Theodore von Karman Lecture
The past decade has seen the emergence of the so-called "concordance model" of cosmology. In this model, the Universe started about 13.7 billion years ago in a Big Bang and is now dominated by dark matter and dark energy. Together this poorly understood "dark sector" makes up about 95% of the Universe, but the nature of these phenomena remains elusive. Weak gravitational lensing, whereby the observed shapes of background galaxies are slightly distorted by foreground dark matter has proven to be one of the most useful ways to measure dark matter and dark energy. I'll explain the basics of weak lensing and outline some key weak lensing results. Finally, I'll discuss The European Space Agency's Euclid mission. NASA has recently agreed to partner on this ambitious mission to measure the dark sector in the 2020s.