Since the advent of [[theory of relativity|relativity theory]] in the early 1900s, the laws of physics have been written in covariant equations, meaning that they are equally valid in any frame. Heliocentric and geocentric plotting systems are both used today, depending on which allows more convenient calculations. | Since the advent of [[theory of relativity|relativity theory]] in the early 1900s, the laws of physics have been written in covariant equations, meaning that they are equally valid in any frame. Heliocentric and geocentric plotting systems are both used today, depending on which allows more convenient calculations. |