The equator is a clear and accurate line around Earth that makes measuring latitude a precise science, but when it came to figuring out how to do that with longitude, British sailors were at a loss. Until they devised a competition. Longitude is the angular distance of one’s position east or west of Greenwich, England. It’s what lets us know exactly where we are on Earth by knowing which hemisphere we’re in, without needing to figure out which country, state, city, or town we’re in. For example, if you were in London and talked to someone in Los Angeles, they would be seven hours ahead of you.
In 1592 Queen Elizabeth I put together an international committee that offered a £20 gold prize for the person who could come up with an accurate way of measuring longitude at sea. The challenge was tough because there are no obvious landmarks below the surface of the water to compare our location with.
The winner was John Harrison who created a watch that could keep accurate time as it traveled long distances on land and aboard ship–and he got paid £4200 for his trouble!