Every time you look at a map or a globe, the Equator shows up as such a prominent feature that it’s almost hard to believe it’s imaginary. The Equator is only an imaginary line, and you could cross it back and forth without knowing you’ve passed it.
This may explain why sailors like to remind themselves that they’re “crossing the line” as they call it, by making quite a ceremony of it. The word equator comes from a Latin word meaning to equalize.
And this is what the Equator does. It divides the earth into the Northern and Southern Hemispheres. It is the imaginary line that encircles the earth midway between the North and South Poles.
Imaginary lines, encircling the earth parallel to the Equator are called “parallels.” The Equator is the zero line, and lines above and below it measure latitude for locating points on the earth’s surface.
The earth, as you know, is also divided on maps into regions. Starting at the top or north, we have the Arctic Region, the North Temperate Region, the Tropical Region, the South Temperate Region, and the Antarctic Region.
The Tropical Region, or the Equatorial Region, extends beyond the Equator to 23,5 degrees north latitude and to 23,5 degrees south latitude. Within this region, the rays of the sun come down vertically, and therefore it is always hot here.
Let’s see why this is so: The earth, as you know, has its axis tilted to its path around the sun. The Equator, therefore, is tilted to this path, too, and that tilt is exactly 23,5 degrees.
Because of this tilt, as the earth goes around the sun, the direct rays from it sometimes fall on the earth north of the Equator, sometimes directly on the Equator, and sometimes south of the Equator.
The sun, however, cannot be directly overhead more than 23,5 degrees from the Equator. This explains why the Equatorial Region is the only place on earth where the sun’s rays come down vertically. You can understand why, since this happens the year-round, it’s always pretty hot near the Equator!
Read: What Is a Rainbow?