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 at the mercy of starless nights and stormy weather. They followed the shoreline, navigating by recognizable landmarks and the stars, but often became lost or wrecked on the rocky coast. What they needed to know in order to navigate safely was the longitude of their location, but for that they needed accurate timekeeping. 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.