After Albert Einstein published his special theory of relativity in 1905, he spent the next decade trying to come up with a theory of gravity. But for years, he kept running up against a problem. He ...

General Relativity reinterprets the force of gravity not as a traditional force but as a manifestation of the curvature of spacetime. Its formulation rests on a rigorous mathematical framework built ...

Usually, light waves can pass through each other without any resistance. According to the laws of electrodynamics, two light beams can exist in the same place without influencing each other; they ...