Front matter

Cambridge University Press Fetter Lane, London

Bombay, Calcutta, Madras Toronto Macmillan

Tokyo Maruzen Company, Ltd

Copyrighted in the United States of America by the Macmillan Company

All rights reserved

Lowell Observatory

The Discovery of Pluto

The two photographs were taken at the Lowell Observatory on the nights of March 2 and 5, 1930. The object indicated by arrows was seen to have moved considerably in the interval, and this proved that it was of planetary character.

The bright object in the bottom left-hand corner is the star δ Geminorum (see p. 260).

THE UNIVERSE AROUND US

By SIR JAMES JEANS M.A., D.Sc., Sc.D. LL.D., F.R.S.

CAMBRIDGE AT THE UNIVERSITY PRESS

1930

First Edition, September 1929 Reprinted November 1929 ” January 1930 Second Edition, October 1930

PRINTED IN GREAT BRITAIN

PREFACE

The present book contains a brief account, written in simple language, of the methods and results of modern astronomical research, both observational and theoretical. Special attention has been given to problems of cosmogony and evolution, and to the general structure of the universe. My ideal, perhaps never wholly attainable, has been that of making the entire book intelligible to readers with no special scientific knowledge.

Parts of the book cover the same ground as various lectures I have recently delivered to University and other audiences, including a course of wireless talks I gave last autumn. It has been found necessary to re-write these almost in their entirety, so that very few sentences remain in their original form, but those who have asked me to publish my lectures and wireless talks will find the substance of them in the present book.

J. H. JEANS

DORKING 1 May 1929

PREFACE TO SECOND EDITION

In preparing a second edition, I have taken advantage of a great number of suggestions made by correspondents and reviewers, to whom I offer my sincerest thanks. I have also inserted discussions of the new planet Pluto, the rotation of the galaxy, the apparent expansion of the universe, and other subjects which have become important since the first edition was published, and in general have tried to bring the book up to date.

J. H. JEANS

DORKING 2 August 1930

CONTENTS

PAGE

Introduction—The Study of Astronomy 1

Chapter I Exploring the Sky 16

II Exploring the Atom 92

III Exploring in Time 150

IV Carving out the Universe 194

V Stars 253

VI Beginnings and Endings 325

Index 355

PLATES

The Discovery of Pluto FRONTISPIECE

PLATE FACING PAGE

I The Milky Way in the neighbourhood

of the Southern Cross 23

II Planetary Nebulae:

1. N.G.C. 2022

2. N.G.C. 6720 (The Ring Nebula)

3. N.G.C. 1501

4. N.G.C. 7662 28

III The Nebula in Cygnus 29

IV The Great Nebula M 31 in Andromeda 30

V The Nebula N.G.C. 891 in Andromeda

seen edge-on 31

VI The “Horse’s Head” in the Great Nebula

in Orion 37

VII The Trifid Nebula M 20 in Sagittarius 44

VIII Stellar Spectra 51

IX The Globular Cluster M 13 in Hercules 63

X The Region of ρ Ophiuchi 65

XI Magnification of part of the outer regions

of the Great Nebula M 31 in Andromeda 70

XII Magnification of the central region of the

Great Nebula M 31 in Andromeda 71

XIII The tracks of α- and β-particles 113

XIV Collisions of α-particles with Atoms 117

XV The Nebula N.G.C. 4594 in Virgo

The Nebula N.G.C. 7217 204

XVI A sequence of Nebular Configurations:

1. N.G.C. 3379

2. N.G.C. 4621

3. N.G.C. 3115

4. N.G.C. 4594 in Virgo

5. N.G.C. 4565 in Berenice’s hair 207

XVII The “Whirlpool” Nebula M 51 in

Canes Venatici 210

XVIII The Nebula M 81 in Ursa Major 211

XIX The Nebula M 101 in Ursa Major 212

XX The Nebula M 33 in Triangulum 213

XXI The Lesser and Greater Magellanic Clouds 214

XXII Two Nebulae (N.G.C. 4395, 4401)

suggestive of Tidal Action 236

XXIII The twin Nebulae N.G.C. 4567-8

The Nebula N.G.C. 7479 237

XXIV Saturn and its System of Rings 250