Equator

The equator is an imaginary line that circles the middle of the Earth. It splits our planet into two halves, called the Northern and Southern Hemispheres. This line is located at 0 degrees latitude.

On and near the equator, the sunlight is very strong around noon all year. The sun appears almost straight up in the sky, which helps keep temperatures steady. During special days called equinoxes, the sun shines directly over the equator, giving everywhere on Earth almost exactly 12 hours of day and 12 hours of night.

The equator is not just for Earth. Any round object that spins, like a planet, has an equator too. It is the line that is exactly halfway between the north and south poles and runs perpendicular to the object's spinning axis.

Etymology

The word "equator" comes from an old Latin phrase. This phrase means "circle equalizing day and night." People used this word to describe the line where day and night are about the same length.

Overview

The equator is an imaginary line around the middle of Earth. It splits Earth into two halves: the Northern and Southern Hemispheres. It is located at 0° latitude. The equator is a special kind of line called a great circle, which goes through the center of our planet.

When the Sun is directly above the equator, it is called an equinox. This happens twice a year in March and September. Places on the equator see the Sun rise and set very quickly. Days and nights are almost the same length all year. Earth also bulges a little at the equator, making it wider here than at the poles.

Geodesy

Further information: Earth ellipsoid and Reference ellipsoid

Precise location

The exact spot of the equator moves a little because Earth's spinning axis shifts each year. Long ago, the equator was in very different places. Ocean currents left clues in rocks showing these changes. Volcanoes also give hints about how Earth's axis moves.

Exact length

Main article: Earth's circumference

Scientists have measured the distance around Earth at the equator very carefully. Using special tools, they found it to be about 40,075 kilometres or 24,902 miles long. Earth isn't a perfect ball; it's slightly squashed, which makes the equator a bit longer than paths going over the poles.

Equatorial countries and territories

The equator passes over both land and sea in many places around the world. It crosses through eleven countries, starting from the Prime Meridian and moving east. Indonesia has the longest stretch of the equator running through it.

The equator also touches the waters near three other countries: Maldives, Kiribati, and the United States. Even though it’s in the name, Equatorial Guinea does not actually touch the equator, though its island of Annobón is close to it.

Equatorial seasons and climate

Main articles: Season and Effect of Sun angle on climate

Further information: Tropics

The equator changes how seasons and climate work on Earth. Because Earth tilts, the Northern and Southern Hemispheres take turns facing more toward or away from the Sun. The side facing the Sun gets more sunlight and has summer. The other side gets less sunlight and has winter.

Near the equator, the amount of sunlight changes differently than in places farther north or south. The equator gets the most direct sunlight during the equinoxes, when day and night are about the same length everywhere on Earth. Even during the solstices, when one pole faces the Sun more directly, temperatures near the equator stay warm. The tilt of Earth isn’t enough to greatly reduce the Sun’s strength there. This means places near the equator don’t have big temperature changes like other parts of the world. Instead, they usually stay warm all year.

Line-crossing ceremonies

Main article: Line-crossing ceremony

Many sailors and passengers have fun when they cross the equator for the first time. These celebrations are exciting and often include games and playful traditions. On some ships, people might dress up as a famous sea character to make the event special and memorable for everyone.