John Harrison was an English carpenter and clockmaker born in 1693. He is best known for inventing the marine chronometer, a precise timekeeping device that allowed sailors to determine their longitude at sea. His work significantly improved navigation and contributed to safer sea travel. Harrison's most famous chronometer, known as H4, was completed in 1759. It successfully demonstrated the ability to keep accurate time over long voyages, earning him recognition and a reward from the British government. His innovations laid the groundwork for modern timekeeping and navigation, influencing maritime exploration.