Who is credited with solving the issue of measuring longitude at sea in the 18th century?

The correct answer is John Harrison, who is renowned for his groundbreaking work in solving the problem of measuring longitude at sea during the 18th century. The challenge of determining a ship's longitude, which is the east-west position on the Earth, was critical for safe and accurate navigation.

Prior to Harrison's innovations, various methods to measure longitude, such as lunar distances or dead reckoning, were fraught with inaccuracies and could lead to disastrous results at sea. Harrison, a self-taught clockmaker, developed a series of marine chronometers, specifically H1, H2, H3, and ultimately H4, which were highly accurate timepieces capable of withstanding the conditions at sea. The H4, in particular, solved the problem as it enabled sailors to determine their precise longitude by comparing the time on the ship with the time at a known location, such as Greenwich Mean Time.

Harrison's dedication to producing a reliable marine chronometer, along with the innovative design and engineering solutions he implemented, directly contributed to safer navigation and the global expansion of maritime trade during that era. His success was so impactful that he was later recognized by the British government and was awarded a monetary prize for his contributions to maritime safety.