INTRODUCTION

My objective in these five lectures was to introduce the fundamental physical ideas underlying cosmological models of an isotropic hot Big-Bang and the development of large-scale structure in such an expanding universe. My instructions from the Organizing Committee were to assume that the audience had not studied cosmology before, and that is what I have tried to do. My final lecture reviewed a number of results in infrared observational cosmology, but constraints of time and space have not permitted inclusion of that material here.

Much of the material on isotropic cosmological models is developed very well in any number of existing sources (although this is less so for the theory of galaxy formation) and it is with some diffidence that I offer my version. The references list a number of other developments of these topics, and I have borrowed from most of them. Perhaps the best recent text which covers these and many other topics in modern cosmology very thoroughly, and yet very readably, is that by Kolb and Turner (1990). My own research in infrared observational cosmology received an important stimulus from a series of similar lectures presented by Malcolm Longair (1977) over 15 years ago. I hope these lectures might, in a similar way, give young astronomers an introduction which will generate enthusiasm for inventing new infrared observing programs bearing on fundamental cosmological problems.

THE ISOTROPIC UNIVERSE

Introduction

We begin by taking a very large-scale view of the universe, and make a simplicity approximation that the universe is smooth, with no structure. In this approximation we can think of the universe as a fluid (of galaxies) of density ρ, pressure p.