English Issue 19/2025

Eratosthenes was the director of the Library of Alexandria, the greatest treasure trove of knowledge in antiquity. He was probably familiar with ancient Babylonian knowledge, according to which one had to walk day and night for a year in order to circumnavigate the Earth. At 5 kilometers per hour and 120 kilometers per day, we get 40,000 kilometers for a year, which is about right! Instead of relying on this sense of its size, in the 3rd century BC, Eratosthenes calculated the circumference of the Earth using the length of a stick’s shadow and the position of the Sun at various locations. Intuitive knowledge becomes scientific knowledge—that is the path of many insights. In this issue, Ulrich Weger shows that even the idea of our human existence after death moves from religious certainty to scientific certainty.