Glossary · Vật lý
Length contraction
The decrease in the measured length of an object from its proper length when measured in a reference frame moving with respect to the object.
Proper length is the distance between two points measured by an observer at rest relative to both of them. It is the LONGEST measure; any observer moving relative to the object measures less, following L = L₀ times the square root of (1 minus v²/c²).
The object is not squeezed or deformed. No force acts on it. What changes is the result of a MEASUREMENT made in a different frame — the same kind of statement as time dilation, and caused by the same Lorentz factor.
The contraction occurs only along the direction of motion. Dimensions perpendicular to it are unchanged.