The Project Gutenberg EBook of The Outline of Science, Vol. 1 (of
4), by
J. Arthur Thomson
This eBook is for the use of
anyone anywhere at no cost and with
almost no restrictions
whatsoever. You may copy it, give it away or
re-use it under
the terms of the Project Gutenberg License included
with this
eBook or online at www.gutenberg.org
Title: The Outline of
Science, Vol. 1 (of 4)
A
Plain Story Simply Told
Author: J. Arthur Thomson
Release
Date: January 22, 2007 [EBook #20417]
Language:
English
Character set encoding: ASCII
*** START OF THIS
PROJECT GUTENBERG EBOOK OUTLINE OF SCIENCE ***
Produced
by Brian Janes, Leonard Johnson and the Online
Distributed
Proofreading Team at http://www.pgdp.net
[Illustration:
THE GREAT SCARLET SOLAR PROMINENCES, WHICH ARE SUCH A
NOTABLE
FEATURE OF THE SOLAR PHENOMENA, ARE IMMENSE OUTBURSTS OF
FLAMING
HYDROGEN RISING SOMETIMES TO A HEIGHT OF 500,000
MILES]
THE
OUTLINE OF SCIENCE
A PLAIN
STORY SIMPLY TOLD
EDITED BY
J. ARTHUR
THOMSON
REGIUS PROFESSOR OF NATURAL HISTORY IN THE
UNIVERSITY
OF ABERDEEN
WITH OVER 800 ILLUSTRATIONS
OF WHICH
ABOUT 40 ARE IN COLOUR
IN FOUR VOLUMES
G.
P. PUTNAM'S SONS
NEW YORK AND LONDON
The Knickerbocker
press
Copyright, 1922
by
G. P. Putnam's
Sons
_First Printing April, 1922
Second Printing
April, 1922
Third Printing April, 1922
Fourth Printing April,
1922
Fifth Printing June, 1922
Sixth Printing June,
1922
Seventh Printing June, 1922
Eighth Printing June,
1922
Ninth Printing August, 1922
Tenth Printing September,
1922
Eleventh Printing Sept., 1922
Twelfth Printing, May,
1924_
Made in the United States of
America
INTRODUCTORY NOTE
By Professor J.
Arthur Thomson
Was it not the great philosopher and
mathematician Leibnitz who said
that the more knowledge advances
the more it becomes possible to
condense it into little books? Now
this "Outline of Science" is
certainly not a little
book, and yet it illustrates part of the meaning
of Leibnitz's
wise saying. For here within reasonable compass there is a
library
of little books--an outline of many sciences.
It will be
profitable to the student in proportion to the discrimination
with
which it is used. For it is not in the least meant to be of
the
nature of an Encyclopaedia, giving condensed and comprehensive
articles
with a big full stop at the end of each. Nor is it a
collection of
"primers," beginning at the very beginning
of each subject and working
methodically onwards. That is not the
idea.
What then is the aim of this book? It is to give the
intelligent
student-citizen, otherwise called "the man in the
street," a bunch of
intellectual keys by which to open doors
which have been hitherto shut
to him, partly because he got no
glimpse of the treasures behind the
doors, and partly because the
portals were made forbidding by an
unnecessary display of
technicalities. Laying aside conventional modes
of treatment and
seeking rather to open up the subject as one might on a
walk with
a friend, the work offers the student what might be called
informal
introductions to the various departments of knowledge. To put
it
in another way, the articles are meant to be clues which the
reader
may follow till he has left his starting point very far
behind. Perhaps
when he has gone far on his own he will not be
ungrateful to the simple
book of "instructions to travellers"
which this "Outline of Science" is
intended to be. The
simple "bibliographies" appended to the various
articles
will be enough to indicate "first books." Each article is
meant
to be an invitation to an intellectual adventure, and the
short lists of
books are merely finger-posts for the beginning of
the journey.
We confess to being greatly encouraged by the
reception that has been
given to the English serial issue of "The
Outline of Science." It has
been very hearty--we might almost
say enthusiastic. For we agree with
Professor John Dewey, that
"the future of our civilisation depends upon
the widening
spread and deepening hold of the scientific habit of mind."
And
we hope that this is what "The Outline of Science" makes
for.
Information is all to the good; interesting information is
better still;
but best of all is the education of the scientific
habit of mind.
Another modern philosopher, Professor L. T.
Hobhouse, has declared that
the evolutionist's mundane goal is
"the mastery by the human mind of the
conditions, internal as
well as external, of its life and growth." Under
the
influence of this conviction "The Outline of Science" has
been
written. For life is not for science, but science for life.
And even
more than science, to our way of thinking, is the
individual development
of the scientific way of looking at things.
Science is our legacy; we
must use it if it is to be our very
own.
CONTENTS
INTRODUCTION
3
I. THE ROMANCE OF THE
HEAVENS
7
The scale of the universe--The solar system--Regions
of
the sun--The surface of the sun--Measuring
the speed of
light--Is the sun dying?--The
planets--Venus--Is there
life on Mars?--Jupiter
and Saturn--The moon--The
mountains of the
moon--Meteors and comets--Millions of
meteorites--A great comet--The stellar universe--The
evolution of stars--The age of stars--The nebular
theory--Spiral nebulae--The birth and death of
stars--The shape of our universe--Astronomical
instruments.
II. THE STORY OF
EVOLUTION
53
The beginning of the earth--Making a home for
life--The
first living creatures--The first
plants--The first
animals--Beginnings of
bodies--Evolution of
sex--Beginning of natural
death--Procession of life
through the
ages--Evolution of land animals--The flying
dragons--The first known bird--Evidences of
evolution--Factors in evolution.
III. ADAPTATIONS TO
ENVIRONMENT
113
The shore of the sea--The open sea--The deep
sea--The
fresh waters--The dry land--The
air.
IV. THE STRUGGLE FOR
EXISTENCE
135
Animal and bird mimicry and disguise--Other kinds
of
elusiveness.
V. THE ASCENT OF
MAN
153
Anatomical proof of man's relationship with a
Simian
stock--Physiological
proof--Embryological proof--Man's
pedigree--Man's arboreal apprenticeship--Tentative
men--Primitive men--Races of mankind--Steps in human
evolution--Factors in human progress.
VI. EVOLUTION GOING
ON
183
Evolutionary prospect for man--The fountain of
change;
variability--Evolution of
plants--Romance of
wheat--Changes in animal
life--Story of the
salmon--Forming new
habits--Experiments in locomotion;
new
devices.
VII. THE DAWN OF
MIND
205
A caution in regard to instinct--A useful
law--Senses of
fishes--The mind of a
minnow--The mind and senses of
amphibians--The
reptilian mind--Mind in
birds--Intelligence
co-operating with instinct--The
mind of the
mammal--Instinctive aptitudes--Power of
association--Why is there not more intelligence?--The
mind of monkeys--Activity for activity's
sake--Imitation--The mind of man--Body and mind.
VIII.
FOUNDATIONS OF THE UNIVERSE
243
The world of atoms--The energy of atoms--The
discovery of
X-rays--The discovery of
radium--The discovery of the
electron--The
electron theory--The structure of the
atom--The
new view of matter--Other new views--The
nature
of electricity--Electric current--The
dynamo--Magnetism--Ether and waves--Light--What the
blue "sky" means--Light without heat--Forms of
energy--What heat is--Substitutes for coal--Dissipation
of energy--What a uniform temperature would
mean--Matter, ether, and Einstein--The tides--Origin of
the moon--The earth slowing down--The day becoming
longer.
