Speaker Name(s): Laura Parker, B.Sc., Ph.D., Department of Physics and Astronomy, McMaster University, Hamilton Description: Most of the mass in the Universe is believed to be in an unseen form called dark matter. In this talk I will present the observational evidence leading to this incredible realization. I will then focus in particular on the use of gravitational lensing to investigate dark matter. In gravitational lensing light is bent by the presence of massive objects in much the same way that an optical lens bends light. Remarkably, we can use lensing to study the amount and distribution of dark matter in the universe on scales ranging from individual galaxies to the entire universe itself.