You’ve no doubt heard of ball lightning – perhaps even experienced it firsthand. But although the phenomenon has been known for millennia, it happens infrequently enough that there have always been doubts about its validity. Physicists at the University of Innsbruck in Austria think that ball lightning might just be a trick on the brain, having nothing to do with sight. The mind can see many things without the need of photons zipping through the eyeball first. Just ask a colleague to whack you hard in the back of the head with his iPad, and you’ll surely experience the sight of bright flashes – and maybe some cartoon stars or birdies, too. These phenomena are called phosphenes. Aside from violent strikes to the noggin, however, more gentle natural processes also may affect the mind’s eye, including strong magnetism. Plasma physicists Alexander Kendl and Josef Peer use artificial lightning and luminous fireballs to study the effects of strong electromagnetism on vision. Courtesy of the University of Innsbruck. In Innsbruck, Alexander Kendl and doctoral student Josef Peer study the electromagnetic fields of lightning strokes, varying their strength and duration. They report in the June 28, 2010, issue of Physics Letters A that sufficiently strong magnetic fields induced by close-by lightning strikes can induce electrical fields in the brain, especially near the visual cortex. If there are several strong bolts in succession near an observer, the induced electrical field might produce phosphenes that register as rounded electrical effects, or ball lightning. The results are inconclusive thus far, but they may go a long way toward explaining a quite rare experience. The research also may provide insight into the unintended consequences of placing the human brain too close to powerful magnetic forces – who knows what someone will think they see next?