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For an observer that moves very fast, not only the laws of simultaneity and geometry are invalid without Lorentz transformation, but also electromagnetic fields have to be transformed. In this applet an observer passes in *x*-direction an electric field oriented in *z*-direction. As a relativistic effect the observer can measure a magnetic field in *y*-direction.

This applet displays an event in two space time graphs, one for the motionless observer, the other for the moving observer. You can choose a velocity between zero and the speed of light. The angles of the coordinate axes changed by the Lorentz transformation are shown together with the projection of the event on the axes.

## Out of the *Wolfram Demonstrations Project*

Potentials and fields of oszillating charges are deformed when regarding relativistic velocities. In this Mathematica notebook the resulting changes in the electromagnetic energy density and Poynting vector are displayed.

Potentials and fields of oszillating charges are deformed when regarding relativistic velocities. In this Mathematica notebook the resulting changes in the electromagnetic energy density and Poynting vector are displayed.

*Note: Open the demonstrations with the free Mathematica CDF Player (Win,Mac,Linux) or Wolfram Mathematica (version 6 or higher).
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*The source code (*.nb file) is also available and can be opened with Wolfram Mathematica.*