Dividing Earth Into Hemispheres

The Earth is, almost, but not quite, a sphere that rotates around its axis. Scientists call this shape a spheroid or ellipsoid. If we draw a line passing through the center of the Earth along its rotational axis, the line would pass through the North and the South Pole.

The Equator is an imaginary line perpendicular to this axis. It is equidistant from the North and South Poles, and divides the globe into 2 equal halves called the Northern Hemisphere and the Southern Hemisphere.

Most locations near the Equator experience consistently high temperatures throughout the year. They also experience at least 12 hours of daylight every day during the year. On the Equinoxes – September and March – the sun is directly overhead the Equator, resulting in almost exactly 12 hour days and 12 hour nights.

The Equator passes through 14 countries, including Uganda, Kenya, Somalia, Indonesia, Ecuador, Colombia, and Brazil.

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LATITUDE - Imaginary Circles

Often called parallels or circles of latitude, latitudes are imaginary circles parallel to the Equator. They are named after the angle created by a line connecting the latitude and the center of the Earth, and the line connecting the Equator and the center of the Earth.

Latitudes specify the north-south position of a location on the globe. Locations in the Northern Hemisphere are identified by northern latitudes and are assigned a suffix of N for north. Southern Hemisphere locations, on the other hand, are on southern latitudes and are assigned a suffix of S for south.

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Notable Latitudes

The Equator represents 0° latitude, while the North and South Poles represent 90° North and 90° South latitudes. In addition to the Equator, there are four other major latitudes that are usually found on maps and globes. The positions of these latitudes are determined by the Earth's axial tilt.

• The Arctic Circle is the latitude 66° 34′ North. All locations falling North of this latitude are said to be in the Arctic Circle.
• The Antarctic Circle on the other hand, is the latitude 66° 34′ south. Any locations falling south of this latitude are said to be in the Antarctic Circle.
  • Places in both the Arctic and Antarctic circles experience extreme weather, and experience the Midnight Sun.
• The latitude 23° 26′ North is also known as the Tropic of Cancer. It marks the northern-most position on the Earth, where the Sun is directly overhead at least once a year. This happens during the June Solstice, when the Earth’s Northern Hemisphere is tilted towards the Sun.
• The Tropic of Capricorn is the latitude that lies at 23° 26′ South of the Equator. It is the southern-most position on the globe, where the sun is directly overhead during the December Solstice.

Sometimes, latitudes north of the Equator are denoted by a positive sign. Latitudes south of the Equator are given negative values. This eliminates the need to add whether the specified latitude is north or south of the Equator.

East-West Locations

Longitudes are geographical positioning markers that run from the geographical North Pole to the geographical South Pole, intersecting the Equator. They meet at both Poles, and specify the east-west position of a location.

Longitudes are therefore imaginary circles that intersect the North and South Poles, and the Equator. Half of a longitudinal circle is known as a Meridian. Meridians are perpendicular to every latitude.

Unlike, latitudes, there is no obvious central longitude. However, in order to measure the position of a location based on the longitude, cartographers and geographers over the course of history have designated different locations as the main longitudinal reference point. Today, the meridian line through Greenwich, England is considered as the reference point for longitudes. This line is also known as the Prime Meridian.

The Prime Meridian is set as 0° longitude and it divides the Earth into the Eastern and the Western Hemisphere. All the other longitudes are measured, and named after the angle they make with respect to the center of the Earth from the intersection of the Meridian and the Equator.

Since a sphere has 360 degrees, the Earth is divided into 360 longitudes. The meridian opposite the Prime Meridian (on the other side of the Earth) is the 180° longitude and is known as the anti meridian.

Modern timekeeping systems use longitudes as references to keep time. Time zones are defined by the Prime Meridian and the longitudes.