Stock Photo - 22 August 2020, Saxony, Leipzig: Test persons of a large-scale experiment of the University Medicine Halle/Saale are standing at the entrance in front of the Arena Leipzig. Around 2200 visitors take part in the experiment entitled ""Restart-19"", in which pop singer Tim Bendzko will perform. The scientists want to use sensors and other aids to monitor walking paths and fluorescent disinfectant is to make visible which surfaces are often touched. They also want to trace the flight of aerosols - the smallest mixtures of particles that could carry the virus. The aim is to develop a mathematical model with which the risk of a corona outbreak after a major event in a hall can be assessed. Photo: Hendrik Schmidt/dpa-Zentralbild/dpa. - Leipzig/Saxony/Germany