Local reference frame: Difference between revisions

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In [[theoretical physics]], a '''local reference frame''' ('''local frame''') refers to a [[coordinate system]] or [[frame of reference]] that is only expected to function over a small region or a restricted region of space or [[spacetime]].

The term is most often used in the context of the application of '''local inertial frames''' to small regions of a [[gravitational field]]. Although gravitational [[tidal forces]] will cause the background geometry to become noticeably [[non-Euclidean]] over larger regions, if we restrict ourselves to a sufficiently small region containing a cluster of objects falling together in an ''effectively'' uniform gravitational field, their physics can be described as the physics of that cluster in a space free from explicit background gravitational effects.

==Einstein and general relativity==

When constructing his [[general theory of relativity]], [[Albert Einstein|Einstein]] took the result that an accelerated body feels an apparent gravitational field ([[geeforce]]s), and inverted it: an object in a gravitational field, if it is ''not'' accelerated, will ''not'' be able to detect the existence of the field by making local measurements ("a falling man feels no gravity"). Einstein was then able to complete his general theory by arguing that the physics of curved spacetime must reduce over small regions soto the physics of simple inertial mechanics (in this case [[special relativity]]) for small freefalling regions.

Einstein referred to this as "the happiest idea of my life".