Earth is divided into halves called hemispheres for geographical and navigational purposes. The term ‘hemisphere’ means ‘half a sphere’ in Greek. These divisions assist in understanding global geography, climate patterns, and the distribution of land and water.
How Earth is Divided
Imaginary lines divide Earth into hemispheres. The two main lines are the Equator and the Prime Meridian. The Equator is a theoretical line at 0 degrees latitude, encircling Earth equidistant from the North and South Poles. This line spans approximately 40,075 kilometers (24,901 miles) in circumference, serving as the fundamental reference for north-south positioning.
The Prime Meridian is an imaginary line of longitude at 0 degrees, extending from the North to South Pole. It passes through Greenwich, England, also known as the Greenwich Meridian. The Prime Meridian and its anti-meridian (the 180th meridian) form a great circle, dividing Earth longitudinally. These two primary lines collectively form the basis for Earth’s four recognized hemispheres.
Northern and Southern Hemispheres
The Equator divides Earth into the Northern and Southern Hemispheres. The Northern Hemisphere is north of the Equator, and the Southern Hemisphere is south of it. The Northern Hemisphere contains a significantly larger landmass, accounting for approximately 67-68% of Earth’s land and home to about 87-90% of the global population. Major landmasses include all of North America, Europe, and Asia, along with roughly two-thirds of Africa and a small portion of South America. Seasons are distinct, with winter from December to March and summer from June to September, due to Earth’s axial tilt.
In contrast, the Southern Hemisphere is predominantly water, covering approximately 80.9% of its surface, and contains about 32.7% of Earth’s land. It supports a smaller portion of the world’s population, around 10-12%. Continents located entirely or mostly within it include Australia, Antarctica, most of South America, and about one-third of Africa. Seasons are opposite to the north; for example, summer spans from December to March. The greater oceanic influence results in generally milder climates compared to similar latitudes in the Northern Hemisphere. Continents like Africa, South America, and Asia have land in both the Northern and Southern Hemispheres.
Eastern and Western Hemispheres
The Prime Meridian (0 degrees longitude) and the 180th meridian divide Earth into the Eastern and Western Hemispheres. The Eastern Hemisphere lies east of the Prime Meridian and west of the 180th meridian. It includes most of Africa, Europe, Asia, and Australia, representing a larger landmass than the Western Hemisphere. Historically, it is sometimes referred to as the “Old World.”
Conversely, the Western Hemisphere is located west of the Prime Meridian and east of the 180th meridian. It primarily encompasses North and South America, often referred to as the “New World.”
Parts of Europe and Africa, such as Western Europe and West Africa, are also geographically located within the Western Hemisphere. The 180th meridian is closely associated with the International Date Line (IDL), which marks the transition between calendar days. The IDL is not a perfectly straight line; it zigzags to avoid splitting countries and island groups into different days. Africa, Europe, Antarctica, and Asia have land in both hemispheres, while Kiribati has territory in all four.