© Copyright 2011, Jay Alfred
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
written prior permission of the author.
Cover photograph: This shows the visible Earth sitting inside an invisible halo of dark matter particles. The halo
has been given false colours and is not drawn to scale. It serves only for general illustrative purposes and does
not represent the actual halo except in a general way.