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Lightning is one of the most enigmatic natural phenomena, and scientists still don’t entirely understand it. But that’s not stopping them from putting it to use. If scientists knew in 1752 what they know now, Benjamin Franklin may never have ventured out into the storm, much less flown a kite in it. Franklin wanted to prove the electrical nature of lightning, and fortunately—unlike at least one other attempting similar experiments at the time— he lived to tell the tale. Since Franklin’s famous exploit, a lot of what goes on with lightning has been delineated. As a thundercloud forms, large particles inside it, like granular snow pellets, sink to the lower part while smaller particles, like ice crystals, rise to the top. As the tempest grows, collisions between rising and falling particles result in the transfer of electrons to the larger particles, so the lower part of the cloud becomes negatively charged, while the top becomes positively charged. This separation of charge creates an electric field both within the cloud and between the cloud and the ground, which is partially relieved by the occasional momentary flow of electrons from one layer to another. This is lightning. 1663  March 2018 23