Extragalactic cosmic-ray propagation
In the last decades significant progress has been made towards understanding the origin and nature of ultra-high-energy cosmic rays (UHECRs). However, their sources and composition still remain largely unknown. To interpret the data and find the elusive sources of UHECRs, it is important to understand how cosmic rays propagate in the universe. This is not a trivial task, given our limited knowledge of extragalactic background photon fields, cosmic magnetic fields, and photonuclear interactions. In this talk I will explore the challenges of modelling the propagation of cosmic rays and discuss the prospects for UHECR astronomy.