Encyclopedic Entry

Representations of the Eastern Hemisphere are dominated by Africa, Asia, and the Indian Ocean.

Map by National Geographic

Internal Hemisphere
The word "hemisphere" is usually used to refer to halves of the Earth, but it is also used to identify the halves of the brain. The brain is divided down the middle into the right and left hemispheres. Each brain hemisphere is considered to be specialized for certain behaviors. For example, the right hemisphere of the brain controls muscles on the left side of the body, and the left hemisphere of the brain controls muscles on the right side of the body. The left side of the brain is also dominant for language skills, mathematical calculations, and logic. The right side of the brain is dominant for visual imagery, music, and face recognition.

Any circle drawn around the Earth divides it into two equal halves called hemispheres. There are generally considered to be four hemispheres: Northern, Southern, Eastern, and Western.

The Equator, or line of 0 degrees latitude, divides the Earth into the Northern and Southern hemispheres. The Northern Hemisphere contains North America, the northern part of South America, Europe, the northern two-thirds of Africa, and most of Asia. The Southern Hemisphere contains most of South America, one-third of Africa, Australia, Antarctica, and some Asian islands.

There are differences in the climates of the Northern and Southern hemispheres because of the Earth's seasonal tilt toward and away from the sun. In the Northern Hemisphere, the warmer summer months are from June through September. In the Southern Hemisphere, summer begins in December and ends in March.

The Earth can also be divided into hemispheres along meridians, or lines of longitude. The prime meridian, or 0 degrees longitude, and the International Date Line, 180 degrees longitude, divide the Earth into Eastern and Western hemispheres. Many geographers consider the 20 degree west line of longitude and the 160 degree east line of longitude as the Eastern and Western hemispheres. This calculation is made so that Africa and Europe are not split.

The idea of Eastern and Western hemispheres has become politically and historically significant since European nations began colonizing North America and South America. In this context, the Eastern Hemisphere is sometimes called the "Old World," and the Western Hemisphere is called the "New World." However, the Western Hemisphere is a purely geographic term and should not be confused with other mentions of the "western" world, which is often used to describe parts of Europe, North America and other world regions that share some economic, social, and cultural values.


Term Part of Speech Definition Encyclopedic Entry



all weather conditions for a given location over a period of time.

Encyclopedic Entry: climate



to establish control of a foreign land and culture.



set of facts having to do with a specific event or situation.



main or most important.



our planet, the third from the Sun. The Earth is the only place in the known universe that supports life.

Encyclopedic Entry: Earth

Eastern Hemisphere


area of the Earth east of the prime meridian and west of the International Date Line.



imaginary line around the Earth, another planet, or star running east-west, 0 degrees latitude.

Encyclopedic Entry: equator



half of a sphere, or ball-shaped object.

Encyclopedic Entry: hemisphere

International Date Line


line of longitude at roughly 180 degrees. East of this line is one day earlier than west.



distance north or south of the Equator, measured in degrees.

Encyclopedic Entry: latitude

left hemisphere


half of the brain that dominates language skills, mathmatical calculations, and logic.



system of scientific or researched reason.



distance east or west of the prime meridian, measured in degrees.

Encyclopedic Entry: longitude



line of longitude, dividing the Earth by north-south.



tissue found in animals that expands and contracts, allowing movement.



political unit made of people who share a common territory.

Encyclopedic Entry: nation

New World


the Western Hemisphere, made up of the Americas and their islands.

Northern Hemisphere


half of the Earth between the North Pole and the Equator.

Old World


the Eastern Hemisphere, especially Europe, Asia, and Africa.

prime meridian


imaginary line around the Earth running north-south, 0 degrees longitude.

Encyclopedic Entry: prime meridian

right hemisphere


half of the brain that dominates visual imagery, music, and face recognition.



important or impressive.

Southern Hemisphere


half of the Earth between the South Pole and the Equator.



time of year when part of the Earth receives the most daylight: The months of June, July, and August in the Northern Hemisphere and the months of December, January, and February in the Southern Hemisphere.

Western Hemisphere


area of the Earth west of the prime meridian and east of the International Date Line.


Media Credits

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Kim Rutledge
Melissa McDaniel
Diane Boudreau
Tara Ramroop
Santani Teng
Erin Sprout
Hilary Costa
Hilary Hall
Jeff Hunt


Tim Gunther
Mary Crooks, National Geographic Society


Kara West
Jeannie Evers

Educator Reviewer

Nancy Wynne


Caryl-Sue, National Geographic Society


Dunn, Margery G. (Editor). (1989, 1993). "Exploring Your World: The Adventure of Geography." Washington, D.C.: National Geographic Society.

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