Spatial organization refers to the way areas are arranged on the Earth's surface. The equator is an imaginary line that divides the Earth into the northern and southern hemispheres. We viewed how major horizontal lines of latitude north and south of the Equator comprise the tropics. To the north is the Tropic of Cancer and to the south is the Tropic Capricorn. Kaitlin found their names very odd until I reminded her that navigators named them for celestial constellations. This area was referred to by many early navigators as the "horse latitudes." We then looked at vertical lines of longitude - specifically the Prime Meridian and the International Date Line. Lines of longitude divide Earth into the eastern and western hemispheres and also help to determine time zones.