# Length Contraction

In physics, length contraction – according to Hendrik Lorentz – is the physical phenomenon of a decrease in length detected by an observer of objects that travel at any non-zero velocity relative to that observer. This contraction (more formally called Lorentz contraction or Lorentz–FitzGerald contraction) is usually only noticeable at a substantial fraction of the speed of light; the contraction is only in the direction parallel to the direction in which the observed body is travelling. This effect is negligible at everyday speeds, and can be ignored for all regular purposes. Only at greater speeds does it become important. At a speed of 13,400,000 m/s (30 million mph, .0447c), the length is 99.9% of the length at rest; at a speed of 42,300,000 m/s (95 million mph, 0.141c), the length is still 99%. As the magnitude of the velocity approaches the speed of light, the effect becomes dominant, as can be seen from the formula:

where

is the proper length (the length of the object in its rest frame),
is the length observed by an observer in relative motion with respect to the object,
is the relative velocity between the observer and the moving object,
is the speed of light,

and the Lorentz factor is defined as

.

In this equation it is assumed that the object is parallel with its line of movement. For the observer in relative movement, the length of the object is measured by subtracting the simultaneously measured distances of both ends of the object. For more general conversions, see the Lorentz transformations. An observer at rest viewing an object travelling very close to the speed of light would observe the length of the object in the direction of motion as very near zero.

Read more about Length Contraction:  History, Basis in Relativity, Derivation, Geometrical Representation, Experimental Verifications, Reality of Lorentz Contraction, Paradoxes, Visual Effects

### Other articles related to "length contraction, contraction, length":

Lorentz Ether Theory - Historical Development - Length Contraction
... an observer co-moving with the earth would not notice this contraction, because all other instruments contract at the same ratio ... In 1895 Lorentz proposed three possible explanation for this relative contraction The body contracts in the line of motion and preserves its dimension perpendicularly to it ... and intermolecular forces was used by Lorentz as a plausibility argument, the contraction hypothesis was soon considered as purely ad hoc ...
Minkowski Diagram - Length Contraction
... Relativistic length contraction means that the length of an object moving relative to an observer is decreased and finally also the space itself is contracted in this system ... together with the object, so that for him the object is at rest, it has the length OB at t'=0 ...
Trouton–Rankine Experiment - Description
... FitzGerald and Lorentz, independently of each other, proposed a length contraction of the experimental apparatus in the direction of motion (with respect to the Luminiferous aether) that would ... The first attempts to measure some consequences of this contraction in the lab frame (the inertial frame of reference of an observer co-moving with the experimental apparatus) were made in the ... at all), predicted that the Lorentz–FitzGerald contraction is not measurable in a co-moving frame, because these theories were based on the Lorentz transformation ...
Tests Of Special Relativity - Experiments Paving The Way To Relativity - Second-order Experiments
... and Lorentz (1892) that matter is contracted in the line of motion with respect to the aether (length contraction) ... That is, the older hypothesis of a contraction of electrostatic fields was extended to intermolecular forces ... However, since there was no theoretical reason for that, the contraction hypothesis was considered ad hoc ...
Length Contraction - Visual Effects
... Length contraction refers to measurements of position made at simultaneous times according to a coordinate system ... a photograph is taken from a distance, while length contraction can only directly be measured at the exact location of the object's endpoints ... Terrell published papers demonstrating that length contraction instead actually shows up as elongation or even a rotation in a photographic image ...

### Famous quotes containing the word length:

Your length in clay’s now competent,
A long war disturbed your mind;
John Webster (c. 1580–1638)