Dark Matter in the Universe
What is exciting about Cosmology today is how much we do not know. The observable universe - baryonic matter we are fairly sure comprises only a few percent of the total mass of the universe. The rest is a mystery, but mainstream theories split it between Dark Matter and Dark Energy.
I work at the African Institute of Mathematical Sciences (AIMS), and we are blessed with some great visiting lecturers, and I have followed the courses on Cosmology and Quantum Mechanics with interest.