There are four hemispheres on Earth: the Northern Hemisphere, Southern Hemisphere, Eastern Hemisphere, and Western Hemisphere. The Northern and Southern Hemispheres are divided by the equator, with the Northern Hemisphere encompassing much of North America, Europe, and Asia, while the Southern Hemisphere includes parts of South America, Africa, Australia, and Antarctica. The Eastern and Western Hemispheres are divided by the Prime Meridian and the International Date Line. This division helps in geographical orientation, climate studies, and time zone definitions, affecting global navigation and travel.