Ralph Engel, KIT - Recent progress in understanding ultra-high energy cosmic rays

In this talk I will give a pedagogical introduction to our current understanding the physics of the highest-energy particles of the universe - ultra-high-energy cosmic rays. Focussing on the progress made during the last decade thanks to data of the Pierre Auger Observatory and Telescope Array, observations are discussed in the context of their implications for various physics scenarios and newly emerging questions are highlighted. The talk concludes with a summary of ongoing efforts to upgrade existing cosmic ray detectors and developing new ones with even larger aperture.