In 1955, an important conference honoring the semi-centennial of special relativity was held in Bern, the Swiss capital city where Einstein was working in the famous patent office during the Annus mirabilis. Rosen attended and gave a talk in which he computed the Einstein pseudotensor and Landau–Lifshitz pseudotensor (two alternative, non-covariant, descriptions of the energy carried by a gravitational field, a notion that is notoriously difficult to pin down in general relativity). These turn out to be zero for the Einstein–Rosen waves, and Rosen argued that this reaffirmed the negative conclusion he had reached with Einstein in 1936.