Relativity is one of the most famous scientific theories of the 20th century. But how well does it explain the things we see? In our daily lives. Formulated by Albert Einstein in 1905, the theory of relativity is the notion that the laws of physics are the same everywhere. The theory explains the behavior of objects in space and time, and it can be used to predict everything from the existence of black holes to light bending due to gravity to the behavior of the planet Mercury in its orbit. The theory is deceptively simple. First, there is no absolute frame of reference. Every time you measure an object's velocity or its momentum, or how it experiences time, it's always in relation to something else. Second, the speed of light is the same no matter who measures it or how fast the person measuring it is going. Third, nothing can go faster than light.