Introduction

This chapter is very different from all the others in this book. I have a firmly held conviction that astrophysical cosmology is an observational, if not experimental, science and that the quality of the astrophysics is only as good as the data available to validate cosmological and astrophysical theories. The objective of this chapter is to survey some aspects of the technologies which have enabled astrophysical cosmology to be placed on a firm observational basis. In the telling of this story, we will encounter a number of heroic figures who deserve as much honour, in my view, as the rather better-known theorists and physicists who have played such a startling role in the development of cosmological understanding.

My reason for including this chapter is to bring home to even the most hard-line of theorists the essential role which experimental genius plays in the development of theory. In many ways, this chapter is an attempt to do for cosmology what Peter Galison achieved in his splendid book Image and Logic for particle physics, but at a very much more modest level. Without the imaginative development of novel technology, with which to address the challenges presented by theory, theoretical physics lacks experimental validation.

To oversimplify greatly, the revolution in twentieth-century astrophysics and cosmology can be traced to three great technical developments, which were the heritage of the nineteeth century: (i) the invention of astronomical spectroscopy, (ii) the measurement of the parallaxes, and hence the distances, of stars and (iii) the invention of the photographic process.