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MAN'S PLACE IN THE UNIVERSE
MAN'S PLACE IN THE UNIVERSE
A Study of the Results of Scientific Research in Relation to the Unity or
Plurality of Worlds
BY ALFRED R. WALLACE LL.D., D.C.L., F.R.S., ETC.
'O, glittering host! O, golden line!
I would I had an angel's ken,
Your deepest secrets to divine,
And read your mysteries to men.'
_THIRD EDITION_
LONDON CHAPMAN AND HALL LIMITED 1904
'I said unto my inmost heart,
Shall I don corslet, helm, and shield,
And shall I with a Giant strive,
And charge a Dragon on the field?'
J.H. DELL.
PREFACE
This work has been written in consequence of the great interest excited by
my article, under the same title, which appeared simultaneously in _The
Fortnightly Review_ and the _New York Independent_. Two friends who read
the manuscript were of opinion that a volume, in which the evidence could
be given much more fully, would be desirable, and the result of the
publication of the article confirmed their view.
I was led to a study of the subject when writing four new chapters on
Astronomy for a new edition of _The Wonderful Century_. I then found that
almost all writers on general astronomy, from Sir John Herschel to
Professor Simon Newcomb and Sir Norman Lockyer, stated, as an indisputable
fact, that our sun is situated _in_ the plane of the great ring of the
Milky Way, and also very nearly in the centre of that ring. The most recent
researches also showed that there was little or no proof of there being any
stars or nebulæ very far beyond the Milky Way, which thus seemed to be the
limit, in that direction, of the stellar universe.
Turning to the earth and the other planets of the Solar System, I found
that the most recent researches led to the conclusion that no other planet
was likely to be the seat of organic life, unless perhaps of a very low
type. For many years I had paid special attention to the problem of the
measurement of geological time, and also that of the mild climates and
generally uniform conditions that had prevailed throughout all geological
epochs; and on considering the number of concurrent causes and the delicate
balance of conditions required to maintain such uniformity, I became still
more convinced that the evidence was exceedingly strong against the
probability or possibility of any other planet being inhabited.
Having long been acquainted with most of the works dealing with the
question of the supposed _Plurality of Worlds_, I was quite aware of the
very superficial treatment the subject had received, even in the hands of
the most able writers, and this made me the more willing to set forth the
whole of the available evidence--astronomical, physical, and biological--in
such a way as to show both what was proved and what suggested by it.
The present work is the result, and I venture to think that those who will
read it carefully will admit that it is a book that was worth writing. It
is founded almost entirely on the marvellous body of facts and conclusions
of the New Astronomy together with those reached by modern physicists,
chemists, and biologists. Its novelty consists in combining the various
results of these different branches of science into a connected whole, so
as to show their bearing upon a single problem--a problem which is of very
great interest to ourselves.
This problem is, whether or no the logical inferences to be drawn from the
various results of modern science lend support to the view that our earth
is the only inhabited planet, not only in the Solar System but in the
whole stellar universe. Of course it is a point as to which absolute
demonstration, one way or the other, is impossible. But in the absence of
any direct proofs, it is clearly rational to inquire into probabilities;
and these probabilities must be determined not by our prepossessions for
any particular view, but by an absolutely impartial and unprejudiced
examination of the tendency of the evidence.
As the book is written for the general, educated body of readers, many of
whom may not be acquainted with any aspect of the subject or with the
wonderful advance of recent knowledge in that department often termed the
New Astronomy, a popular account has been given of all those branches of it
which bear upon the special subject here discussed. This part of the work
occupies the first six chapters. Those who are fairly acquainted with
modern astronomical literature, as given in popular works, may begin at my
seventh chapter, which marks the commencement of the considerable body of
evidence and of argument I have been able to adduce.
To those of my readers who may have been influenced by any of the adverse
criticisms on my views as set forth in the article already referred to, I
must again urge, that throughout the whole of this work, neither the facts
nor the more obvious conclusions from the facts are given on my own
authority, but always on that of the best astronomers, mathematicians, and
other men of science to whose works I have had access, and whose names,
with exact references, I generally give.
What I claim to have done is, to have brought together the various facts
and phenomena _they_ have accumulated; to have set forth the hypotheses by
which _they_ account for them, or the results to which the evidence clearly
points; to have judged between conflicting opinions and theories; and
lastly, to have combined the results of the various widely-separated
departments of science, and to have shown how they bear upon the great
problem which I have here endeavoured, in some slight degree, to elucidate.
As such a large body of facts and arguments from distinct sciences have
been here brought together, I have given a rather full summary of the whole
argument, and have stated my final conclusions in six short sentences. I
then briefly discuss the two aspects of the whole problem--those from the
materialistic and from the spiritualistic points of view; and I conclude
with a few general observations on the almost unthinkable problems raised
by ideas of Infinity--problems which some of my critics thought I had
attempted in some degree to deal with, but which, I here point out, are
altogether above and beyond the questions I have discussed, and equally
above and beyond the highest powers of the human intellect.
