About 1912, Einstein began a new phase of his gravitational research, with the help of his mathematician friend Marcel Grossmann, by expressing his work in terms of the tensor calculus of Tullio Levi-Civita and Gregorio Ricci-Curbastro . Einstein called his new work the general theory of relativity. He moved from Prague to Zurich in 1912 to take up a chair at the Eidgenössische Technische Hochschule in Zurich. Einstein returned to Germany in 1914 but did not reapply for German citizenship. What he accepted was an impressive offer.
Sa 1873 Geiser ay hihirangin propesor sa Zurich Polytechnikum. Institusyon na ito ay tinatawag na mamaya ang Eidgenössische Technische Hochschule at Geiser ay upang magkaroon ng bilang kasamahan doon, unang Frobenius at pagkatapos ay Hurwitz na napuno Frobenius's chair.