The line that divides the Earth into the Eastern and Western Hemispheres is called the Prime Meridian. Located at 0 degrees longitude, the Prime Meridian runs from the North Pole to the South Pole and passes through Greenwich, London, England. It is a fundamental reference point for global navigation and cartography, along with the International Date Line, which is located at 180 degrees longitude, providing a logical division of the globe. The Prime Meridian is essential in establishing global time zones and helps geographers define and navigate coordinates on maps.