ILLUSTRATIONS
FACING
PAGE
THE GREAT SCARLET SOLAR PROMINENCES, WHICH ARE SUCH A
NOTABLE FEATURE OF THE SOLAR PHENOMENA, ARE IMMENSE
OUTBURSTS OF FLAMING HYDROGEN RISING SOMETIMES TO A
HEIGHT
OF 500,000 MILES
_Coloured
Frontispiece_
LAPLACE
10
PROFESSOR J. C.
ADAMS
10
Photo: Royal Astronomical
Society.
PROFESSOR EDDINGTON OF CAMBRIDGE
UNIVERSITY
10
Photo: Elliot & Fry, Ltd.
THE
PLANETS, SHOWING THEIR RELATIVE DISTANCES AND
DIMENSIONS
11
THE MILKY
WAY
14
Photo: Harvard College Observatory.
THE
MOON ENTERING THE SHADOW CAST BY THE EARTH
14
THE GREAT NEBULA IN ANDROMEDA, MESSIER
31
15
From a photograph taken at the Yerkes
Observatory.
DIAGRAM SHOWING THE MAIN LAYERS OF THE
SUN
18
SOLAR PROMINENCES SEEN AT TOTAL SOLAR ECLIPSE, MAY 29,
1919. TAKEN AT SOBRAL, BRAZIL
18
Photo: Royal Observatory, Greenwich.
THE
VISIBLE SURFACE OF THE SUN
19
Photo: Mount Wilson Observatory.
THE
SUN PHOTOGRAPHED IN THE LIGHT OF GLOWING HYDROGEN
19
Photo: Mount Wilson Observatory.
THE
AURORA BOREALIS (_Coloured Illustration_)
20
Reproduced from _The Forces of Nature_
(Messrs. Macmillan)
THE GREAT SUN-SPOT OF JULY 17,
1905
22
Yerkes Observatory.
SOLAR
PROMINENCES
22
From photographs taken at the Yerkes
Observatory.
MARS, OCTOBER 5,
1909
23
Photo: Mount Wilson
Observatory.
JUPITER
23
SATURN, NOVEMBER 19,
1911
23
Photo: Professor E. E. Barnard, Yerkes
Observatory.
THE SPECTROSCOPE, AN INSTRUMENT FOR ANALYSING
LIGHT; IT
PROVIDES MEANS FOR IDENTIFYING SUBSTANCES
(_Coloured
Illustration_)
24
THE
MOON
28
MARS
29
Drawings by Professor Percival Lowell.
THE
MOON, AT NINE AND THREE QUARTER DAYS
29
A MAP OF THE CHIEF PLAINS AND CRATERS OF THE
MOON
32
A DIAGRAM OF A STREAM OF METEORS SHOWING THE EARTH
PASSING
THROUGH
THEM
32
COMET, SEPTEMBER 29,
1908
33
Photo: Royal Observatory, Greenwich.
COMET,
OCTOBER 3, 1908
33
Photo: Royal Observatory,
Greenwich.
TYPICAL
SPECTRA
36
Photo: Harvard College Observatory.
A
NEBULAR REGION SOUTH OF ZETA ORIONIS
37
Photo: Mount Wilson Observatory.
STAR
CLUSTER IN HERCULES
37
Photo: Astrophysical Observatory, Victoria,
British Columbia.
THE GREAT NEBULA IN
ORION
40
Photo: Yerkes Observatory.
GIANT
SPIRAL NEBULA, MARCH 23, 1914
41
Photo: Lick Observatory.
A SPIRAL
NEBULA SEEN EDGE-ON
44
Photo: Mount Wilson Observatory.
100-INCH
TELESCOPE, MOUNT WILSON
45
Photo: H. J. Shepstone.
THE YERKES
40-INCH REFRACTOR
48
THE DOUBLE-SLIDE PLATE-HOLDER ON YERKES 40-INCH
REFRACTING
TELESCOPE
49
Photo: H. J. Shepstone.
MODERN
DIRECT-READING SPECTROSCOPE
49
By A. Hilger, Ltd.
CHARLES
DARWIN
56
Photo: Rischgitz Collection.
LORD
KELVIN
56
Photo: Rischgitz Collection.
A GIANT
SPIRAL NEBULA
57
Photo: Lick Observatory.
METEORITE
WHICH FELL NEAR SCARBOROUGH AND IS NOW TO BE SEEN
IN THE
NATURAL HISTORY MUSEUM
57
Photo: Natural History Museum.
A
LIMESTONE CANYON
60
Reproduced from the Smithsonian Report,
1915.
GEOLOGICAL TREE OF
ANIMALS
61
DIAGRAM OF
AMOEBA
61
A PIECE OF A REEF-BUILDING CORAL, BUILT UP BY A LARGE
COLONY OF SMALL SEA-ANEMONE-LIKE POLYPS, EACH OF WHICH
FORMS FROM THE SALTS OF THE SEA A SKELETON OR SHELL OF
LIME
64
From the Smithsonian Report, 1917.
A
GROUP OF CHALK-FORMING ANIMALS, OR FORAMINIFERA, EACH
ABOUT
THE SIZE OF A VERY SMALL PIN'S HEAD
65
Photo: J. J. Ward, F.E.S.
A COMMON
FORAMINIFER (POLYSTOMELLA) SHOWING THE SHELL IN
THE CENTRE
AND THE OUTFLOWING NETWORK OF LIVING MATTER,
ALONG WHICH
GRANULES ARE CONTINUALLY TRAVELLING, AND BY
WHICH FOOD
PARTICLES ARE ENTANGLED AND DRAWN IN
65
Reproduced by permission of the Natural
History Museum
(after Max Schultze).
A
PLANT-LIKE ANIMAL, OR ZOOPHYTE, CALLED OBELIA
68
Photo: J. J. Ward, F.E.S.
TRYPANOSOMA
GAMBIENSE
69
Reproduced by permission of _The Quart.
Journ. Mic.
Sci._
VOLVOX
69
PROTEROSPONGIA
69
GREEN
HYDRA
72
Photo: J. J. Ward, F.E.S.
DIAGRAM
ILLUSTRATING THE BEGINNING OF INDIVIDUAL LIFE
72
EARTHWORM
72
Photo: J. J. Ward, F.E.S.
GLASS MODEL
OF A SEA-ANEMONE
72
Reproduced from the Smithsonian Report,
1917.
THIS DRAWING SHOWS THE EVOLUTION OF THE BRAIN FROM FISH
TO
MAN
73
OKAPI AND GIRAFFE (_Coloured
Illustration_)
74
DIAGRAM OF A SIMPLE REFLEX ARC IN A BACKBONELESS ANIMAL
LIKE AN EARTHWORM
76
THE YUCCA
MOTH
76
Photo: British Museum (Natural
History).
INCLINED PLANE OF ANIMAL
BEHAVIOUR
76
VENUS'
FLY-TRAP
77
Photo: J. J. Ward, F.E.S.
A SPIDER
SUNNING HER EGGS
77
Reproduced by permission from _The Wonders
of Instinct_ by
J. H. Fabre.
THE HOATZIN
INHABITS BRITISH GUIANA
82
PERIPATUS
83
Photograph, from the British Museum (Natural
History), of a
drawing by Mr. E. Wilson.
ROCK
KANGAROO CARRYING ITS YOUNG IN A POUCH
83
Photo: W. S. Berridge, F.Z.S.
PROFESSOR
THOMAS HENRY HUXLEY (1825-95)
86
Photo: Rischgitz.
BARON CUVIER,
1769-1832
86
AN ILLUSTRATION SHOWING VARIOUS METHODS OF FLYING AND
SWOOPING
87
ANIMALS OF THE CAMBRIAN
PERIOD
90
From Knipe's _Nebula to Man_.
A
TRILOBITE
90
Photo: J. J. Ward, F.E.S.
THE GAMBIAN
MUD-FISH, PROTOPTERUS
91
Photo: British Museum (Natural
History).
THE
ARCHAEOPTERYX
91
After William Leche of Stockholm.
