Albert Einstein's General Theory of Relativity is possibly the most perfect intellectual achievement in modern physics. Anything that involves gravity, the force that powers everything on the largest, hottest or densest of scales, can be explained by it. From the moment Einstein first proposed the t[...]

At the core of Einstein's general theory of relativity are a set of equations that explain the relationship among gravity, space, and time--possibly the most perfect intellectual achievement of modern physics. For over a century, physicists have been exploring, debating, and at times neglecting Eins[...]