The equator is an imaginary line that divides the earth into two equal parts called the Northern Hemisphere and the Southern Hemisphere.Equator, in geography, an imaginary line circling the earth midway between the North and South poles. This great circle, 24,902 miles (40,076 km) in circumference and 7,927 miles (12,757 km) in diameter, divides the earth into the Northern and Southern hemispheres. It lies 6,215 miles (10,002 km), or 90° of latitude, from each pole. Beginning at the Equator, north and south distances are measured in degrees of latitude. Degrees of longitude are about 69 miles (111 km) long at the Equator.
The rays of the sun strike vertically on the Equator twice each year—usually March 21 and September 23. These dates are the equinoxes. During the rest of the year the sun's rays strike vertically in either the Northern Hemisphere or the Southern Hemisphere.
Equatorial climates are often assumed to be the hottest in the world, but this is incorrect. The hottest climates are found in the interior of the large land masses to the north, in such lands as the Sahara desert, Saudi Arabia, Iran, and India. Most of the area near the Equator is water and does not heat quickly. Some of the land on the Equator is at a high elevation, which also moderates the climate.
The celestial equator is an imaginary line that circles the celestial sphere, or visible universe, in the same way as the geographic, or terrestrial, equator circles the earth. The celestial equator divides the sky equally into northern and southern hemispheres. It is used to locate heavenly bodies.
