P402.Tp(path) 14/9/05 3:00 PM Page 1 Advances in Astronomy From the Big Bang in the Solar Systam This page intentionally left blank P402.Tp(path) 14/9/05 3:00 PM Page 2 THE ROYAL SOCIETY Royal Society Series on Advances in Science-Vol. 1 Advances in Astronomy Editor J M T Thompson DERIVED IN PART FROM WORK ORIGINALLY PUBLISHED IN THE PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY, SERIES A (PHIL. TRANS R SOC. A, 360,2649-3004, 2002) Imperial College Press Published by Imperial College Press 57 Shelton Street Covent Garden London WC2H 9HE Distributed by World Scientific Publishing Co. Pte. Ltd. 5 Toh Tuck Link, Singapore 596224 USA office: 27 Warren Street, Suite 401-402, Hackensack, NJ 07601 UK office: 57 Shelton Street, Covent Garden, London WC2H 9HE British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library. ADVANCES IN ASTRONOMY From the Big Bang to the Solar System Copyright © 2005 by Imperial College Press All rights reserved. This book, or parts thereof, may not be reproduced in any form or by any means, electronic or mechanical, including photocopying, recording or any information storage and retrieval system now known or to be invented, without written permission from the Publisher. For photocopying of material in this volume, please pay a copying fee through the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, USA. In this case permission to photocopy is not required from the publisher. ISBN 1-86094-577-5 Printed in Singapore. Magdalene - Advances in Astronomy.pmd1 8/26/2005, 11:11 AM August 15, 2005 9:16 WSPC/Trim Size: 9in x 6in for Review Volume foreword FOREWORD John D. Barrow DAMTP, Centre for Mathematical Sciences, Cambridge University Astronomy is currently experiencing a Golden Age. Its pace of new dis- covery is relentless and its interconnections with other fields continue to multiply in unexpected ways. Once upon a time astronomy was the time- honoured business of looking through a glass darkly, observing nearby stars and planets, tracking the occasional visiting comet, and painstakingly de- veloping a few reddened spectra from distant galaxies. Gradually, the as- tronomies of other wavebands opened up by means of the technologies that emerged from work on radar during the second world war. New energetic phenomena were discovered that challenged theorists to understand what went on in very strong gravitational fields where matter behaved in ways that could never be duplicated in terrestrial laboratories. Astro-physics be- came a fully fledged subject. Most recently we have seen it become wedded to the world of elementary-particle physics, as cosmologists seek to explain many of the universe’s most mysterious properties by appeal to the high- energy physical processes in the Big Bang. And, by the same token, particle physicists have realised that the extreme environment of the early universe offers them a ‘theoretical laboratory’ in which to test their theories without the slow and expensive construction of huge accelerators. In recent years we have seen the development of three strands of activity which you will see reflected in the articles in this volume: theory and ob- servation have been joined by the specialism of numerical simulation. The rapid growth in computational capability has opened up the possibility of simulating the behaviour of complicated situations, like the formation of stars or planets, so that we can watch what transpires when equations too complex for exact solution are allowed to run their course. What emerges from the use of this new research tool not only challenges astronomers but v August 15, 2005 9:16 WSPC/Trim Size: 9in x 6in for Review Volume foreword vi J. D. Barrow also the traditional ways of publishing the results of research. Researchers now want to publish film or huge numbers of colour images that cannot be handled by traditional avenues for scientific publication. The steady growth in computer technology has been accompanied by spectacular achievements in engineering and electronics. This has made possible a suite of ground-based and satellite-borne astronomical detectors of exquisite sensitivity. They have enabled us to use astronomy to probe the constancy of the constants of nature with greater accuracy than was ever possible in terrestrial laboratories. They have enabled planetary as- tronomers to detect the tiny orbital wobbles produced by large planets orbiting more than a hundred other stars. They have made possible the detailed microwave mapping of the universal radio noise left over from the hot beginning of the universe and the partial reconstruction of the sequence of events that led to the formation of galaxies. We are also able to test the theory that in its earliest moments the universe