WING
OF A BIRD, SHOWING THE ARRANGEMENT OF THE FEATHERS
91
PICTORIAL REPRESENTATION OF STRATA OF THE EARTH'S CRUST,
WITH SUGGESTIONS OF CHARACTERISTIC FOSSILS (_Coloured
Illustration_)
92
FOSSIL OF A PTERODACTYL OR EXTINCT FLYING
DRAGON
94
Photo: British Museum (Natural
History).
PARIASAURUS: AN EXTINCT VEGETARIAN TRIASSIC
REPTILE
94
From Knipe's _Nebula to Man_.
TRICERATOPS:
A HUGE EXTINCT REPTILE
95
From Knipe's _Nebula to Man_.
THE
DUCKMOLE OR DUCK-BILLED PLATYPUS OF AUSTRALIA
95
Photo: _Daily Mail_.
SKELETON OF AN
EXTINCT FLIGHTLESS TOOTHED BIRD, HESPERORNIS
100
After Marsh.
SIX STAGES IN THE
EVOLUTION OF THE HORSE, SHOWING GRADUAL
INCREASE IN
SIZE
101
After Lull and Matthew.
DIAGRAM
SHOWING SEVEN STAGES IN THE EVOLUTION OF THE
FORE-LIMBS AND
HIND-LIMBS OF THE ANCESTORS OF THE MODERN
HORSE, BEGINNING
WITH THE EARLIEST KNOWN PREDECESSORS OF
THE HORSE AND
CULMINATING WITH THE HORSE OF TO-DAY
104
After Marsh and Lull.
WHAT IS MEANT BY HOMOLOGY?
ESSENTIAL SIMILARITY OF
ARCHITECTURE, THOUGH THE
APPEARANCES MAY BE VERY
DIFFERENT
105
AN EIGHT-ARMED CUTTLEFISH OR OCTOPUS ATTACKING A SMALL
CRAB 116
A COMMON STARFISH,
WHICH HAS LOST THREE ARMS AND IS
REGROWING
THEM
116
After Professor W. C. McIntosh.
THE
PAPER NAUTILUS (ARGONAUTA), AN ANIMAL OF THE OPEN SEA
117
Photo: J. J. Ward, F.E.S.
A PHOTOGRAPH SHOWING A
STARFISH (_Asterias Forreri_) WHICH
HAS CAPTURED A LARGE
FISH
117
TEN-ARMED CUTTLEFISH OR SQUID IN THE ACT OF CAPTURING A
FISH 118
GREENLAND
WHALE
118
MINUTE TRANSPARENT EARLY STAGE OF A
SEA-CUCUMBER
119
AN INTRICATE COLONY OF OPEN-SEA ANIMALS (_Physophora
Hydrostatica_) RELATED TO THE PORTUGUESE MAN-OF-WAR
119
Photo: British Museum (Natural History).
A
SCENE IN THE GREAT DEPTHS
119
SEA-HORSE IN SARGASSO
WEED
120
LARGE MARINE LAMPREYS (_Petromyzon
Marinus_)
120
THE DEEP-SEA FISH _Chiasmodon
Niger_
120
DEEP-SEA
FISHES
120
FLINTY SKELETON OF VENUS' FLOWER BASKET (_Euplectella_),
A
JAPANESE DEEP-SEA
SPONGE
121
EGG DEPOSITORY OF _Semotilus
Atromaculatus_
121
THE BITTERLING (_Rhodeus
Amarus_)
124
WOOLLY OPOSSUM CARRYING HER
FAMILY
124
Photo: W. S. Berridge.
SURINAM TOAD
(_Pipa Americana_) WITH YOUNG ONES HATCHING
OUT OF LITTLE
POCKETS ON HER BACK
125
STORM PETREL OR MOTHER CAREY'S CHICKEN (_Procellaria
Pelagica_)
125
ALBATROSS: A CHARACTERISTIC PELAGIC BIRD OF THE SOUTHERN
SEA
128
THE PRAYING MANTIS (_Mantis
Religiosa_)
138
PROTECTIVE COLORATION: A WINTER SCENE IN NORTH
SCANDINAVIA 138
THE
VARIABLE MONITOR (_Varanus_)
139
Photo: A. A. White.
BANDED KRAIT: A
VERY POISONOUS SNAKE WITH ALTERNATING
YELLOW AND DARK
BANDS
140
Photo: W. S. Berridge, F.Z.S.
THE WARTY
CHAMELEON
140
Photos: W. S. Berridge, F.Z.S.
SEASONAL
COLOUR-CHANGE: SUMMER SCENE IN NORTH SCANDINAVIA
141
PROTECTIVE
RESEMBLANCE
142
Photo: J. J. Ward, F.E.S.
WHEN ONLY
A FEW DAYS OLD, YOUNG BITTERN BEGIN TO STRIKE THE
SAME
ATTITUDE AS THEIR PARENTS, THRUSTING THEIR BILLS
UPWARDS
AND DRAWING THEIR BODIES UP SO THAT THEY RESEMBLE
A BUNCH
OF REEDS
143
PROTECTIVE COLORATION OR CAMOUFLAGING, GIVING ANIMALS A
GARMENT OF INVISIBILITY (_Coloured Illustration_)
144
ANOTHER EXAMPLE OF PROTECTIVE COLORATION (_Coloured
Illustration_)
144
DEAD-LEAF BUTTERFLY (_Kallima Inachis_) FROM
INDIA
146
PROTECTIVE RESEMBLANCE BETWEEN A SMALL SPIDER (_to the
left_) AND AN ANT (_to the right_)
146
THE WASP BEETLE, WHICH, WHEN MOVING AMONGST THE
BRANCHES,
GIVES A WASP-LIKE
IMPRESSION
147
Photo: J. J. Ward, F.E.S.
HERMIT-CRAB
WITH PARTNER SEA-ANEMONES
147
CUCKOO-SPIT
147
Photo: G. P. Duffus.
CHIMPANZEE,
SITTING
156
Photo: New York Zoological
Park.
CHIMPANZEE, ILLUSTRATING WALKING
POWERS
156
Photo: New York Zoological Park.
SURFACE
VIEW OF THE BRAINS OF MAN AND CHIMPANZEE
157
SIDE-VIEW OF CHIMPANZEE'S
HEAD
157
Photo: New York Zoological Park.
PROFILE
VIEW OF HEAD OF PITHECANTHROPUS, THE JAVA APE-MAN,
RECONSTRUCTED FROM THE SKULL-CAP
157
After a model by J. H. McGregor.
THE
FLIPPER OF A WHALE AND THE HAND OF A MAN
157
THE GORILLA, INHABITING THE FOREST TRACT OF THE GABOON
IN
AFRICA (_Coloured
Illustration_)
158
"DARWIN'S POINT" ON HUMAN
EAR
160
PROFESSOR SIR ARTHUR KEITH, M.D., LL.D.,
F.R.S.
161
Photo: J. Russell & Sons.
SKELETONS
OF THE GIBBON, ORANG, CHIMPANZEE, GORILLA, MAN
161
After T. H. Huxley (by permission of
Messrs. Macmillan).
SIDE-VIEW OF SKULL OF MAN AND
GORILLA
164
THE SKULL AND BRAIN-CASE OF PITHECANTHROPUS, THE JAVA
APE-MAN, AS RESTORED BY J. H. MCGREGOR FROM THE SCANTY
REMAINS
164
SUGGESTED GENEALOGICAL TREE OF MAN AND ANTHROPOID
APES
165
THE GIBBON IS LOWER THAN THE OTHER APES AS REGARDS ITS
SKULL AND DENTITION, BUT IT IS HIGHLY SPECIALIZED IN THE
ADAPTATION OF ITS LIMBS TO ARBOREAL LIFE
166
Photo: New York Zoological Park.