BROADSTONE, DORSET,
_September_ 1903.
'The wilder'd mind is tost and lost,
O sea, in thy eternal tide;
The reeling brain essays in vain,
O stars, to grasp the vastness wide!
The terrible tremendous scheme
That glimmers in each glancing light,
O night, O stars, too rudely jars
The finite with the infinite!'
J.H. DELL.
CONTENTS
CHAP. PAGE
I. EARLY IDEAS, 1
II. MODERN IDEAS, 7
III. THE NEW ASTRONOMY, 24
IV. THE DISTRIBUTION OF THE STARS, 47
V. DISTANCES OF STARS: THE SUN'S MOTION, 73
VI. UNITY AND EVOLUTION OF THE STAR-SYSTEM, 99
VII. ARE THE STARS INFINITE? 135
VIII. OUR RELATION TO THE MILKY WAY, 156
IX. THE UNIFORMITY OF MATTER AND ITS LAWS, 183
X. THE ESSENTIAL CHARACTERS OF ORGANISMS, 191
XI. PHYSICAL CONDITIONS ESSENTIAL FOR LIFE, 206
XII. THE EARTH IN RELATION TO LIFE, 218
XIII. THE ATMOSPHERE IN RELATION TO LIFE, 243
XIV. THE OTHER PLANETS ARE NOT HABITABLE, 262
XV. THE STARS: HAVE THEY PLANETS? ARE THEY
USEFUL TO US? 282
XVI. STABILITY OF THE STAR-SYSTEM: IMPORTANCE OF
CENTRAL POSITION: SUMMARY AND CONCLUSION, 295
INDEX, 326
_EIGHT DIAGRAMS IN THE TEXT AND TWO STAR CHARTS AT END._
'Who is man, and what his place?
Anxious asks the heart, perplext
In this recklessness of space,
Worlds with worlds thus intermixt:
What has he, this atom creature,
In the infinitude of Nature?'
F.T. PALGRAVE.
MAN'S PLACE IN THE UNIVERSE
CHAPTER I
EARLY IDEAS AS TO THE UNIVERSE AND ITS RELATION TO MAN
When men attained to sufficient intelligence for speculations as to their
own nature and that of the earth on which they lived, they must have been
profoundly impressed by the nightly pageant of the starry heavens. The
intense sparkling brilliancy of Sirius and Vega, the more massive and
steady luminosity of Jupiter and Venus, the strange grouping of the
brighter stars into constellations to which fantastic names indicating
their resemblance to various animals or terrestrial objects seemed
appropriate and were soon generally adopted, together with the apparently
innumerable stars of less and less brilliancy scattered broadcast over the
sky, many only being visible on the clearest nights and to the acutest
vision, constituted altogether a scene of marvellous and impressive
splendour of which it must have seemed almost impossible to attain any real
knowledge, but which afforded an endless field for the imagination of the
observer.
The relation of the stars to the sun and moon in their respective motions
was one of the earliest problems for the astronomer, and it was only
solved by careful and continuous observation, which showed that the
invisibility of the former during the day was wholly due to the blaze of
light, and this is said to have been proved at an early period by the
observed fact that from the bottom of very deep wells stars can be seen
while the sun is shining. During total eclipses of the sun also the
brighter stars become visible, and, taken in connection with the fixity of
position of the pole-star, and the course of those circumpolar stars which
never set in the latitudes of Greece, Egypt, and Chaldea, it soon became
possible to frame a simple hypothesis which supposed the earth to be
suspended in space, while at an unknown distance from it a crystal sphere
revolved upon an axis indicated by the pole-star, and carried with it the
whole host of heavenly bodies. This was the theory of Anaximander (540
B.C.), and it served as the starting-point for the more complex theory
which continued to be held in various forms and with endless modifications
down to the end of the sixteenth century.
It is believed that the early Greeks obtained some knowledge of astronomy
from the Chaldeans, who appear to have been the first systematic observers
of the heavenly bodies by means of instruments, and who are said to have
discovered the cycle of eighteen years and ten days after which the sun and
moon return to the same relative positions as seen from the earth. The
Egyptians perhaps derived their knowledge from the same source, but there
is no proof that they were great observers, and the accurate orientation,
proportions, and angles of the Great Pyramid and its inner passages may
perhaps indicate a Chaldean architect.
The very obvious dependence of the whole life of the earth upon the sun, as
a giver of heat and light, sufficiently explains the origin of the belief
that the latter was a mere appanage of the former; and as the moon also
illuminates the night, while the stars as a whole also give a very
perceptible amount of light, especially in the dry climate and clear
atmosphere of the East, and when compared with the pitchy darkness of
cloudy nights when the moon is below the horizon, it seemed clear that the
whole of these grand luminaries--sun, moon, stars, and planets--were but
parts of the terrestrial system, and existed solely for the benefit of its
inhabitants.
