Scientific discovery changes the world! Discover the fascinating story behind one of the most important changes to nautical navigation in this nonfiction book for young readers. More than 300 years ago, explorers wandered the seas using unreliable maps. What they needed to know was the longitude of their locations, but for that they needed accurate time keeping. Unfortunately, no accurate source of time measurement at sea existed. In 1714 the British government decided to offer a reward to anyone who could solve the problem. Learned men and great thinkers alike tried unsuccessfully to work out a solution. They declared it unsolvable! Carpenter John Harrison was intrigued; he thought he might have a solution. He worked for years to design a clock that functioned accurately at sea, even though no one believed he could do it. Even after his timepiece was demonstrated effective at sea, he was still not acknowledged for his ingenious solution. It took many years and intervention by the king to grant Harrison the recognition and reward he deserved for solving the problem of how to accurately track longitude and for winning the British government prize. The book offers a detailed map of the world at that time and includes the advancements in the use of longitude since then.