In 1900, Greek divers pulled up what looked like a lump of corroded junk from a shipwreck and accidentally rewrote the history of technology. Hidden inside was the Antikythera mechanism, a 2,000-year-old device packed with precision gears that could predict eclipses, track the Sun, Moon, and planets, and even mark ancient festivals. In other words: humanity’s first computer.

This video from TED Ed breaks down how it worked and why it still blows minds today. Check it out!