We all know that lightning comes in zigzag bolts that strike from the sky. Except when it doesn’t, like, when it comes in a big circular glowing blue flash. Such is the weather phenomenon called ball lightning (which doesn't really streak indoors like the fanciful illustration here suggests). It’s rare and hard to predict, and because of that, researchers don’t know much about it. It can last for more than a second, which is long for lightning, but still … it’s hard to capture a second-long flash of light to study in the lab. Explanations have ranged from electrically charged meteorites to hallucinations induced by magnetism during storms. One theory is that when lightning strikes something it explodes in a cloud of highly energized nanoparticles, notes the Weather Channel, but for now that remains just speculation. If only we could ask Zeus.