Equations of motion when masses move according to Newton's law of gravity. In general relativity, rotational motion is described by the relativistic angular momentum tensor, including the spin tensor, which enter the equations of motion under covariant derivatives with respect to proper time. The Mathisson–Papapetrou–Dixon equations describe the motion of spinning objects moving in a gravitational field. Unlike the equations of motion for describing particle mechanics, which are systems of coupled ordinary differential equations, the analogous equations governing the dynamics of waves and fields are always partial differential equations, since the waves or fields are functions of space and time. For a particular
Clarke's three laws same time. Clarke's first law was proposed in the 1962 edition of the essay, as "Clarke's Law" in "Profiles of the Future". The second law is offered as a simple observation in the same essay but its status as Clarke's second law was conferred by others. It was initially a derivative of the first law and formally became Clarke's second law where the author proposed the third law in the 1973 revision of "Profiles of the Future," which included an acknowledgement"." It was also here that Clarke wrote about the third law in these words: "As three laws were good