Magnetic probes around a bar magnet. These are Magnaprobes, and eight have been placed around the central bar magnet (red). Each Magnaprobe consists of a small bar magnet suspended in a gimbal mounting. The mounting allows the magnet to swivel and align with the direction of another magnetic field, in this case the one produced by the central bar magnet. This shows the direction of the magnetic field lines, running parallel to the magnet on either side, and spraying outwards or inwards at either end.