Letter on Relativity

My dear Michele, The general theory of relativity has been completed. I have finally solved the problem of gravitation and planetary motion. The equations are beautiful in their elegance - they show that space and time are not separate entities but form a unified four-dimensional continuum that is curved by the presence of mass and energy. Gravity, as Newton conceived it, does not exist as a force. Rather, massive objects cause spacetime itself to curve, and other objects follow the curvature. The planets orbit the sun not because of some mysterious attractive force, but because they are following the curved geometry of spacetime created by the sun's mass. I have made predictions that can be tested. Light from distant stars passing near the sun should be bent by the sun's gravity - or more accurately, by the curvature of spacetime near the sun. The orbit of Mercury should precess in a way that Newton's equations cannot fully explain, but my equations predict precisely. I am both exhausted and exhilarated. This work has consumed me for nearly a decade. The mathematics was formidable, and I would not have succeeded without the help of my friend Marcel Grossmann and your encouragement. Of course, the world is at war and no one cares about my equations. But someday, when this madness ends, perhaps people will understand that we have glimpsed something fundamental about the nature of the universe. Your friend, Albert