The universe has been going through a phase of accelerated expansion for the last 6 billion years. Understanding the origin of this cosmic acceleration is one of the main goals of observational cosmology: is it caused by a cosmological constant or a dynamical dark energy? Or is it a sign that we don’t understand the laws of gravity on cosmological scales?
In this talk I will first describe weak lensing, a powerful observable that helps addressing these fundamental questions. I will then give an overview of the current experimental context for weak lensing. In the main part of the talk, I will present my results on tests of gravity on large scales through weak lensing and end by presenting the Precision Projector Laboratory, which goal is to characterize the new generation of detectors that will be used in future galaxy surveys.