noether was brought to göttingen in 1915 by david hilbert and felix klein, who wanted her expertise in invariant theory to help them in understanding general relativity, a geometrical theory of gravitation developed mainly by albert einstein. hilbert had observed that the conservation of energy seemed to be violated in general relativity, because gravitational energy could itself gravitate. noether provided the resolution of this paradox, and a fundamental tool of modern theoretical physics, with noether's first theorem, which she proved in 1915, but did not publish until 1918. she not only solved the problem for general relativity, but also determined the conserved quantities for "every" system of physical laws that possesses some continuous symmetry. upon receiving her work, einstein wrote to hilbert: