Far-fetched stories about glowing spheres of light hovering above the ground during thunderstorms have appeared throughout the centuries: a young Czar Nicholas II claimed to see one during a church service in the 19th century, and 18th-century physicist Georg Richmann was believed to have even been killed by one. Until recently, stories were all we had of what's referred to as "ball lightning," which skeptics had attributed to everything from marsh gases to the blind spot of the human eye. But in 2012, completely by accident, Chinese scientists captured the phenomenon on camera. The researchers had set up special spectrum-analysis and high-speed video equipment to analyze regular lightning in northern China. One stormy evening, a bolt of lightning struck a kilometer away and sent a ball of glowing light into the air. The equipment recorded every moment as the ball lightning floated along the ground for just over 1.5 seconds, then vanished. Data from the researchers' video may back up a theory from 2000 that suggests ball lightning is caused by regular lightning vaporizing silicate compounds in the soil, which could glow thanks to interactions with the atmosphere.