However, recent developments have shed some light on the subject. Contrary to ordinary lightning (which is explained using slow electrons), dark lightning is caused by high energy electrons colliding with surrounding air molecules, releasing gamma rays in the process. And, believe it or not,these bursts have an interesting effect on humans. Most commonly, humans are “hit” by dark lightning when flying through thunderstorms. At 12,000 meters, the radiation dose if hit by one of these bursts is around the same as 10 chest X-rays. However, at 4,900 meters (the middle of storms), the dose is 10x stronger and equivalent to a full-body CT scan. In general, an encounter with one of these bursts will provide enough radiation deemed “safe” for human tolerance for one year. But don't worry: a chance of getting “hit” by dark lightning is very small, since pilots avoid storms and dark lightning is relatively rare.