THE
ORANG HAS A HIGH ROUNDED SKULL AND A LONG FACE
166
Photo: New York Zoological
Park.
COMPARISONS OF THE SKELETONS OF HORSE AND
MAN
167
Photo: British Museum (Natural History).
A
RECONSTRUCTION OF THE JAVA MAN (_Coloured Illustration_)
168
PROFILE VIEW OF THE HEAD OF PITHECANTHROPUS, THE JAVA
APE-MAN--AN EARLY OFFSHOOT FROM THE MAIN LINE OF MAN'S
ASCENT
170
After a model by J. H. McGregor.
PILTDOWN
SKULL
170
From the reconstruction by J. H.
McGregor.
SAND-PIT AT MAUER, NEAR HEIDELBERG: DISCOVERY SITE
OF THE
JAW OF HEIDELBERG
MAN
171
Reproduced by permission from
Osborn's
_Men of the Old Stone
Age_.
PAINTINGS ON THE ROOF OF THE ALTAMIRA CAVE IN NORTHERN
SPAIN, SHOWING A BISON AND A GALLOPING BOAR (_Coloured
Illustration_)
172
PILTDOWN MAN, PRECEDING NEANDERTHAL MAN, PERHAPS 100,000
TO
150,000 YEARS
AGO
174
After the restoration modelled by J. H.
McGregor.
THE NEANDERTHAL MAN OF LA
CHAPELLE-AUX-SAINTS
175
After the restoration modelled by J. H.
McGregor.
RESTORATION BY A. FORESTIER OF THE RHODESIAN MAN
WHOSE
SKULL WAS DISCOVERED IN
1921
176-177
SIDE VIEW OF A PREHISTORIC HUMAN SKULL DISCOVERED IN
1921
IN BROKEN HILL CAVE, NORTHERN
RHODESIA
178
Photo: British Museum (Natural History).
A
CROMAGNON MAN OR CROMAGNARD, REPRESENTATIVE OF A STRONG
ARTISTIC RACE LIVING IN THE SOUTH OF FRANCE IN THE UPPER
PLEISTOCENE, PERHAPS 25,000 YEARS AGO
178
After the restoration modelled by J. H.
McGregor.
PHOTOGRAPH SHOWING A NARROW PASSAGE IN THE CAVERN
OF
FONT-DE-GAUME ON THE
BEUNE
179
Reproduced by permission from Osborn's
_Men of the Old Stone Age_.
A MAMMOTH DRAWN ON THE WALL OF THE
FONT-DE-GAUME CAVERN
179
A GRAZING BISON, DELICATELY AND CAREFULLY DRAWN,
ENGRAVED
ON A WALL OF THE ALTAMIRA CAVE, NORTHERN
SPAIN
179
PHOTOGRAPH OF A MEDIAN SECTION THROUGH THE SHELL OF THE
PEARLY NAUTILUS
186
PHOTOGRAPH OF THE ENTIRE SHELL OF THE PEARLY
NAUTILUS
186
NAUTILUS
186
SHOEBILL
187
Photo: W. S. Berridge.
THE
WALKING-FISH OR MUD-SKIPPER (_Periophthalmus_), COMMON
AT
THE MOUTHS OF RIVERS IN TROPICAL AFRICA, ASIA, AND
NORTH-WEST AUSTRALIA
190
THE AUSTRALIAN MORE-PORK OR
PODARGUS
190
Photo: _The Times_.
PELICAN'S BILL,
ADAPTED FOR CATCHING AND STORING FISHES
191
SPOONBILL'S BILL, ADAPTED FOR SIFTING THE MUD AND
CATCHING
THE SMALL ANIMALS, E.G. FISHES, CRUSTACEANS,
INSECT
LARVAE, WHICH LIVE
THERE
191
AVOCET'S BILL, ADAPTED FOR A CURIOUS SIDEWAYS SCOOPING
IN
THE SHORE-POOLS AND CATCHING SMALL
ANIMALS
191
HORNBILL'S BILL, ADAPTED FOR EXCAVATING A NEST IN A
TREE,
AND ALSO FOR SEIZING AND BREAKING DIVERSE FORMS OF
FOOD,
FROM MAMMALS TO TORTOISES, FROM ROOTS TO
FRUITS
191
FALCON'S BILL, ADAPTED FOR SEIZING, KILLING, AND TEARING
SMALL MAMMALS AND BIRDS
191
PUFFIN'S BILL, ADAPTED FOR CATCHING SMALL FISHES NEAR
THE
SURFACE OF THE SEA, AND FOR HOLDING THEM WHEN CAUGHT
AND
CARRYING THEM TO THE
NEST
191
LIFE-HISTORY OF A
FROG
192
HIND-LEG OF WHIRLIGIG BEETLE WHICH HAS BECOME
BEAUTIFULLY
MODIFIED FOR AQUATIC
LOCOMOTION
192
Photo: J. J. Ward, F.E.S.
THE BIG
ROBBER-CRAB (_Birgus Latro_), THAT CLIMBS THE
COCONUT PALM
AND BREAKS OFF THE NUTS
193
EARLY LIFE-HISTORY OF THE
SALMON
196
THE SALMON LEAPING AT THE FALL IS A MOST FASCINATING
SPECTACLE 197
DIAGRAM OF THE LIFE-HISTORY OF THE
COMMON EEL (_Anguilla
Vulgaris_)
200
CASSOWARY
201
Photo: Gambier Bolton.
THE KIWI,
ANOTHER FLIGHTLESS BIRD, OF REMARKABLE
APPEARANCE, HABITS,
AND STRUCTURE
201
Photo: Gambier Bolton.
THE
AUSTRALIAN FRILLED LIZARD, WHICH IS AT PRESENT TRYING
TO
BECOME A BIPED
202
A CARPET OF
GOSSAMER
202
THE WATER
SPIDER
203
JACKDAW BALANCING ON A
GATEPOST
208
Photo: O. J. Wilkinson.
TWO OPOSSUMS
FEIGNING DEATH
208
From Ingersoll's _The Wit of the
Wild_.
MALE OF THREE-SPINED STICKLEBACK, MAKING A NEST OF
WATER-WEED, GLUED TOGETHER BY VISCID THREADS SECRETED
FROM
THE KIDNEYS AT THE BREEDING SEASON
209
A FEMALE STICKLEBACK ENTERS THE NEST WHICH THE MALE HAS
MADE, LAYS THE EGGS INSIDE, AND THEN DEPARTS
209
HOMING
PIGEON
212
Photo: Imperial War Museum.
CARRIER
PIGEON
212
Photo: Imperial War Museum.
YELLOW-CROWNED
PENGUIN
213
Photo: James's Press Agency.
PENGUINS
ARE "A PECULIAR PEOPLE"
213
Photo: Cagcombe &
Co.
HARPY-EAGLE
216
Photo: W. S. Berridge.
THE DINGO OR
WILD DOG OF AUSTRALIA, PERHAPS AN INDIGENOUS
WILD SPECIES,
PERHAPS A DOMESTICATED DOG THAT HAS GONE
WILD OR
FERAL
216
Photo: W. S. Berridge, F.Z.S.
WOODPECKER
HAMMERING AT A COTTON-REEL, ATTACHED TO A TREE
217
THE
BEAVER
220
THE THRUSH AT ITS
ANVIL
221
Photo: F. R. Hinkins & Son.
ALSATIAN
WOLF-DOG
226
Photo: Lafayette.
THE POLAR BEAR OF
THE FAR NORTH
227
Photo: W. S. Berridge.
AN ALLIGATOR
"YAWNING" IN EXPECTATION OF FOOD
227
From the Smithsonian Report, 1914.
BABY
ORANG
232
Photo: W. P.
Dando.
