A little over a hundred years ago, Paul Ehrenfest came to Leiden to conduct research at the university. He wanted to make significant contributions to physics and inspire many people, but he also suffered from severe depression, which eventually cost him his life. Still, it gives me comfort that, after all this time, he is receiving the recognition he deserves. That’s why I was delighted when, during a visit to the Science Library, I opened a book and saw an authentic signature by Ehrenfest himself on the first page.
