At the beginning of 1915, Albert Einstein found himself engaging more and more
in politics; he started to protest the militarism that had plunged Europe into a devastating war. That year also marked a significant change in the path of his long life in science. Collaborating with mathematician Marcel Grossman, Einstein was scrambling to learn all he could about a new kind of geometry, heretofore almost entirely unknown to physicists, that might aid him in characterizing the bending of spacetime. The stakes, he realized, were vast: Could special relativity be generalized into a theory of gravity? Could the Newtonian cosmos of distant inverse-square forces be scrapped in favor of one based on the equivalence of mass and energy with fields of curved space and time? In November 1915, after the most intense intellectual struggle of his life, Einstein was finally able to reveal general relativity to the world. His gargantuan effort was no less than a triumph of theory, reason and abstraction.
This article was originally published with the title Einstein's Compass.