ORANG-UTAN
232
Photo: Gambier
Bolton.
CHIMPANZEE
233
Photo: James's Press Agency.
BABY
ORANG-UTAN
233
Photo: James's Press
Agency.
ORANG-UTAN
233
Photo: James's Press Agency.
BABY
CHIMPANZEES
233
Photo: James's Press
Agency.
CHIMPANZEE
238
Photo: W. P. Dando.
YOUNG CHEETAHS,
OR HUNTING LEOPARDS
238
Photo: W. S. Berridge.
COMMON
OTTER
239
Photo: C. Reid.
SIR ERNEST
RUTHERFORD
246
Photo: Elliott & Fry.
J.
CLERK-MAXWELL
246
Photo: Rischgitz Collection.
SIR
WILLIAM CROOKES
247
Photo: Ernest H. Mills.
PROFESSOR
SIR W. H. BRAGG
247
Photo: Photo Press.
COMPARATIVE
SIZES OF MOLECULES
250
INCONCEIVABLE NUMBERS AND INCONCEIVABLY SMALL
PARTICLES
250
WHAT IS A
MILLION?
250
THE BROWNIAN
MOVEMENT
251
A SOAP BUBBLE (_Coloured
Illustration_)
252
Reproduced from _The Forces of Nature_
(Messrs. Macmillan).
DETECTING A SMALL QUANTITY OF
MATTER
254
From _Scientific Ideas of To-day_.
THIS
X-RAY PHOTOGRAPH IS THAT OF A HAND OF A SOLDIER
WOUNDED IN
THE GREAT WAR
254
Reproduced by permission of X-Rays Ltd.
AN X-RAY
PHOTOGRAPH OF A GOLF BALL, REVEALING AN IMPERFECT
CORE
254
Photo: National Physical Laboratory.
A
WONDERFUL X-RAY PHOTOGRAPH
255
Reproduced by permission of X-Rays
Ltd.
ELECTRIC DISCHARGE IN A VACUUM
TUBE
258
THE RELATIVE SIZES OF ATOMS AND
ELECTRONS
258
ELECTRONS STREAMING FROM THE SUN TO THE
EARTH
259
PROFESSOR SIR J. J.
THOMSON
262
ELECTRONS PRODUCED BY PASSAGE OF X-RAYS THROUGH
AIR
262
From the Smithsonian Report,
1915.
MAGNETIC DEFLECTION OF RADIUM
RAYS
263
PROFESSOR R. A. MILLIKAN'S APPARATUS FOR COUNTING
ELECTRONS 263
Reproduced by permission of _Scientific American_.
MAKING THE
INVISIBLE VISIBLE
266
THE THEORY OF
ELECTRONS
267
ARRANGEMENTS OF ATOMS IN A
DIAMOND
267
DISINTEGRATION OF
ATOMS
270
SILK TASSEL
ELECTRIFIED
270
Reproduced by permission from _The Interpretation of
Radium_
(John Murray).
SILK TASSEL
DISCHARGED BY THE RAYS FROM RADIUM
270
A HUGE ELECTRIC
SPARK
271
ELECTRICAL ATTRACTION BETWEEN COMMON
OBJECTS
271
From _Scientific Ideas of To-day_.
AN
ELECTRIC SPARK
274
Photo: Leadbeater.
AN ETHER
DISTURBANCE AROUND AN ELECTRON CURRENT
275
From _Scientific Ideas of
To-day_.
LIGHTNING
278
Photo: H. J. Shepstone.
LIGHT
WAVES
279
THE MAGNETIC CIRCUIT OF AN ELECTRIC
CURRENT
279
THE
MAGNET
279
ROTATING DISC OF SIR ISAAC NEWTON FOR MIXING COLOURS
(_Coloured Illustration_)
280
WAVE
SHAPES
282
THE POWER OF A
MAGNET
282
THE SPEED OF
LIGHT
283
Photo: The Locomotive Publishing Co.,
Ltd.
ROTATING DISC OF SIR ISAAC NEWTON FOR MIXING
COLOURS
283
NIAGARA
FALLS
286
TRANSFORMATION OF
ENERGY
287
Photo: Stephen Cribb.
"BOILING"
A KETTLE ON ICE
287
Photo: Underwood & Underwood.
THE
CAUSE OF TIDES
290
THE AEGIR ON THE
TRENT
290
Photo: G. Brocklehurst.
A BIG SPRING
TIDE, THE AEGIR ON THE TRENT
291
Photo: G. Brocklehurst.
The
Outline of Science
INTRODUCTION
There
is abundant evidence of a widened and deepened interest in
modern
science. How could it be otherwise when we think of the
magnitude and
the eventfulness of recent advances?
But the
interest of the general public would be even greater than it is
if
the makers of new knowledge were more willing to expound
their
discoveries in ways that could be "understanded of the
people." No one
objects very much to technicalities in a game
or on board a yacht, and
they are clearly necessary for terse and
precise scientific description.
It is certain, however, that they
can be reduced to a minimum without
sacrificing accuracy, when the
object in view is to explain "the gist of
the matter."
So this OUTLINE OF SCIENCE is meant for the general reader,
who
lacks both time and opportunity for special study, and yet would
take
an intelligent interest in the progress of science which is
making
the world always new.
The story of the triumphs of
modern science is one of which Man may well
be proud. Science
reads the secret of the distant star and anatomises
the atom;
foretells the date of the comet's return and predicts the
kinds of
chickens that will hatch from a dozen eggs; discovers the laws
of
the wind that bloweth where it listeth and reduces to order
the
disorder of disease. Science is always setting forth on
Columbus
voyages, discovering new worlds and conquering them by
understanding.
For Knowledge means Foresight and Foresight means
Power.
The idea of Evolution has influenced all the sciences,
forcing us to
think of _everything_ as with a history behind it,
for we have travelled
far since Darwin's day. The solar system,
the earth, the mountain
ranges, and the great deeps, the rocks and
crystals, the plants and
animals, man himself and his social
institutions--all must be seen as
the outcome of a long process of
Becoming. There are some eighty-odd
chemical elements on the earth
to-day, and it is now much more than a
suggestion that these are
the outcome of an inorganic evolution, element
giving rise to
element, going back and back to some primeval stuff, from
which
they were all originally derived, infinitely long ago. No idea
has
been so powerful a tool in the fashioning of New Knowledge as
this
simple but profound idea of Evolution, that the present is
the child of
the past and the parent of the future. And with the
picture of a
continuity of evolution from nebula to social systems
comes a promise of
an increasing control--a promise that Man will
become not only a more
accurate student, but a more complete
master of his world.
It is characteristic of modern science
that the whole world is seen to
be more vital than before.
Everywhere there has been a passage from the
static to the
dynamic. Thus the new revelations of the constitution of
matter,
which we owe to the discoveries of men like Professor Sir J.
J.
Thomson, Professor Sir Ernest Rutherford, and Professor
Frederick Soddy,
have shown the very dust to have a complexity and
an activity heretofore
unimagined. Such phrases as "dead"
matter and "inert" matter have gone
by the board.
The
new theory of the atom amounts almost to a new conception of
the
universe. It bids fair to reveal to us many of nature's hidden
secrets.
The atom is no longer the indivisible particle of matter
it was once
understood to be. We know now that there is an atom
within the
atom--that what we thought was elementary can be
dissociated and broken
up. The present-day theories of the atom
and the constitution of matter
are the outcome of the
comparatively recent discovery of such things as
radium, the
X-rays, and the wonderful revelations of such instruments as
the
spectroscope and other highly perfected scientific instruments.
