What is the Universe Made Of?
If we want to construct a model of the universe we need to know what is in it and we also need to know the physical properties of whatever it is. In this chapter we will therefore have to answer the questions: what stuff, what kinds of matter, is there and where does it come from. Of course we are interested in the “stuff” from the point of view of cosmology and building our cosmological models. This means that we gloss over or even leave out some stuff that is important in other branches of physics.