frameindependent

Frame independence, or frame independence, is the property that the description of a physical system or the outcome of a physical law does not depend on the choice of reference frame or coordinate system. It reflects the idea that genuine physical content should be observer-independent.

In classical mechanics, frame independence is encoded in the principle of Galilean invariance: the laws of motion take the same form in all inertial frames related by Galilean transformations. Quantities like position and velocity are frame-dependent, whereas the form of Newton’s laws remains unchanged in appropriate frames.

In special relativity, frame independence is formalized by Lorentz invariance. The laws of physics are the same under Lorentz transformations, and certain quantities are Lorentz invariants. Examples include the spacetime interval and the rest (invariant) mass of particles. These quantities maintain the same value in all inertial frames, even though components such as energy and momentum vary with the observer’s frame.

In general relativity, frame independence is extended to curved spacetime through general covariance: equations are expressed in a coordinate-free, tensor form and hold in any coordinate system. This removes a preferred frame and ensures that physical laws are valid in all spacetimes.

Practical use of frame independence includes distinguishing physical effects from artefacts of a chosen frame, and formulating theories and computations in a way that remains valid under transformations. It is a central organizing principle across physics, mathematics, and related disciplines.