The Future of the Universe

188 Pages·2007·0.932 MB·English

by  A.J. Meadows

Astronomers’ Universe
Other titles in this series
Calibrating the Cosmos: How Cosmology Explains Our Big
Bang Universe
Frank Levin
Origins: How the Planets, Stars, Galaxies, and the Universe
Began
Steve Eales
Jack Meadows
The Future of the Universe
A.J. Meadows
Department of Information Studies
Loughborough University
Loughborough
Leics. LE11 3TU
UK
[email protected]
The plates in this book are reproduced courtesy of the U.S. National Aeronautics and Space
Administration (NASA).
Library of Congress Control Number: 2006921441
ISBN-10: 1-85233-946-2
ISBN-13: 978-1-85233-946-3
Printed on acid-free paper.
© Springer-Verlag London Limited 2007
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Contents
Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix
Introduction: To Begin With... . . . . . . . . . . . . . . . . . . . . 1
Us and Them . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Going Places . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1 The Heat of the Sun . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Where the Sun Gets Its Energy . . . . . . . . . . . . . . . . . . . . 10
How the Sun Reached Its Present State . . . . . . . . . . . . . 14
How the Sun Has Changed . . . . . . . . . . . . . . . . . . . . . . 15
The Sun’s Next Stages . . . . . . . . . . . . . . . . . . . . . . . . . . 19
The Sun’s Final Stages . . . . . . . . . . . . . . . . . . . . . . . . . . 24
2 The Mobile Earth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Earthquakes and the Earth’s Interior . . . . . . . . . . . . . . . 29
Changes in the Earth’s Core . . . . . . . . . . . . . . . . . . . . . 33
Changes in the Mantle . . . . . . . . . . . . . . . . . . . . . . . . . 34
Continental Drift and Supercontinents . . . . . . . . . . . . . 37
The Future of the Mobile Earth . . . . . . . . . . . . . . . . . . . 41
3 The Earth’s Oceans and Atmosphere . . . . . . . . . . . . . . . 47
Movements in the Atmosphere . . . . . . . . . . . . . . . . . . . 47
Movements in the Oceans . . . . . . . . . . . . . . . . . . . . . . . 50
Absorbing the Sunlight . . . . . . . . . . . . . . . . . . . . . . . . . 52
The Earth and the Moon . . . . . . . . . . . . . . . . . . . . . . . . 56
Gases in the Atmosphere . . . . . . . . . . . . . . . . . . . . . . . . 58
The Future of the Atmosphere and Oceans . . . . . . . . . . 62
v
vi Contents
4 Magnetic Earth and Magnetic Sun . . . . . . . . . . . . . . . . . 69
The Source of the Earth’s Magnetism . . . . . . . . . . . . . . 69
The Future of the Earth’s Magnetism . . . . . . . . . . . . . . . 72
The Source of the Sun’s Magnetism . . . . . . . . . . . . . . . . 73
The Future of the Sun’s Magnetism . . . . . . . . . . . . . . . . 76
The Solar Wind . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
Losing an Atmosphere . . . . . . . . . . . . . . . . . . . . . . . . . . 79
5 Impact . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
Meteors and Meteorites . . . . . . . . . . . . . . . . . . . . . . . . . 81
Craters on the Moon . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
Impacts on the Earth . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
The Asteroids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
Forecasting Future Impacts . . . . . . . . . . . . . . . . . . . . . . 89
Comets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
6 The Solar System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
The Moon and Mercury . . . . . . . . . . . . . . . . . . . . . . . . . 97
Venus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
Mars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
The Giant Planets and Their Satellites . . . . . . . . . . . . . . 106
7 Our Galaxy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
The Sun’s Path . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
The Sun and Nearby Stars . . . . . . . . . . . . . . . . . . . . . . . 115
Interstellar Matter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117
Supernovae . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120
Spiral Arms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
The Evolving Galaxy . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
And What About Life . . . . . . . . . . . . . . . . . . . . . . . . . . 129
8 Galaxies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
The Galactic Halo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134
The Local Group . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136
Galactic Harassment and Cannibalism . . . . . . . . . . . . . 139
The Galaxy and Dark Matter . . . . . . . . . . . . . . . . . . . . 142
Galaxies and Clusters . . . . . . . . . . . . . . . . . . . . . . . . . . 144
The Virgo Supercluster . . . . . . . . . . . . . . . . . . . . . . . . . 147
