From 1913 to 1916 Noether published several papers extending and applying Hilbert’s methods to mathematical objects such as fields of rational functions and the invariants of finite groups. This phase marks the beginning of her engagement with abstract algebra, the field of mathematics to which she would make groundbreaking contributions. In the spring of 1915, Noether was invited to return to the University of Göttingen by David Hilbert and Felix Klein. Their effort to recruit her, however, was blocked by the philologists and historians among the philosophical faculty because they did not believe that woman could do the job. In 1915 David Hilbert invited Noether to join the Göttingen mathematics department, challenging the views of some of his colleagues that a woman should not be allowed to teach at a University. Noether left for Göttingen in late April; two weeks later her mother died suddenly in Erlangen. At about the same time Noether’s father retired and her brother joined the German Army to serve in World War I. Emily then returned to Erlangen to care for her father. During her first years teaching at Göttingen she did not have an official position and was not paid; her family paid for her room and board and supported her academic work. Her lectures often were advertised under Hilbert’s name, and Noether would provide “assistance”. Soon after arriving at Göttingen she demonstrated her capabilities by proving the theorem now known as Noether’s theorem, which shows that a conservation law is associated with any differentiable symmetry of a physical system.