According to Einstein's theory of special relativity, the observed length of objects is dependent upon the speed of that object. For objects moving at relativistic speeds, there is an observable contraction in the length relative to an observer in a stationary reference frame. For instance, if a spaceship traveled past Earth at relativistic speeds, an observer on Earth would observe the length of the ship to be less than it would be observed when at rest. The following animation allows you to investigate this phenomenon.


  1. Use the user input box to modify the speed of the spaceship; use values between 0 and 99.999% the speed of light.
  2. Click on the Runbutton to observe the animation.
  3. Observe the values of spaceship speed and relativistic length (L) for a 202-m length spaceship (Lo).
  4. Repeat for several values of spaceship speed. Use the Reset button if you encounter any problems.

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