Observations over the past decade seem to have established that the Universe is very peculiar indeed. On the one had, it seems that the amount of mass-energy it contains is very close to the critical amount required to make space flat. On the other hand, it appears that only 4% of this matter is the normal matter with which we are familiar. The rest is "dark matter" (around 30%) which clusters around galaxies, but whose form is unknown, or dark energy (about 70%) which is again very poorly understood, and affects the expansion of the Universe on the very largest scales, driving an accelerating expansion which will eventually make the Universe a very large and lonely place. In this module we will examine the evidence for these strange results. The basic equations which govern the dynamics and curvature of the Universe will be derived, using a Newtonian approximation.
These equations will then be applied to interpret observations, and we will discover how the observed properties of distant objects are affected by the geometry and expansion of the Universe. The evidence for the Hot Big Bang and for dark matter, will be reviewed, and we will chart the way in which the Universe has developed through various evolutionary stages, starting from a very uniform initial state, and leading to the structures we observe today.