Lines of longitude, also known as meridians, are imaginary lines that run from the North Pole to the South Pole and divide the Earth into the Eastern and Western Hemispheres. They measure the distance east or west of the Prime Meridian, which is an imaginary line that runs through the Royal Observatory in Greenwich, England and has a longitude of 0 degrees. Longitude is measured in degrees, minutes, and seconds, and lines of longitude are furthest from each other at the equator and converge at the poles. There are 360 degrees of longitude, with 180 degrees eastward and 180 degrees westward of the Prime Meridian. The International Date Line is located at 180 degrees longitude and is directly opposite the Prime Meridian. Longitude is used in conjunction with latitude to describe the exact location of any place on Earth.