The Moon

183 Pages·2018·16.16 MB·English

by  Bill Leatherbarrow

the moon
Kosmos
A series exploring our expanding knowledge
of the cosmos through science and technology
and investigating historical, contemporary
and future developments as well as providing
guidance for all those interested in astronomy.
Series Editor: Peter Morris
Already published:
Jupiter William Sheehan and Thomas Hockey
The Moon Bill Leatherbarrow
The Sun Leon Golub and Jay M. Pasachoff
The Moon
Bill Leatherbarrow

reaktion books
For Alex and Zoe
Published by Reaktion Books Ltd
Unit 32, Waterside
44–48 Wharf Road
London n1 7ux, uk
www.reaktionbooks.co.uk
First published 2018
Copyright © Bill Leatherbarrow 2018
All rights reserved
No part of this publication may be reproduced, stored in a retrieval system, or
transmitted, in any form or by any means, electronic, mechanical, photocopying,
recording or otherwise, without the prior permission of the publishers
Printed and bound in China by 1010 Printing International Ltd
A catalogue record for this book is available from the British Library
isbn 978 1 78023 914 9
contents
Preface 7
1 Our Companion Moon: From Mirror to Museum 9
2 The Moon as a World: Observation and Discovery in
the Telescopic Age 23
3 The Moon in the Modern Age 62
4 The Moon in the Age of Spacecraft Exploration 94
5 Observing the Moon 125

References 167
Further Reading and Resources 172
Acknowledgements 174
Photo Acknowledgements 175
Index 177
The surface of the Moon.
Preface
The aim in writing this book has been not only to provide an
accessible account of current lunar science, but to uncover the
history of observation and discovery that gave rise to that science.
What we know about the Moon today does not exist in isolation, but
has emerged from an unfolding process that has seen awareness of
our satellite pass through various stages and revolutions. We cannot
fully understand our Moon unless we also understand that process
of discovery.
We shall see in the course of the following chapters just how
radically our perception of the Moon has shifted over time as our
knowledge and techniques have improved. Initially an inexplicable,
and at times alarming, presence in our skies – one that gave rise
to all kinds of superstitions and religious beliefs – the Moon then
evolved into an embodiment of our increasing understanding of
celestial mechanics, as we uncovered the mysteries of its movements
and appearances. Subsequently, with the invention of the telescope
it was revealed as another world, one that was perhaps similar to
our own and possibly capable of supporting life. With the advent
of the Space Age that dream was laid aside; our Moon turned out to
be a rocky, airless and uninhabited world, but one that was no less
fascinating. A geologist’s paradise, it provides for those willing to
decipher it a dramatic account of much of our solar system’s history
and an important key to the understanding of worlds elsewhere.
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the moon
That process of discovery is one that can be replicated by the
amateur observer, and this book also sets out to provide practical
guidance for the owner of a small telescope. It is possible to under­
stand our Moon by reading books about it, but nothing brings home
the true meaning of science better than active participation in it.
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one
Our Companion Moon:
From Mirror to Museum
The Moon has always been the most obvious feature in our
night sky. It is our nearest celestial neighbour, at an average
distance of 384,400 km, and with an equatorial diameter of 3,476 km
it subtends an angle of approximately half a degree in the sky, large
enough to display significant detail even to the unaided eye. More­
over, since it describes a regular orbit around the Earth (or, more
accurately, around the common centre of gravity of the Earth–Moon
system) in a period of only 27.3 days, it is more or less a constant
presence in our skies, going through its familiar monthly phases
of New Moon, Half­moon and Full Moon. This period of revolution
is about two days shorter than the 29.5 days that the Moon takes to
complete that cycle of phases (its synodic period, or the time between
successive New Moons). The reason for this is that while the Moon is
revolving around the Earth, the Earth is in turn continuing along its
own orbit around the Sun. So the Moon has to travel that bit farther
each month in order to produce the alignment of Sun, Moon and
Earth that gives rise to New Moon (or indeed any other phase).
Our Moon has drawn observers since the dawn of humankind,
and all have tried to make sense in their own ways of the puzzles it
poses and the questions it raises. What is it? How did it get there?
What should we make of the appearances, or phases, it presents?
Why does it move as it does? What does it mean to humankind,
and what opportunities and threats might it pose?
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