Physics · Study 022
Compass Field
Hundreds of compass needles swing to follow the magnetic field between a north and a south pole. Move the red pole and watch the field redraw.
What you're looking at
Each needle sits at a fixed point and turns to match the direction of the field there. The field is the sum of two contributions, pushing away from the red north pole and pulling toward the dark south pole, each fading with the square of distance. Read together, the needles sketch the familiar arcs from pole to pole.
The idea behind it
Michael Faraday pictured magnetism this way, as lines of force filling space, long before there was mathematics for it. Scattering iron filings or setting out small compasses was how those lines were first made visible.
Try this
Move the pointer to carry the north pole. The south pole mirrors it on the other side.
