Längenkontrakte

Längenkontrakte is a term used in some sources to refer to the relativistic effect known as length contraction, which describes how the length of an object is measured to be shorter along the direction of motion when observed from a frame moving relative to the object. In standard German physics terminology, the effect is usually called Längenkontraktion, with the plural Längenkontraktionen; Längenkontrakte appears as a less common variant or in older texts.

The effect arises from the Lorentz transformations of special relativity. If an object has a proper length L0, measured in its rest frame, an observer in a frame where the object moves with speed v along the direction of its length measures a length L given by L = L0 / γ, where γ is the Lorentz factor γ = 1 / sqrt(1 − v²/c²). The measurement is defined with simultaneous events in the observer’s frame, which is essential for obtaining the contracted length.

The contraction becomes significant only at high speeds near the speed of light; for everyday speeds γ ≈ 1 and the contraction is negligible. In practice, length contraction is most relevant in high-energy physics and accelerator physics, where particles reach velocities close to c. It is consistent with time dilation and other relativistic effects predicted by the theory.

Common misunderstandings are that objects physically compress themselves in their own frame or that contraction contradicts relativity. In reality, length contraction is a frame-dependent measurement: an object’s length is always measured relative to the observer’s frame.

See also: Längenkontraktion, Lorentz transformation, time dilation.