underwent a surge of ac- celerated ‘inflationary’ expansion, and attempt to explain why more than seventy per cent of the universe is in the form of a strange ‘dark energy’ of unknown composition and origin. Dark energy is a mystery. We see its gravitational effects, we can measure its density, and reconstruct some of its history; we can understand its status as a sort of zero-point energy of the universe. But what is it and why is it controlling the expansion of the universe today? Gamma-ray astronomy witnesses the fall-out from the largest explosions in the universe. Black holes are not only great cookie monsters in the sky. They can collide with one another and with neutron stars. When they do, huge bursts of high-energy gamma rays result. But we expect other evidence of events when worlds collide. Einstein predicted that gravitational waves should be produced in violent, non-spherical processes. Merging black holes and exploding stars should shake space and time enough to send ripples of gravity undulating throughout the universe. By the time they hit the Earth they will be attenuated to a level that is far smaller than the banging and crashing of earthquakes far away and passing of motorcars next door. But by ingeniously shielding detectors from identifiable forms of local noise the signal from gravitational waves can potentially be discriminated and enhanced. The first gravitational-wave detectors are now taking data, and beginning a long process of honing their sensitivity to a level where they expect the true signals of astronomical violence to be visible. These signals will play a decisive role in testing Einstein’s general theory of relativity at new levels of precision. August 15, 2005 9:16 WSPC/Trim Size: 9in x 6in for Review Volume foreword Foreword vii The study of the solar system has undergone a huge resurgence in the past decade. The interior of the Sun can be probed by studying the pattern of internal vibrations that it supports. Its surface activity presents us with spectacular problems of plasma physics that may hold tantalising clues to the cycles of climate variation on Earth. From the unpredictability of huge solar storms to the predictable ups and downs of sunspot numbers, we know that an understanding of the Sun is vital if we are to unravel the effects of past and present human activity on our climate. We used to wonder whether our Sun was unique in having a system of planets orbiting around it. Now we know that it is not. Planet formation is a generic phenomenon in the Universe. But, so far, we can only see planets larger than the Earth. And with only one exception they are found to be in orbits that are far from circular. By contrast, the planets in our solar system move in orbits that are almost circular. This may not be a coincidence. Circular orbits keep the surface temperatures fairly constant; elliptical orbits inevitably produce temperature changes that may be too extreme for early life to survive. This is a story that is just beginning. Our studies of astro-chemistry allow us to understand what types of molecular self-replication are possible, or even probable, in the Universe. In the dust of the stars we may learn something of the make-up of the material that went to make our solar system and made possible the sequence of events that led 4.6 billion years later to the studies in this volume. August 15, 2005 9:16 WSPC/Trim Size: 9in x 6in for Review Volume foreword viii J. D. Barrow John D. Barrow John D. Barrow was born in London in 1952 and attended Ealing Grammar School. He graduated in Mathematics from Durham University in 1974, re- ceived his doctorate in Astrophysics from Oxford University in 1977 (super- vised by Dennis Sciama), and held positions at the Universities of Oxford and California at Berkeley before taking up a position at the Astronomy Centre, University of Sussex in 1981. He was professor of astronomy and Director of the Astronomy Centre at the University of Sussex until 1999. He is a recipient of the Locker Prize for Astronomy and the 1999 Kelvin Medal of the Royal Glasgow Philosophical Society. He was awarded an hon- orary Doctor of Science degree by the University of Hertfordshire in 1999. He held a Senior 5-year Research Fellowship from the Particle Physics and Astronomy Research Council of the UK in 1994-9. He will hold the Gre- sham Professorship of Astronomy for the period 2003-6. He was elected a Fellow of the Royal Society in 2003. In July 1999 he took up a new appointment as Professor of Mathe- matical Sciences at Cambridge University and Director of the Millennium Mathematics Project, a new initiative to improve the understanding and appreciation of mathematics and its applications amongst young people and the general public.