Wednesday 14 October 2015 Speaker: Chris Pearson (RAL Space Science) Title: "Cosmology 101 : Weighing up the Universe" Abstract: The light that we see in the night sky from stars and galaxies, defines our impression of the Universe. However, when we actually weigh up the stuff in the Universe we find that we have been deceived! Evidence has mounted from the 1930’s to the present day that our Universe contains significantly more matter than is naively revealed by starlight alone. In fact, gravity hints at a matter content as much as six times what we can actually see. This is the elusive Dark Matter that dominates the formation of structure in the Universe. As if that was not embarrassing enough for cosmology, around the turn of the new millennium, there was the shocking discovery of a Dark Energy, that pervades all of space which contains almost three times the content of the matter in the Universe. In this seminar, we shall look at the evidence for Dark Matter and what could it possibly be made of? We shall see how the mysterious dark energy dominates the fate of our Universe.