Ekvaattori

Ekvaattori, which in Finnish refers to the equator, is the imaginary circle around the middle of the Earth at 0 degrees latitude. It is defined as the set of points on the Earth's surface that are equally distant from the North and South Poles, effectively dividing the planet into Northern and Southern Hemispheres. The equator is the longest line of latitude and marks the approximate midpoint of the planet’s circumference.

The Earth’s equatorial circumference is about 40,075 kilometers (24,901 miles). The equatorial radius is roughly 6,378 kilometers (3,963 miles), reflecting the Earth’s oblate shape. Because of this shape, the equator is about 21 kilometers larger in radius than the polar radius.

For astronomy and climate, the equator has notable features. The Sun is directly overhead at the equator twice a year, on the days of the vernal and autumnal equinox. The subsolar point—the location where the Sun is at zenith—migrates between the Tropic of Cancer and the Tropic of Capricorn over the year, but at the equator the Sun is near the zenith at solar noon during the equinoxes. The region around the equator experiences a tropical climate with high rainfall and dense biodiversity, influenced by the Intertropical Convergence Zone.

In geography, the equator serves as a reference line for latitude and is used to describe hemispheric location and climate zones. It passes over both oceans and a number of countries in South America, Africa, and Asia-Pacific, as well as several Pacific islands.