Length contraction
A moving object's length is measured shorter than its proper length.
Length contraction is the phenomenon that a moving object's length is measured to be shorter than its proper length, which is the length as measured in the object's own rest frame. It is also known as Lorentz contraction or Lorentz–FitzGerald contraction and is usually only noticeable at a substantial fraction of the speed of light. Length contraction is only measured in the direction in which the body is travelling.
- known_for
- Postulating length contraction (Lorentz–FitzGerald contraction) to explain the Michelson–Morley experiment
- field
- Physics
- key_figures
- George FitzGerald, Hendrik Antoon Lorentz, Joseph Larmor, Henri Poincaré, Albert Einstein, Hermann Minkowski, James Terrell, Roger Penrose
Lore & Background
Although both FitzGerald and Lorentz alluded to the fact that electrostatic fields in motion were deformed, it was considered an ad hoc hypothesis, because at this time there was no sufficient reason to assume that intermolecular forces behave the same way as electromagnetic ones. Yet it was shown by Henri Poincaré (1905) that electromagnetic forces alone cannot explain the electron's stability, so he had to introduce another ad hoc hypothesis: non-electric binding forces that ensure the electron's stability, give a dynamical explanation for length contraction, and thus hide the motion of the stationary aether.
Reader's Guide
Albert Einstein removed the ad hoc character from the contraction hypothesis, declared the aether to be 'superfluous' along with the concept of any absolutely stationary space and discussed length contraction effects in his 1905 paper on his theory of special relativity. Einstein proposed that Lorentz's transformation apply to both electromagnetism and mechanics. Hermann Minkowski gave the geometrical interpretation of all relativistic effects by introducing his concept of four-dimensional spacetime. The numerous and confusing visual effects of combination of length contraction and the finite speed of light were poorly understood at first. Terrell's paper named 'Invisibility of the Lorentz Contraction' said a meter stick would appear to be rotated and the contraction itself could measure from photographs without corrections for the finite velocity of light.
Did You Know?
- Lorentz believed length contraction represented a physical contraction of the atoms making up an object.
- Albert Einstein removed the ad hoc character from the contraction hypothesis in his 1905 paper on special relativity.
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