In 1915, two of the world’s top mathematicians, David Hilbert and Felix Klein, invited Emmy Noether to the University of Göttingen to investigate a puzzle. A problem had cropped up in Albert Einstein’s new theory of gravity, general relativity, which had been unveiled earlier in the year. It seemed that the theory did not adhere to a well-established physical principle known as conservation of energy, which states that energy can change forms but can never be destroyed. Total energy is supposed to remain constant. Noether, a young mathematician with no formal academic appointment, gladly accepted the challenge.
She resolved the issue head-on, showing that energy may not be conserved “locally” — that is, in an arbitrarily small patch of space — but everything works out when the space is sufficiently large. That was one of two theorems she proved that year in Göttingen, Germany. The other theorem, which would ultimately ...
