What Do We Observe?
In the previous chapter we introduced and discussed, from the theoretical cosmologist’s vantage point, the fantastic tools astronomers have at their disposal to make observations. Certainly astronomers do not just stare at the sky on a whim, so what do they actually observe? And what do they do with their observations once they are made? We will answer the last question at the end of this chapter. As we will discuss there, cosmologists are less interested in particular images of objects such as stars and galaxies but would like to have maps of the universe, the bigger the better. To make these maps we need to remember that our theory of the universe also informs the observations we make and how we interpret them. In this context in particular it affects the way we measure distances.