Ancient sailors used lodestone, a rock naturally magnetized by lightning, to create the world's first portable compasses.

Lodestone is composed of magnetite, a ferrimagnetic mineral with the chemical formula Fe3O4. While all magnetite has some magnetic properties, only a small fraction of it qualifies as lodestone. Research led by Peter Wasilewski at NASA's Goddard Space Flight Center suggests that lodestone is created when magnetite is hit by a lightning strike. The massive electrical discharge, which can reach 30,000 amperes, generates a magnetic field strong enough to permanently reorient the mineral's crystalline structure.The first recorded mentions of lodestone's magnetic properties date back to the 6th century BCE in Greek texts by Thales of Miletus. By the 12th century, during the Song Dynasty in China, the first maritime compasses were developed using these stones. European sailors followed suit around 1187, as documented by the English monk Alexander Neckam. These early navigators would rub an iron needle against the lodestone to transfer the magnetic charge, a process known as magnetic induction.This technology was the cornerstone of the Age of Discovery in the 15th and 16th centuries. Without the ability to find magnetic north, explorers like Christopher Columbus and Vasco da Gama could not have navigated the open seas far from the sight of land. Modern geological studies confirm that lodestones are typically found near the Earth's surface where lightning is most likely to strike. This explains why magnetized magnetite is rarely found deep underground, reinforcing the theory of its atmospheric origin.