KentuckyFC writes "Transcranial magnetic stimulation involves placing a human in a rapidly changing magnetic field powerful enough to induce eddy currents in the brain. Focus the field in the visual cortex, for example, and the induced eddys cause the subject to 'see' lights that appear as discs and lines. Move the field within the cortex and the subject sees the lights move too. Physicists have calculated that the fields associated with certain kinds of multiple lightning strikes are powerful enough to induce the same kind of visual hallucinations in anybody unlucky enough to be within 200 meters or so. These fields ought to induce hallucinations that would take the form of luminous lines and balls that float in front of the subject's eyes, an effect that would explain observations otherwise classed as ball lightning, say the scientists."