The general principle of relativity as used in Einstein's general theory of relativity is that the laws of physics must take the same form in all reference frames. This is an extension of the special principle of relativity. For other topics related to Einstein see Einstein (disambiguation). ... General relativity (GR) or general relativity theory (GRT) is the theory of gravitation published by Albert Einstein in 1915. ... A frame of reference in physics is a set of axes which enable an observer to measure the aspect, position and motion of all points in a system relative to the reference frame. ... The special principle of relativity is an assumption of Einsteins theory of special relativity that states that the laws of physics must take the same form in all inertial reference frames. ...

Alternative definitions

• The “general principle” was defined by Ernst Mach as the principle that all forms of motion between bodies can be said to be purely relative.

• Modern textbooks tend to define the general principle as being the principle that all relationships between frames of reference can be said to be purely relative.

This change in emphasis from physical “bodies” to more abstract “frames” allows a simpler derivation of a general theory of relativity, avoiding some of the complicating factors that are expected to arise at small scales with real bodies (e.g. quantum mechanics). Ernst Mach Ernst Mach (February 18, 1838 – February 19, 1916) was an Austrian-Czech physicist and philosopher and is the namesake for the Mach number and the optical illusion known as Mach bands. ... Fig. ...