The
advent of the electron theory has thrown a flood of light on
what
before was hidden or only dimly guessed at. It has given us a
new
conception of the framework of the universe. We are beginning
to know
and realise of what matter is made and what electric
phenomena mean. We
can glimpse the vast stores of energy locked up
in matter. The new
knowledge has much to tell us about the origin
and phenomena, not only
of our own planet, but other planets, of
the stars, and the sun. New
light is thrown on the source of the
sun's heat; we can make more than
guesses as to its probable age.
The great question to-day is: is there
_one_ primordial substance
from which all the varying forms of matter
have been evolved?
But
the discovery of electrons is only one of the revolutionary
changes
which give modern science an entrancing interest.
As
in chemistry and physics, so in the science of living creatures
there
have been recent advances that have changed the whole
prospect. A good
instance is afforded by the discovery of the
"hormones," or chemical
messengers, which are produced
by ductless glands, such as the thyroid,
the supra-renal, and the
pituitary, and are distributed throughout the
body by the blood.
The work of physiologists like Professor Starling and
Professor
Bayliss has shown that these chemical messengers regulate what
may
be called the "pace" of the body, and bring about that
regulated
harmony and smoothness of working which we know as
health. It is not too
much to say that the discovery of hormones
has changed the whole of
physiology. Our knowledge of the human
body far surpasses that of the
past generation.
The
persistent patience of microscopists and technical improvements
like
the "ultramicroscope" have greatly increased our
knowledge of the
invisible world of life. To the bacteria of a
past generation have been
added a multitude of microscopic
_animal_ microbes, such as that which
causes Sleeping Sickness.
The life-histories and the weird ways of many
important parasites
have been unravelled; and here again knowledge means
mastery. To a
degree which has almost surpassed expectations there has
been a
revelation of the intricacy of the stones and mortar of the house
of
life, and the microscopic study of germ-cells has
wonderfully
supplemented the epoch-making experimental study of
heredity which began
with Mendel. It goes without saying that no
one can call himself
educated who does not understand the central
and simple ideas of
Mendelism and other new departures in
biology.
The procession of life through the ages and the
factors in the sublime
movement; the peopling of the earth by
plants and animals and the
linking of life to life in subtle
inter-relations, such as those between
flowers and their
insect-visitors; the life-histories of individual
types and the
extraordinary results of the new inquiry called
"experimental
embryology"--these also are among the subjects with which
this
OUTLINE will deal.
The behaviour of animals is another
fascinating study, leading to a
provisional picture of the dawn of
mind. Indeed, no branch of science
surpasses in interest that
which deals with the ways and habits--the
truly wonderful devices,
adaptations, and instincts--of insects, birds,
and mammals. We no
longer deny a degree of intelligence to some members
of the animal
world--even the line between intelligence and reason is
sometimes
difficult to find.
Fresh contacts between physiology and the
study of man's mental life;
precise studies of the ways of
children and wild peoples; and new
methods like those of the
psycho-analyst must also receive the attention
they deserve, for
they are giving us a "New Psychology" and the claims
of
psychical research must also be recognised by the open-minded.
The
general aim of the OUTLINE is to give the reader a clear and
concise
view of the essentials of present-day science, so that he
may follow
with intelligence the modern advance and share
appreciatively in man's
continued conquest of his kingdom.
J.
ARTHUR THOMSON.
I
THE ROMANCE OF THE
HEAVENS
THE SCALE OF THE UNIVERSE--THE SOLAR
SYSTEM
Sec. 1
The story of the triumphs of modern
science naturally opens with
Astronomy. The picture of the
Universe which the astronomer offers to us
is imperfect; the lines
he traces are often faint and uncertain. There
are many problems
which have been solved, there are just as many about
which there
is doubt, and notwithstanding our great increase in
knowledge,
there remain just as many which are entirely unsolved.
The problem of the structure and duration of the universe [said
the
great astronomer Simon Newcomb] is the most
far-reaching with which
the mind has to deal.
Its solution may be regarded as the ultimate
object of stellar astronomy, the possibility of reaching which
has
occupied the minds of thinkers since the
beginning of civilisation.
Before our time the
problem could be considered only from the
imaginative or the speculative point of view. Although we can
to-day
attack it to a limited extent by
scientific methods, it must be
admitted that we
have scarcely taken more than the first step toward
the actual solution.... What is the duration of the universe in
time? Is it fitted to last for ever in its present form, or does
it
contain within itself the seeds of
dissolution? Must it, in the
course of time, in
we know not how many millions of ages, be
transformed into something very different from what it now is?
This
question is intimately associated with the
question whether the
stars form a system. If
they do, we may suppose that system to be
permanent in its general features; if not, we must look further
for
our conclusions.
The Heavenly
Bodies
The heavenly bodies fall into two very distinct classes
so far as their
relation to our Earth is concerned; the one class,
a very small one,
comprises a sort of colony of which the Earth is
a member. These bodies
are called _planets_, or wanderers. There
are eight of them, including
the Earth, and they all circle round
the sun. Their names, in the order
of their distance from the sun,
are Mercury, Venus, Earth, Mars,
Jupiter, Saturn, Uranus, Neptune,
and of these Mercury, the nearest to
the sun, is rarely seen by
the naked eye. Uranus is practically
invisible, and Neptune quite
so. These eight planets, together with the
sun, constitute, as we
have said, a sort of little colony; this colony
is called the
Solar System.
The second class of heavenly bodies are those
which lie _outside_ the
solar system. Every one of those
glittering points we see on a starlit
night is at an immensely
greater distance from us than is any member of
the Solar System.
Yet the members of this little colony of ours, judged
by
terrestrial standards, are at enormous distances from one another.
If
a shell were shot in a straight line from one side of Neptune's
orbit to
the other it would take five hundred years to complete
its journey. Yet
this distance, the greatest in the Solar System
as now known (excepting
the far swing of some of the comets), is
insignificant compared to the
distances of the stars. One of the
nearest stars to the earth that we
know of is Alpha Centauri,
estimated to be some twenty-five million
millions of miles away.
Sirius, the brightest star in the firmament, is
double this
distance from the earth.
We must imagine the colony of planets
to which we belong as a compact
little family swimming in an
immense void. At distances which would take
our shell, not
hundreds, but millions of years to traverse, we reach
the
stars--or rather, a star, for the distances between stars are
as
great as the distance between the nearest of them and our Sun.
The
Earth, the planet on which we live, is a mighty globe bounded
by a crust
of rock many miles in thickness; the great volumes of
water which we
call our oceans lie in the deeper hollows of the
crust. Above the
surface an ocean of invisible gas, the
atmosphere, rises to a height of
about three hundred miles,
getting thinner and thinner as it ascends.
[Illustration:
LAPLACE
One of the greatest mathematical astronomers of all
time and the
originator of the nebular theory.]
[Illustration:
_Photo: Royal Astronomical Society._
PROFESSOR J. C.
ADAMS
who, anticipating the great French mathematician, Le
Verrier, discovered
the planet Neptune by calculations based on
the irregularities of the
orbit of Uranus. One of the most
dramatic discoveries in the history of
Science.]
[Illustration:
_Photo: Elliott & Fry, Ltd._
PROFESSOR
EDDINGTON
Professor of Astronomy at Cambridge. The most famous
of the English
disciples of Einstein.]
[Illustration: FIG.
1.--DIAGRAMS OF THE SOLAR SYSTEM
THE COMPARATIVE DISTANCES OF
THE PLANETS
(Drawn approximately to scale)
The
isolation of the Solar System is very great. On the above scale
the
_nearest_ star (at a distance of 25 trillions of miles) would
be over
_one half mile_ away. The hours, days, and years are the
measures of
time as we use them; that is: Jupiter's "Day"
(one rotation of the
planet) is made in ten of _our hours_;
Mercury's "Year" (one revolution
of the planet around
the Sun) is eighty-eight of _our days_. Mercury's
"Day"
and "Year" are the same. This planet turns always the same
side to
the Sun.]
