The depths of the night conquer the desert. I am running in total solitude through the vastness of the Sahara. Above me the starry sky and below absolute darkness. Kilometers in front of me and kilometers behind me not a living soul. I don’t see or hear anybody and only the little reflecting flags arranged every 50 meters mark the track in the light of my head lamp. If just one of them turns over or the battery runs out, I will be lost.