The Greenwich Meridian at 0 degrees longitude divides the Earth into Eastern and Western Hemispheres. Chosen in the 19th century, it set the standard for global time measurement and navigation ...
Lines of longitude run from the top of the Earth to the bottom ... The North Pole is 90°N and the South Pole is 90°S. Image caption, The globe above shows the Northern and Southern Hemispheres ...
"These gravity images are revolutionizing our ability to study the least understood continent on Earth—Antarctica." ...