that are heaped around it. Now that observatories are
multiplying in the southern hemisphere, the great austral
``Coal-sack'' will, no doubt, receive attention proportioned to its
importance as one of the most significant features of the sky. Already
at the Sydney Observatory photographs have shown that the southern
portion of this Dead Sea of Space is not quite ``bottomless,''
although its northern part defies the longest sounding lines of the
astronomer.
There is a similar, but less perfect, ``coal-sack'' in the northern
hemisphere, in the constellation of ``The Swan,'' which, strange to
say, also contains a well-marked figure of a cross outlined by stars.
This gap lies near the top of the cross-shaped figure. It is best seen
by averted vision, which brings out the contrast with the Milky Way,
which is quite brilliant around it. It does not, however, exercise the
same weird attraction upon the eye as the southern ``Coal-sack,'' for
instead of looking like an absolute void in the sky, it rather appears
as if a canopy of dark gauze had been drawn over the stars. We shall
see the possible significance of this appearance later.
Just above the southern horizon of our northern middle latitudes, in
summer, where the Milky Way breaks up into vast sheets of nebulous
luminosity, lying over and between the constellations Scorpio and
Sagittarius, there is a remarkable assemblage of ``coal-sacks,''
though none is of great size. One of them, near a conspicuous
star-cluster in Scorpio, M80, is interesting for having been the first
of these strange objects noted by Herschel. Probably it was its
nearness to M80 which suggested to his mind the apparent connection of
such vacancies with star-clusters which we have already mentioned.
But the most marvelous of the ``coal-sacks'' are those that have been
found by photography in Sagittarius. One of Barnard's earliest and
most excellent photographs includes two of them, both in the
star-cluster M8. The larger, which is roughly rectangular in outline,
contains one little star, and its smaller neighbor is lune-shaped --
surely a most singular form for such an object. Both are associated
with curious dark lanes running through the clustered stars like
trails in the woods. Along the borders of these lanes the stars are
ranked in parallel rows, and what may be called the bottoms of the
lanes are not entirely dark, but pebbled with faint stellar points.
One of them which skirts the two dark gaps and traverses the cluster
along its greatest diameter is edged with lines of stars, recalling
the alignment of the trees bordering a French highway. This road of
stars cannot be less than many billions of miles in length!
All about the cluster the bed of the Galaxy is strangely disturbed,
and in places nearly denuded, as if its contents had been raked away
to form the immense stack and the smaller accumulations of stars
around it. The well-known ``Trifid Nebula'' is also included in the
field of the photograph, which covers a truly marvelous region, so
intricate in its mingling of nebulæ, star-clusters, star-swarms,
star-streams, and dark vacancies that no description can do it
justice. Yet, chaotic as it appears, there is an unmistakable
suggestion of unity about it, impressing the beholder with the idea
that all the different parts are in some way connected, and have not
been fortuitously thrown together. Miss Agnes M. Clerke made the
striking remark that the dusky lanes in M8 are exemplified on the
largest scale in the great rift dividing the Milky Way, from Cygnus in
the northern hemisphere all the way to the ``Cross'' in the southern.
Similar lanes are found in many other clusters, and they are generally
associated with flanking rows of stars, resembling in their
arrangement the thick-set houses and villas along the roadways that
traverse the approaches to a great city.
But to return to the black gaps. Are they really windows in the
star-walls of the universe? Some of them look rather as if they had
been made by a shell fired through a luminous target, allowing the eye
to range through the hole into the void space beyond. If science is
discretely silent about these things, what can the more venturesome
and less responsible imagination suggest? Would a huge ``runaway
sun,'' like Arcturus, for instance, make such an opening if it should
pass like a projectile through the Milky Way? It is at least a
stimulating inquiry. Being probably many thousands of times more
massive than the galactic stars, such a stellar missile would not be
stopped by them, though its direction of flight might be altered. It
would drag the small stars lying close to its course out of their
spheres, but the ultimate tendency of its attraction would be to sweep
them round in its wake, thus producing rather a star-swarm than a
vacancy. Those that were very close to it might be swept away in its
rush and become its satellites, careering away with it in its flight
into outer space; but those that were farther off, and they would, of
course, greatly outnumber the nearer ones, would tend inward from all
sides toward the line of flight, as dust and leaves collect behind a
speeding motor (though the forces operating would be different), and
would fill up the hole, if hole it were. A swarm thus collected should
be rounded in outline and bordered with a relatively barren ring from
which the stars had been ``sucked'' away. In a general sense the M8
cluster answers to this description, but even if we undertook to
account for its existence by a supposition like the above, the black
gaps would remain unexplained, unless one could make a further draft
on the imagination and suggest that the stars had been thrown into a
vast eddy, or system of eddies, whose vortices appear as dark holes.