Empedocles (444 B.C.) is said to have been the first who separated the
planets from the fixed stars, by observing their very peculiar motions,
while Pythagoras and his followers determined correctly the order of their
succession from Mercury to Saturn. No attempt was made to explain these
motions till a century later, when Eudoxus of Cnidos, a contemporary of
Plato and of Aristotle, resided for some time in Egypt, where he became a
skilful astronomer. He was the first who systematically worked out and
explained the various motions of the heavenly bodies on the theory of
circular and uniform motion round the earth as a centre, by means of a
series of concentric spheres, each revolving at a different rate and on a
different axis, but so united that all shared in the motion round the polar
axis. The moon, for example, was supposed to be carried by three spheres,
the first revolved parallel to the equator and accounted for the diurnal
motion--the rising and setting--of the moon; another moved parallel to the
ecliptic and explained the monthly changes of the moon; while the third
revolved at the same rate but more obliquely, and explained the inclination
of the moon's orbit to that of the earth. In the same way each of the five
planets had four spheres, two moving like the first two of the moon,
another one also moving in the ecliptic was required to explain the
retrograde motion of the planets, while a fourth oblique to the ecliptic
was needed to explain the diverging motions due to the different obliquity
of the orbit of each planet to that of the earth. This was the celebrated
Ptolemaic system in the simplest form needed to account for the more
obvious motions of the heavenly bodies. But in the course of ages the Greek
and Arabian astronomical observers discovered small divergences due to the
various degrees of excentricity of the orbits of the moon and planets and
their consequent varying rates of motion; and to explain these other
spheres were added, together with smaller circles sometimes revolving
excentrically, so that at length about sixty of these spheres, epicycles
and excentrics were required to account for the various motions observed
with the rude instruments, and the rates of motion determined by the very
imperfect time-measurers of those early ages. And although a few great
philosophers had at different times rejected this cumbrous system and had
endeavoured to promulgate more correct ideas, their views had no influence
on public opinion even among astronomers and mathematicians, and the
Ptolemaic system held full sway down to the time of Copernicus, and was
not finally given up till Kepler's _Laws_ and Galileo's _Dialogues_
compelled the adoption of simpler and more intelligible theories.
We are now so accustomed to look upon the main facts of astronomy as mere
elementary knowledge that it is difficult for us to picture to ourselves
the state of almost complete ignorance which prevailed even among the most
civilised nations throughout antiquity and the Middle Ages. The rotundity
of the earth was held by a few at a very early period, and was fairly well
established in later classical times. The rough determination of the size
of our globe followed soon after; and when instrumental observations became
more perfect, the distance and size of the moon were measured with
sufficient accuracy to show that it was very much smaller than the earth.
But this was the farthest limit of the determination of astronomical sizes
and distances before the discovery of the telescope. Of the sun's real
distance and size nothing was known except that it was much farther from us
and much larger than the moon; but even in the century before the
commencement of the Christian era Posidonius determined the circumference
of the earth to be 240,000 stadia, equal to about 28,600 miles, a
wonderfully close approximation considering the very imperfect data at his
command. He is also said to have calculated the sun's distance, making it
only one-third less than the true amount, but this must have been a chance
coincidence, since he had no means of measuring angles more accurately than
to one degree, whereas in the determination of the sun's distance
instruments are required which measure to a second of arc.
Before the discovery of the telescope the sizes of the planets were quite
unknown, while the most that could be ascertained about the stars was, that
they were at a very great distance from us. This being the extent of the
knowledge of the ancients as to the actual dimensions and constitution of
the visible universe, of which, be it remembered, the earth was held to be
the centre, we cannot be surprised at the almost universal belief that this
universe existed solely for the earth and its inhabitants. In classical
times it was held to be at once the dwelling-place of the gods and their
gift to man, while in Christian ages this belief was but slightly, if at
all, changed; and in both it would have been considered impious to maintain
that the planets and stars did not exist for the service and delight of
mankind alone but in all probability had their own inhabitants, who might
in some cases be even superior in intellect to man himself. But apparently,
during the whole period of which we are now treating, no one was so daring
as even to suggest that there were other worlds with other inhabitants, and
it was no doubt because of the idea that we occupied _the_ world, the very
centre of the whole surrounding universe which existed solely for us, that
the discoveries of Copernicus, Tycho Brahé, Kepler, and Galileo excited so
much antagonism and were held to be impious and altogether incredible. They
seemed to upset the whole accepted order of nature, and to degrade man by
removing his dwelling-place, the earth, from the commanding central
position it had always before occupied.