To help us navigate around the Earth, we draw imaginary lines around it. First, we divide it into two parts. Through the middle, splitting the globe into two hemispheres, is the Equator. The half above the Equator is known as the Northern Hemisphere, and the lower half is known as the Southern Hemisphere.
Then, we draw lines parallel to the Equator. These, we call latitudes. The latitude of a place basically tells us how far a place is from the Equator. We express it as degrees north or degrees south. The equator, therefore, has zero latitude (0º). The North Pole is at 90ºN, and the South is at 90ºS.
We now draw lines from the North Pole to the South Pole. These lines are not parallel; instead, they meet at the two poles. We call these lines longitudes. As with latitudes, we need to express them in relative to something else, so a line passing to the Royal Observatory, Greenwich (near London) was chosen as the zero-longitude reference line.
Places to the east of this line are in the eastern hemisphere, and places to the west are in the western hemisphere. The maximum longitude is 180ºE or 180ºW. This is actually the same line.
Using the latitude and longitude (we call them coordinates), we can locate any point on earth. Two of the most extreme points on earth are Attu Island, in Alaska, at 52ºN 172ºE, and Caroline Island, in the Pacific Ocean, at 9ºS 150ºW.
Now, using the map below (or use an atlas), try the quiz. Click on the map for a larger image.