Only a maelstrom-like motion could keep such a funnel open, for
without regard to the impulse derived from the projectile, the proper
motions of the stars themselves would tend to fill it. Perhaps some
other cause of the whirling motion may be found. As we shall see when
we come to the spiral nebulæ, gyratory movements are exceedingly
prevalent throughout the universe, and the structure of the Milky Way
is everywhere suggestive of them. But this is hazardous sport even for
the imagination -- to play with suns as if they were but thistle-down
in the wind or corks in a mill-race.
Another question arises: What is the thickness of the hedge of stars
through which the holes penetrate? Is the depth of the openings
proportionate to their width? In other words, is the Milky Way round
in section like a rope, or flat and thin like a ribbon? The answer is
not obvious, for we have little or no information concerning the
relative distances of the faint galactic stars. It would be easier,
certainly, to conceive of openings in a thin belt than in a massive
ring, for in the first case they would resemble mere rifts and breaks,
while in the second they would be like wells or bore-holes. Then, too,
the fact that the Milky Way is not a continuous body but is made up of
stars whose actual distances apart is great, offers another quandary;
persistent and sharply bordered apertures in such an assemblage are a
priori as improbable, if not impossible, as straight, narrow holes
running through a swarm of bees.
The difficulty of these questions indicates one of the reasons why it
has been suggested that the seeming gaps, or many of them, are not
openings at all, but opaque screens cutting off the light from stars
behind them. That this is quite possible in some cases is shown by
Barnard's later photographs, particularly those of the singular region
around the star Rho Ophiuchi. Here are to be seen somber lanes and
patches, apparently forming a connected system which covers an immense
space, and which their discoverer thinks may constitute a ``dark
nebula.'' This seems at first a startling suggestion; but, after all,
why should their not be dark nebulæ as well as visible ones? In truth,
it has troubled some astronomers to explain the luminosity of the
bright nebulæ, since it is not to be supposed that matter in so
diffuse a state can be incandescent through heat, and phosphorescent
light is in itself a mystery. The supposition is also in accord with
what we know of the existence of dark solid bodies in space. Many
bright stars are accompanied by obscure companions, sometimes as
massive as themselves; the planets are non-luminous; the same is true
of meteors before they plunge into the atmosphere and become heated by
friction; and many plausible reasons have been found for believing
that space contains as many obscure as shining bodies of great size.
It is not so difficult, after all, then, to believe that there are
immense collections of shadowy gases and meteoric dust whose presence
is only manifested when they intercept the light coming from shining
bodies behind them.
This would account for the apparent extinguishment of light in open
space, which is indicated by the falling off in relative number of
telescopic stars below the tenth magnitude. Even as things are, the
amount of light coming to us from stars too faint to be seen with the
naked eye is so great that the statement of it generally surprises
persons who are unfamiliar with the inner facts of astronomy. It has
been calculated that on a clear night the total starlight from the
entire celestial sphere amounts to one-sixtieth of the light of the
full moon; but of this less than one-twenty-fifth is due to stars
separately distinguished by the eye. If there were no obscuring medium
in space, it is probable that the amount of starlight would be
noticeably and perhaps enormously increased.
But while it seems certain that some of the obscure spots in the Milky
Way are due to the presence of ``dark nebulæ,'' or concealing veils of
one kind or another, it is equally certain that there are many which
are true apertures, however they may have been formed, and by whatever
forces they may be maintained. These, then, are veritable windows of
the Galaxy, and when looking out of them one is face to face with the
great mystery of infinite space. There the known universe visibly
ends, but manifestly space itself does not end there. It is not within
the power of thought to conceive an end to space, for the instant we
think of a terminal point or line the mind leaps forward to the
beyond. There must be space outside as well as inside. Eternity of
time and infinity of space are ideas that the intellect cannot fully
grasp, but neither can it grasp the idea of a limitation to either
space or time. The metaphysical conceptions of hypergeometry, or
fourth-dimensional space, do not aid us.
