Ekvaattorin

Ekvaattorin, Finnish for the equator, is the imaginary great circle around the Earth that lies equidistant from the geographic North and South Poles. It corresponds to 0 degrees latitude and serves as a fundamental reference line in geography and cartography. The equator divides the Earth into the Northern and Southern Hemispheres and is approximately 40,075 kilometers long along the surface. Because the Earth is an oblate spheroid, the equator is longer than any circle of latitude, while the meridional circumference is about 40,008 kilometers, roughly 67 kilometers shorter.

The equator passes through oceans and several land areas in multiple regions, including parts of South America, Africa, and Asia, as well as numerous islands in the Pacific and Indian Oceans. It is a key reference for solar exposure and climate, with regions near the equator typically exhibiting tropical climates, high rainfall, and relatively small seasonal temperature variation. The Intertropical Convergence Zone and other atmospheric patterns strongly influence rainfall along the line.

In astronomy, the Earth’s equator projects onto the celestial sphere as the celestial equator, which forms the basis for the celestial coordinate system used to specify right ascension and declination. Geodetically, the equator is tied to the Earth’s rotation and serves as a reference plane for mapping, satellite orbits, and global navigation.