Great Idea 8

Idea 8: Einstein’s theory of relativity

    In 1905, Albert Einstein proposed the most revolutionary theoretical innovation in physics, the special theory of relativity. Einstein showed that the laws of physics are the same in all inertial reference frames, and that the speed of light in a vacuum was independent of the motion of all observers. The special theory of relativity introduced a new framework for all of physics and proposed new concepts of space and time. Einstein showed that space, time, and mass are not absolute. Instead, all three vary depending on  speed.  Because speeds are always measured relative to a frame of reference, Einstein’s theory is typically referred to as a theory of relativity.

    The most famous equation in physics, E = mc2, comes from Einstein’s theory of relativity. This equation states that energy equals mass multiplied by the speed of light squared. This means that mass and energy are equivalent and interconvertable.
        Einstein  spent 10 years trying to include acceleration in the theory and published his theory of general relativity in 1915. When Einstein tried to apply accelerating masses to his special theory, he realised objects with mass must somehow influence the surrounding dimensions (space-time) in such a way that the object seems to act as if it can pull on other masses. It's as if matter weighs down the fabric of spacetime it is sitting in, creating a 'curve' that causes other nearby matter to slide towards it. Thus, massive objects cause a distortion in space-time, which is felt as gravity. 

    The mathematical equations of Einstein's general theory of relativity, tested time and time again, are currently the most accurate way to predict gravitational interactions, replacing those developed by Isaac Newton several centuries prior.