viitekehän

viitekehän is a Finnish term that translates to "reference frame" in English. It is a fundamental concept in physics and mathematics, particularly in the study of motion and coordinate systems. A reference frame is a set of coordinate axes or a system of measurement used to describe the position, velocity, and acceleration of an object. The choice of reference frame can significantly influence how physical phenomena are observed and described.

In classical mechanics, there are two main types of reference frames: inertial and non-inertial. An inertial reference frame is one that is not accelerating. In such a frame, Newton's first law of motion, the law of inertia, holds true: an object at rest will stay at rest, and an object in motion will stay in motion with the same speed and in the same direction unless acted upon by an external force. Conversely, a non-inertial reference frame is one that is accelerating. In a non-inertial frame, apparent forces, such as centrifugal and Coriolis forces, must be introduced to explain the motion of objects, even in the absence of real physical forces.

The concept of reference frames is crucial for understanding relativity. In Einstein's theory of special relativity, the laws of physics are the same for all inertial observers. However, the measurements of time and space can differ between different inertial reference frames. General relativity extends this idea to include accelerating reference frames and gravity, treating gravity not as a force but as a curvature of spacetime. The term viitekehän is thus essential for any discussion involving motion, observation, and the fundamental structure of the universe.