An electric field playground
Move the charge. Watch the field catch up.
Hold or drag one finger or the left mouse button to accelerate toward the pointer. Farther from the charge means a stronger boost, measured as a fraction of the screen so it feels the same at any zoom. Pointer boosts ease in, turn and fade out smoothly. Release to coast. W A S D and the on-screen keys also work. Boost strength adjusts both controls. Speed stays below 0.92c.
Every line connects the charge to its older field. Changes spread at c, leaving outward-travelling bends. Amber emphasizes the acceleration contribution; color is not a calibrated field-strength or energy scale.
Contraction on: numerical field lines of the relativistic point-charge electric field, shown in the plane of motion. For steady motion, the lines remain radial but crowd sideways.
Contraction off: an illustrative comparison with evenly spaced radial lines during steady motion. It keeps the same trajectory and light-speed propagation; it is not the full relativistic Maxwell field.
The letters TEST PARTICLES are made of positive test particles attached to fixed anchors by damped springs. The local, delayed electric field displaces them; passing radiation makes the letters wobble. They turn from purple to red as their distance from their anchors increases. Their response is scaled for visibility. They do not alter the source or field. Use Test particles to hide or show them.
Right-drag or move two fingers together to pan. Pinch two fingers or scroll to zoom. After a two-finger gesture, lift both fingers before boosting again. Recenter restores automatic following. Pause to compare the modes at the same instant; zoom, panning and settings remain adjustable while paused.
Physics background: Feynman: fields of a moving charge · Electromagnetic radiation.All simulation code is included in this file. No connection is needed.