Having, then, discovered that the universe is a thing contained in
something indefinitely greater than itself; having looked out of its
windows and found only the gloom of starless night outside -- what
conclusions are we to draw concerning the beyond? It seems as empty as
a vacuum, but is it really so? If it be, then our universe is a single
atom astray in the infinite; it is the only island in an ocean without
shores; it is the one oasis in an illimitable desert. Then the Milky
Way, with its wide-flung garland of stars, is afloat like a tiny
smoke-wreath amid a horror of immeasurable vacancy, or it is an
evanescent and solitary ring of sparkling froth cast up for a moment
on the viewless billows of immensity. From such conclusions the mind
instinctively shrinks. It prefers to think that there is something
beyond, though we cannot see it. Even the universe could not bear to
be alone -- a Crusoe lost in the Cosmos! As the inhabitants of the
most elegant château, with its gardens, parks, and crowds of
attendants, would die of loneliness if they did not know that they
have neighbors, though not seen, and that a living world of indefinite
extent surrounds them, so we, when we perceive that the universe has
limits, wish to feel that it is not solitary; that beyond the hedges
and the hills there are other centers of life and activity. Could
anything be more terrible than the thought of an isolated universe?
The greater the being, the greater the aversion to seclusion. Only the
infinite satisfies; in that alone the mind finds rest.
We are driven, then, to believe that the universal night which
envelopes us is not tenantless; that as we stare out of the
star-framed windows of the Galaxy and see nothing but uniform
blackness, the fault is with our eyes or is due to an obscuring
medium. Since our universe is limited in extent, there must be other
universes beyond it on all sides. Perhaps if we could carry our
telescopes to the verge of the great ``Coal-sack'' near the ``Cross,''
being then on the frontier of our starry system, we could discern,
sparkling afar off in the vast night, some of the outer galaxies. They
may be grander than ours, just as many of the suns surrounding us are
immensely greater than ours. If we could take our stand somewhere in
the midst of immensity and, with vision of infinite reach, look about
us, we should perhaps see a countless number of stellar systems, amid
which ours would be unnoticeable, like a single star among the
multitude glittering in the terrestial sky on a clear night. Some
might be in the form of a wreath, like our own; some might be
globular, like the great star-clusters in Hercules and Centaurus; some
might be glittering circles, or disks, or rings within rings. If we
could enter them we should probably find a vast variety of
composition, including elements unknown to terrestrial chemistry; for
while the visible universe appears to contain few if any substances
not existing on the earth or in the sun, we have no warrant to assume
that others may not exist in infinite space.
And how as to gravitation? We do not know that gravitation acts beyond
the visible universe, but it is reasonable to suppose that it does. At
any rate, if we let go its sustaining hand we are lost, and can only
wander hopelessly in our speculations, like children astray. If the
empire of gravitation is infinite, then the various outer systems must
have some, though measuring by our standards an imperceptible,
attractive influence upon each other, for gravitation never lets go
its hold, however great the space over which it is required to act.
Just as the stars about us are all in motion, so the starry systems
beyond our sight may be in motion, and our system as a whole may be
moving in concert with them. If this be so, then after interminable
ages the aspect of the entire system of systems must change, its
various members assuming new positions with respect to one another. In
the course of time we may even suppose that our universe will approach
relatively close to one of the others; and then, if men are yet living
on the earth, they may glimpse through the openings which reveal
nothing to us now, the lights of another nearing star system, like the
signals of a strange squadron, bringing them the assurance (which can
be but an inference at present) that the ocean of space has other
argosies venturing on its limitless expanse.
There remains the question of the luminiferous ether by whose agency
the waves of light are borne through space. The ether is as mysterious
as gravitation. With regard to ether we only infer its existence from
the effects which we ascribe to it. Evidently the ether must extend as
far as the most distant visible stars. But does it continue on
indefinitely in outer space? If it does, then the invisibility of the
other systems must be due to their distance diminishing the quantity
of light that comes from them below the limit of perceptibility, or to
the interposition of absorbing media; if it does not, then the reason
why we cannot see them is owing to the absence of a means of
conveyance for the light waves, as the lack of an interplanetary
atmosphere prevents us from hearing the thunder of sun-spots. (It is
interesting to recall that Mr Edison was once credited with the
intention to construct a gigantic microphone which should render the
roar of sun-spots audible by transforming the electric vibrations into
sound-waves). On this supposition each starry system would be
enveloped in its own globule of ether, and no light could cross from
one to another. But the probability is that both the ether and
gravitation are ubiquitous, and that all the stellar systems are
immersed in the former like clouds of phosphorescent organisms in the
sea.
So astronomy carries the mind from height to greater height. Men were
long in accepting the proofs of the relative insignificance of the
earth; they were more quickly convinced of the comparative littleness
of the solar system; and now the evidence assails their reason that
what they had regarded as the universe is only one mote gleaming in
the sunbeams of Infinity.
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