Contents vii
9 The Universe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149
Superclusters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149
The Expanding Universe . . . . . . . . . . . . . . . . . . . . . . . . 151
Life in the Universe . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157
But Have We Got It Right? . . . . . . . . . . . . . . . . . . . . . . 160
Further Reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173
Preface
Many excellent books have been written about the past history of
the universe and of the various objects—galaxies, stars, planets—
to be found in it. All the exciting events from the original Big Bang
to the appearance of human beings have been carefully recorded.
Much less has been written about what comes next. What will
happen to all these galaxies, stars, and planets in the future? And
what will happen to us, and to any other intelligent life in the uni-
verse? It is obviously more difficult to examine the future than the
past, but there are ways of doing it. Not everything in the universe
is the same age; so a study of the older objects gives us some idea
of what will happen to the younger objects. Some things vary in a
fairly regular way, so you can guess what will happen next. For
example, the number of spots visible on the Sun’s surface increases
and then decreases again every eleven years on average. These ups
and downs can be expected to continue for a considerable time in
the future. Finally, theoretical explanations of how things work at
present often give some hint of how they will develop in the
future.
One rule-of-thumb in astronomy—though there are plenty of
exceptions—is that the further away objects are, the less we know
about them. This means that it is often more difficult to forecast
the future for distant objects than for ones nearby. For this reason,
the early chapters of the book start with the solar system (espe-
cially the Earth) because we know most about it. The latter part
of the book ventures out further into space to discuss the future
of galaxies and the universe. Of course, what happens in nearby
space is affected by happenings elsewhere: the future of the uni-
verse may well influence the future of the solar system. So some
themes—life in the universe, for example—come up for mention
in more than one chapter.
ix
x Preface
We must never forget that science is always in a state of flux.
Ideas about the world around us have changed greatly over the past
few decades; we must surely expect further significant changes
over the next few decades. Some knowledge—for example, about
how stars evolve—seems firmly based. Other knowledge—for
example, about the expansion of the universe—seems to change
almost from month to month. So the vision of the future presented
here should simply be taken as a best guess based on current
evidence.
To Begin With . . .
Forecasting the future—if only we could! What happened in the
past is interesting, but the really fascinating thing is what may
happen in the future. The problem, of course, is that we know
a fair amount about the past, but little about the future. Yet we
plan our lives on the basis of guesses about what will happen
next. Shall we have a walk tomorrow? It depends on the weather
forecast—that is, the best guess that meteorologists can make
about tomorrow’s weather. Such guesses can be more or less
likely. Will the Sun rise tomorrow? How many people will answer
“no” to that question? Will my local football team win on
Saturday? Well, it all depends: they may have a reasonable chance.
The more complicated the event, the less easy it is to guess what
will happen. But also, the more far away the event in time, the
more difficult it is to guess what will happen. Suppose I ask:
will the Sun rise on a morning a hundred million years from
now? Are you as confident in your reply as you are for a sunrise
tomorrow?
What we are continually doing is using our knowledge of the
past and present to try and predict what will happen in the future.
Meteorologists collect today’s weather data and look at past
weather patterns to try and decide what tomorrow’s weather will
be like. I look at the recent record of my local football club, plus
such things as current injuries to players, to try and guess what
will happen in their next match. How good my guess will be
depends on how good the information I have is, and how well I am
able to use it for prediction. This is as true for predicting the future
of the universe as it is for predicting weather or football results.
In this book, guesses about the future are based on what most
scientists currently regard as our best understanding of the past
and present of the universe. There are two words here that need
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