Length Contraction Visualization: Pole and Barn

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The pole and barn experiment is the standard textbook example of length contraction in special relativity. Use the buttons to switch between the frames of reference of the pole and barn. Adjust the sliders to change the speed and time for the experiment.


Length contraction is a fundamental aspect of the theory of special relativity. When there is a relative velocity between two inertial frames of reference, there will be an apparent change in length of the objects in one frame as viewed from the other frame. This effect is only apparent at velocities close to the speed of light, making it hard to get an intuitive feel for how objects appear in the theory. The standard example is the pole and barn thought experiment of Taylor and Wheeler. The paradox is that one person sitting in the barn will see the pole fit entirely inside the barn while a person running along with the pole will see a shortened barn into which his pole cannot fit. The explanation of this apparent logical contradiction includes the relativity of simultaneity, which can be observed in this Demonstration by examining the order of events in one frame compared to the other.


Contributed by: Grant A. Riley (March 2011)
Advice and Assistance by: Kenneth E. Caviness
Open content licensed under CC BY-NC-SA



E. F. Taylor and J. A. Wheeler, Spacetime Physics, New York: W. H. Freeman and Company, 1992.

P. A. Tipler and R. A. Llewellyn, Modern Physics, New York: W. H. Freeman and Company, 1999.

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