Intercluster Magnetic Fields and Ultra High Energy Cosmic Rays

Cosmic rays travel at speeds essentially indistinguishable from the speed of light. However, whilst travelling through magnetic fields, both regular and turbulent, they are delayed behind the light since they are usually charged particles and their paths are not straight lines. Those delays can be so long that they are an impediment to correctly identifying sources, which may be variable in time. The magnitude of such delays will be discussed and compared to the characteristic time variation of possible cosmic ray sources.