Any circle drawn around 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 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 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.

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 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.

Internal Hemisphere

The word “hemisphere” is usually used to refer to halves of 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.

climate
noun

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

to establish control of a foreign land and culture.
context
noun

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

main or most important.
Earth
noun

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

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

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

half of a sphere, or ball-shaped object.
International Date Line
noun

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

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

left hemisphere

noun

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

system of scientific or researched reason.
longitude
noun

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

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

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

political unit made of people who share a common territory.
New World
noun

the Western Hemisphere Made up of the Americas and their islands.
Northern Hemisphere
noun

half of the Earth between the North Pole and the Equator.
Old World
noun

the Eastern Hemisphere, especially Europe, Asia, and Africa.
prime meridian
noun

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

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

important or impressive.
Southern Hemisphere
noun

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

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
noun

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