referanserrammen

Referanserrammen (Norwegian term for reference frame) is a concept in physics describing a coordinate system and an observer relative to which the position and motion of objects are described. A reference frame includes a definition of time and a set of spatial coordinates assigned to events.

In Newtonian mechanics, inertial reference frames move at constant velocity relative to each other, and the laws of mechanics have the same form in all such frames. The Galilean transformation x' = x − vt, t' = t relates coordinates between frames moving with relative velocity v, while time is absolute.

In special relativity, the speed of light is constant in all inertial frames, and coordinates transform via the Lorentz transformation. These shifts produce effects such as the relativity of simultaneity, time dilation, and length contraction, which depend on the observer's frame of reference.

In general relativity, reference frames can be accelerating or influenced by gravitation, and the laws of physics hold locally in freely falling (inertial) frames. Non-inertial frames exhibit fictitious forces, such as centrifugal or Coriolis forces, reflecting the observer's motion relative to spacetime geometry.

Common examples include a car moving relative to the road, a train platform observer, or a rotating planet where a person on the floor experiences centrifugal effects. In experiments, the chosen frame is specified to interpret measurements, and equations are expressed accordingly.

Overall, referanserrammen is central to describing motion, transforming coordinates between observers, and understanding how physical laws apply across different frames.