[Illustration: THE COMPARATIVE SIZES OF
THE SUN AND THE PLANETS (Drawn
approximately to scale)
On
this scale the Sun would be 17-1/2 inches in diameter; it is
far
greater than all the planets put together. Jupiter, in turn,
is greater
than all the other planets put together.]
Except
when the winds rise to a high speed, we seem to live in a
very
tranquil world. At night, when the glare of the sun passes
out of our
atmosphere, the stars and planets seem to move across
the heavens with a
stately and solemn slowness. It was one of the
first discoveries of
modern astronomy that this movement is only
apparent. The apparent
creeping of the stars across the heavens at
night is accounted for by
the fact that the earth turns upon its
axis once in every twenty-four
hours. When we remember the size of
the earth we see that this implies a
prodigious speed.
In
addition to this the earth revolves round the sun at a speed of
more
than a thousand miles a minute. Its path round the sun, year
in year
out, measures about 580,000,000 miles. The earth is held
closely to this
path by the gravitational pull of the sun, which
has a mass 333,432
times that of the earth. If at any moment the
sun ceased to exert this
pull the earth would instantly fly off
into space straight in the
direction in which it was moving at the
time, that is to say, at a
tangent. This tendency to fly off at a
tangent is continuous. It is the
balance between it and the sun's
pull which keeps the earth to her
almost circular orbit. In the
same way the seven other planets are held
to their
orbits.
Circling round the earth, in the same way as the earth
circles round the
sun, is our moon. Sometimes the moon passes
directly between us and the
sun, and cuts off the light from us.
We then have a total or partial
eclipse of the sun. At other times
the earth passes directly between the
sun and the moon, and causes
an eclipse of the moon. The great ball of
the earth naturally
trails a mighty shadow across space, and the moon is
"eclipsed"
when it passes into this.
The other seven planets, five of
which have moons of their own, circle
round the sun as the earth
does. The sun's mass is immensely larger than
that of all the
planets put together, and all of them would be drawn
into it and
perish if they did not travel rapidly round it in gigantic
orbits.
So the eight planets, spinning round on their axes, follow
their
fixed paths round the sun. The planets are secondary bodies,
but they
are most important, because they are the only globes in
which there can
be life, as we know life.
If we could be
transported in some magical way to an immense distance in
space
above the sun, we should see our Solar System as it is drawn in
the
accompanying diagram (Fig. 1), except that the planets would be
mere
specks, faintly visible in the light which they receive from
the sun.
(This diagram is drawn approximately to scale.) If we
moved still
farther away, trillions of miles away, the planets
would fade entirely
out of view, and the sun would shrink into a
point of fire, a star. And
here you begin to realize the nature of
the universe. _The sun is a
star. The stars are suns._ Our sun
looks big simply because of its
comparative nearness to us. The
universe is a stupendous collection of
millions of stars or suns,
many of which may have planetary families
like ours.
Sec.
2
The Scale of the Universe
How many stars are there? A
glance at a photograph of star-clouds will
tell at once that it is
quite impossible to count them. The fine
photograph reproduced in
Figure 2 represents a very small patch of that
pale-white belt,
the Milky Way, which spans the sky at night. It is true
that this
is a particularly rich area of the Milky Way, but the entire
belt
of light has been resolved in this way into masses or clouds
of
stars. Astronomers have counted the stars in typical districts
here and
there, and from these partial counts we get some idea of
the total
number of stars. There are estimated to be between two
and three
thousand million stars.
Yet these stars are
separated by inconceivable distances from each
other, and it is
one of the greatest triumphs of modern astronomy to
have mastered,
so far, the scale of the universe. For several centuries
astronomers
have known the relative distances from each other of the sun
and
the planets. If they could discover the actual distance of any
one
planet from any other, they could at once tell all the
distances within
the Solar System.
The sun is, on the
latest measurements, at an average distance of
92,830,000 miles
from the earth, for as the orbit of the earth is not a
true
circle, this distance varies. This means that in six months from
now
the earth will be right at the opposite side of its path round
the
sun, or 185,000,000 miles away from where it is now. Viewed
or
photographed from two positions so wide apart, the nearest
stars show a
tiny "shift" against the background of the
most distant stars, and that
is enough for the mathematician. He
can calculate the distance of any
star near enough to show this
"shift." We have found that the nearest
star to the
earth, a recently discovered star, is twenty-five trillion
miles
away. Only thirty stars are known to be within a hundred
trillion
miles of us.
This way of measuring does not,
however, take us very far away in the
heavens. There are only a
few hundred stars within five hundred trillion
miles of the earth,
and at that distance the "shift" of a star against
the
background (parallax, the astronomer calls it) is so minute
that
figures are very uncertain. At this point the astronomer
takes up a new
method. He learns the different types of stars, and
then he is able to
deduce more or less accurately the distance of
a star of a known type
from its faintness. He, of course, has
instruments for gauging their
light. As a result of twenty years
work in this field, it is now known
that the more distant stars of
the Milky Way are at least a hundred
thousand trillion
(100,000,000,000,000,000) miles away from the sun.
Our sun is
in a more or less central region of the universe, or a few
hundred
trillion miles from the actual centre. The remainder of the
stars,
which are all outside our Solar System, are spread out,
apparently,
in an enormous disc-like collection, so vast that even a ray
of
light, which travels at the rate of 186,000 miles a second,
would
take 50,000 years to travel from one end of it to the other.
This, then
is what we call our universe.
Are there
other Universes?
Why do we say "our universe"? Why
not _the_ universe? It is now believed
by many of our most
distinguished astronomers that our colossal family
of stars is
only one of many universes. By a universe an astronomer
means any
collection of stars which are close enough to control each
other's
movements by gravitation; and it is clear that there might be
many
universes, in this sense, separated from each other by
profound
abysses of space. Probably there are.
For a long
time we have been familiar with certain strange objects in
the
heavens which are called "spiral nebulae" (Fig 4). We shall
see at a
later stage what a nebula is, and we shall see that some
astronomers
regard these spiral nebulae as worlds "in the
making." But some of the
most eminent astronomers believe
that they are separate
universes--"island-universes"
they call them--or great collections of
millions of stars like our
universe. There are certain peculiarities in
the structure of the
Milky Way which lead these astronomers to think
that our universe
may be a spiral nebula, and that the other spiral
nebulae are
"other universes."
[Illustration: _Photo: Harvard
College Observatory._
FIG. 2.--THE MILKY WAY
Note the
cloud-like effect.]
[Illustration: FIG. 3--THE MOON ENTERING
THE SHADOW CAST BY THE EARTH
The diagram shows the Moon
partially eclipsed.]
[Illustration: _From a photograph taken
at the Yerkes Observatory_
FIG. 4.--THE GREAT NEBULA IN
ANDROMEDA, MESSIER 31]
Vast as is the Solar System, then, it
is excessively minute in
comparison with the Stellar System, the
universe of the Stars, which is
on a scale far transcending
anything the human mind can apprehend.
THE SOLAR
SYSTEM
THE SUN
Sec. 1
But now let us turn to
the Solar System, and consider the members of our
own little
colony.
Within the Solar System there are a large number of
problems that
interest us. What is the size, mass, and distance of
each of the
planets? What satellites, like our Moon, do they
possess? What are their
temperatures? And those other, sporadic
members of our system, comets
and meteors, what are they? What are
their movements? How do they
originate? And the Sun itself, what
is its composition, what is the
source of its heat, how did it
originate? Is it running down?
