xii Preface to First Edition
main ideas in cosmology without too much hand-waving. I have tried to avoid the
other extreme, practised by some of my particle physics colleagues, of writing books
on cosmology with the obvious intent of making particle physicists out of every theo-
retical astronomer.
I also do not attempt to teach basic astronomy to physicists. In contrast to astron-
omy scholars, I think the main ideas in cosmology do not require very detailed
knowledge of astrophysics or observational techniques. Whole books have been writ-
ten on distance measurements and the value of the Hubble parameter, which still
remains imprecise to a factor of two. Physicists only need to know that quantities
entering formulae are measurable—albeit incorporating factorsℎto some power—so
that the laws can be discussed meaningfully. At undergraduate level, it is not even
usual to give the errors on measured values.
In most chapters there are subjects demanding such a mastery of theoretical
physics or astrophysics that the explanations have to be qualitative and the derivations
meagre, for instance in general relativity, spontaneous symmetry breaking, inflation
and galaxy formation. This is unavoidable because it just reflects the level of under-
graduates. My intention is to go just a few steps further in these matters than do the
popular monographs.
I am indebted in particular to two colleagues and friends who offered constructive
criticism and made useful suggestions. The particle physicist Professor Kari Enqvist
of NORDITA, Copenhagen, my former student, has gone to the trouble of reading
the whole manuscript. The space astronomer Professor Stuart Bowyer of the Univer-
sity of California, Berkeley, has passed several early mornings of jet lag in Lapland
going through the astronomy-related sections. Anyway, he could not go out skiing
then because it was either a snow storm or− 30 ∘C! Finally, the publisher provided me
with a very knowledgeable and thorough referee, an astrophysicist no doubt, whose
criticism of the chapter on galaxy formation was very valuable to me. For all remain-
ing mistakes I take full responsibility. They may well have been introduced by me
afterwards.
Thanks are also due to friends among the local experts: particle physicist Profes-
sor Masud Chaichian and astronomer Professor Kalevi Mattila have helped me with
details and have answered my questions on several occasions. I am also indebted to
several people who helped me to assemble the pictorial material: Drs Subir Sarkar
in Oxford, Rocky Kolb in the Fermilab, Carlos Frenk in Durham, Werner Kienzle at
CERN and members of the COBE team.
Finally, I must thank my wife Jacqueline for putting up with almost two years of
near absence and full absent-mindedness while writing this book.
Matts Roos