Longitude is an essential concept in geography, referring to the angular distance of any point on Earth's surface from the prime meridian, which passes through Greenwich, England. This measurement is critical for navigation and mapping purposes, as it allows us to pinpoint locations on a global scale with precision.

Historically, determining longitude at sea was a significant challenge for explorers and navigators. The inability to accurately calculate longitude led to numerous maritime disasters until John Harrison invented the marine chronometer in the 18th century. This invention allowed sailors to carry a precise timekeeping device that could be used to determine their longitudinal position by comparing local solar time with the time at a fixed reference point.

Today, modern technology such as GPS (Global Positioning System) has made the determination of longitude even more accurate and accessible. By using signals from multiple satellites, GPS receivers can calculate the exact longitude and latitude of any location on Earth within a few meters, revolutionizing navigation, surveying, and many other fields.

Understanding longitude is crucial not only for practical applications but also for scientific research, particularly in areas like climate studies and oceanography, where longitudinal data helps track changes over vast distances.