These last questions introduce
us to a branch of astronomy which is
concerned with the physical
constitution of the stars, a study which,
not so very many years
ago, may well have appeared inconceivable. But
the spectroscope
enables us to answer even these questions, and the
answer opens up
questions of yet greater interest. We find that the
stars can be
arranged in an order of development--that there are stars
at all
stages of their life-history. The main lines of the evolution of
the
stellar universe can be worked out. In the sun and stars we
have
furnaces with temperatures enormously high; it is in such
conditions
that substances are resolved into their simplest forms,
and it is thus
we are enabled to obtain a knowledge of the most
primitive forms of
matter. It is in this direction that the
spectroscope (which we shall
refer to immediately) has helped us
so much. It is to this wonderful
instrument that we owe our
knowledge of the composition of the sun and
stars, as we shall
see.
"That the spectroscope will
detect the millionth of a milligram of
matter,
and on that account has discovered new elements, commands
our admiration; but when we find in addition that it will detect
the
nature of forms of matter trillions of
miles away, and moreover,
that it will measure
the velocities with which these forms of matter
are moving with an absurdly small per cent. of possible error, we
can easily acquiesce in the statement that it is the greatest
instrument ever devised by the brain and hand of man."
Such
are some of the questions with which modern astronomy deals.
To
answer them requires the employment of instruments of almost
incredible
refinement and exactitude and also the full resources
of mathematical
genius. Whether astronomy be judged from the point
of view of the
phenomena studied, the vast masses, the immense
distances, the aeons of
time, or whether it be judged as a
monument of human ingenuity,
patience, and the rarest type of
genius, it is certainly one of the
grandest, as it is also one of
the oldest, of the sciences.
The Solar System
In
the Solar System we include all those bodies dependent on the
sun
which circulate round it at various distances, deriving their
light and
heat from the sun--the planets and their moons, certain
comets and a
multitude of meteors: in other words, all bodies
whose movements in
space are determined by the gravitational pull
of the sun.
The Sun
Thanks to our wonderful modern
instruments and the ingenious methods
used by astronomers, we have
to-day a remarkable knowledge of the sun.
Look at the figure
of the sun in the frontispiece. The picture
represents an eclipse
of the sun; the dark body of the moon has screened
the sun's
shining disc and taken the glare out of our eyes; we see a
silvery
halo surrounding the great orb on every side. It is the
sun's
atmosphere, or "crown" (corona), stretching for
millions of miles into
space in the form of a soft silvery-looking
light; probably much of its
light is sunlight reflected from
particles of dust, although the
spectroscope shows an element in
the corona that has not so far been
detected anywhere else in the
universe and which in consequence has been
named Coronium.
We
next notice in the illustration that at the base of the halo
there
are red flames peeping out from the edges of the hidden
disc. When one
remembers that the sun is 866,000 miles in
diameter, one hardly needs to
be told that these flames are really
gigantic. We shall see what they
are presently.
Regions
of the Sun
The astronomer has divided the sun into definite
concentric regions or
layers. These layers envelop the nucleus or
central body of the sun
somewhat as the atmosphere envelops our
earth. It is through these
vapour layers that the bright white
body of the sun is seen. Of the
innermost region, the heart or
nucleus of the sun, we know almost
nothing. The central body or
nucleus is surrounded by a brilliantly
luminous envelope or layer
of vaporous matter which is what we see when
we look at the sun
and which the astronomer calls the photosphere.
Above--that
is, overlying--the photosphere there is a second layer of
glowing
gases, which is known as the reversing layer. This layer is
cooler
than the underlying photosphere; it forms a veil of smoke-like
haze
and is of from 500 to 1,000 miles in thickness.
A third layer
or envelope immediately lying over the last one is the
region
known as the chromosphere. The chromosphere extends from 5,000
to
10,000 miles in thickness--a "sea" of red tumultuous
surging fire.
Chief among the glowing gases is the vapour of
hydrogen. The intense
white heat of the photosphere beneath shines
through this layer,
overpowering its brilliant redness. From the
uppermost portion of the
chromosphere great fiery tongues of
glowing hydrogen and calcium vapour
shoot out for many thousands
of miles, driven outward by some prodigious
expulsive force. It is
these red "prominences" which are such a notable
feature
in the picture of the eclipse of the sun already referred to.
During
the solar eclipse of 1919 one of these red flames rose in less
than
seven hours from a height of 130,000 miles to more than 500,000
miles
above the sun's surface. This immense column of red-hot gas, four
or
five times the thickness of the earth, was soaring upward at the
rate
of 60,000 miles an hour.
These flaming jets or
prominences shooting out from the chromosphere are
not to be seen
every day by the naked eye; the dazzling light of the sun
obscures
them, gigantic as they are. They can be observed, however, by
the
spectroscope any day, and they are visible to us for a very
short
time during an eclipse of the sun. Some extraordinary
outbursts have
been witnessed. Thus the late Professor Young
described one on September
7, 1871, when he had been examining a
prominence by the spectroscope:
It had
remained unchanged since noon of the previous day--a long,
low, quiet-looking cloud, not very dense, or brilliant, or in any
way remarkable except for its size. At 12:30 p.m. the Professor
left
the spectroscope for a short time, and on
returning half an hour
later to his
observations, he was astonished to find the gigantic
Sun flame shattered to pieces. The solar atmosphere was filled
with
flying debris, and some of these portions
reached a height of
100,000 miles above the
solar surface. Moving with a velocity which,
even at the distance of 93,000,000 miles, was almost perceptible
to
the eye, these fragments doubled their
height in ten minutes. On
January 30, 1885,
another distinguished solar observer, the late
Professor Tacchini of Rome, observed one of the greatest
prominences
ever seen by man. Its height was no
less than 142,000
miles--eighteen times the
diameter of the earth. Another mighty
flame was
so vast that supposing the eight large planets of the
solar system ranged one on top of the other, the prominence would
still tower above them.[1]
[1] _The Romance
of Astronomy_, by H. Macpherson.
[Illustration: FIG.
5.--DIAGRAM SHOWING THE MAIN LAYERS OF THE SUN
Compare with
frontispiece.]
[Illustration: _Photo: Royal Observatory,
Greenwich._
FIG. 6.--SOLAR PROMINENCES SEEN AT TOTAL SOLAR
ECLIPSE, May 29, 1919.
TAKEN AT SOBRAL, BRAZIL.
The small
Corona is also visible.]
[Illustration: FIG. 7.--THE VISIBLE
SURFACE OF THE SUN
A photograph taken at the Mount Wilson
Observatory of the Carnegie
Institution at
Washington.]
[Illustration: FIG. 8.--THE SUN
Photographed
in the light of glowing hydrogen, at the Mount Wilson
Observatory
of the Carnegie Institution of Washington: vortex phenomena
near
the spots are especially prominent.]
The fourth and uppermost
layer or region is that of the corona, of
immense extent and
fading away into the surrounding sky--this we have
already
referred to. The diagram (Fig. 5) shows the dispositions of
these
various layers of the sun. It is through these several
transparent
layers that we see the white light body of the
sun.
Sec. 2
The Surface of the Sun
Here let
us return to and see what more we know about the
photosphere--the
sun's surface. It is from the photosphere that we have
gained most
of our knowledge of the composition of the sun, which is
believed
not to be a solid body. Examination of the photosphere shows
that
the outer surface is never at rest. Small bright cloudlets come
and
go in rapid succession, giving the surface, through contrasts
in
luminosity, a granular appearance. Of course, to be visible at
all at
92,830,000 miles the cloudlets cannot be small. They imply
enormous
activity in the photosphere. If we might speak
picturesquely the sun's
surface resembles a boiling ocean of
white-hot metal vapours. We have
to-day a wonderful instrument,
which will be described later, which
dilutes, as it were, the
general glare of the sun, and enables us to
observe these fiery
eruptions at any hour. The "oceans" of red-hot gas
and
white-hot metal vapour at the sun's surface are constantly driven
by
great storms. Some unimaginable energy streams out from the
body or
muscles of th