Why does lightning follow a zigzag path?

Lightning does not move like a straight wire because the atmosphere resists electrical flow until the electric field becomes strong enough to ionize the air. A stepped leader descends in short jumps, seeking a path of least resistance through turbulent air with changing humidity and charge distribution. When it nears the ground, upward streamers can connect, and the return stroke produces the bright flash we see. The zigzag shape is a visible record of the irregular route the discharge took through the atmosphere. Lightning has been studied in detail since the 18th century, especially after Benjamin Franklin’s experiments.