A civil engineer, scientist and European leader, Jan Wörner has built his career around a conviction: the great scientific and technological challenges exceed the boundaries of institutions as much as those of nations. First a professor and then President of TU Darmstadt, which he helped transform into Germany's first autonomous university, he went on to head the German Aerospace Center (DLR) from 2007 to 2015 before becoming Director General of the European Space Agency from 2015 to 2021. Space gave him an exceptional vantage point on science, technology, international cooperation and the long term. There he argued in particular for an open vision of space exploration and of cooperation between public and private actors. His experience sheds light on a question central to our societies: how do we collectively build infrastructure and ambitions whose results outlast political, economic and national horizons?