The equator is an imaginary line that divides the Earth into the Northern Hemisphere and Southern Hemisphere. Its length is about 24,901.5 miles (40,075 kilometers). The line crosses the continents of South America and Africa, as well as a number of islands, and runs through 14 countries, including Ecuador, Columbia, Brazil, Gabon, São Tomé and Príncipe, Congo, Zaire, Uganda, Kenya, Somalia, and Indonesia. The location of this imaginary line is indicated in many areas, making it possible to stand with a foot in each hemisphere. The geographical areas surrounding it are known as the equatorial regions, and they have a particular type of climate.
Latitude and Longitude
The location of any point on the Earth can be defined by its latitude and longitude, given in degrees (°). Lines of longitude all run from pole to pole, and they are all roughly the same length but are not parallel, as they converge towards the poles. Lines of latitude run at right angles to the longitude lines and are parallel, but they diminish in length towards the poles. The equator is at 0° latitude and is the longest such line, representing the circumference of the Earth. When a latitude for a location not on the equator is given, it is necessary to specify whether it is north or south of this line.
Day Length and Seasons
Due to the fact that the Earth wobbles slightly on its axis through the year, the higher latitudes experience summer and winter seasons, as well as variations in day length. At the equator, however, the effects of this wobbling are minimal. As a result, the region experiences 12 hours of daylight throughout the year and does not have clearly defined seasons, at least in terms of temperature.
The equatorial regions receive more heat from the Sun than any other area of the Earth’s surface, and heating of the atmosphere in these regions drives the world’s climate system. Warm air, which also contains a lot of moisture from the ocean, rises near the equator, flows outwards at high altitude, and descends again at mid latitudes, having lost most of its moisture. For this reason, the areas near the equator tend to be both warm and wet, while most of the world’s deserts lie within the mid latitudes.
Average daily maximum temperatures are typically about 80 to 90°F (27 - 32°C), but this is affected by altitude, with higher areas being cooler. Annual rainfall generally varies from about 98 inches (249 cm) to about 138 inches (350 cm). There is normally not a great deal of variation in temperature through the year, but rainfall often has a seasonal aspect, as it is affected by ocean currents and factors beyond the region. The rainy and dry seasons vary from place to place, with some areas experiencing high to very high rainfall all year round, and others having distinct relatively dry periods. The high temperatures and abundant moisture found in most equatorial areas have led to the growth of rainforests with a great diversity of plant and animal life.
The length of the equator has been measured very accurately by geographers and surveyors. According to a 2000 survey, to within 0.04 inches (1 mm) of accuracy, it is 131,479,775 feet 6.92 inches (40,075,035.535 m). Since the Earth bulges slightly around the middle, the equator is slightly longer than an imaginary circle drawn between the poles. If the heights of mountains are measured in terms of distance from the Earth’s center, instead of the more traditional height above sea level, the worlds’ highest mountain is not Everest, but Chimborazo in Ecuador, whose summit is further from the center of the Earth than that of any other mountain, due to its very low latitude.
Since the Earth is rotating, a person standing at the equator is traveling faster relative to a person at a high latitude. The speed of rotation at 0° latitude is 1,038 mph (1,670 kph), compared to 0 at the poles. For this reason, the equator is the ideal place to launch a spacecraft, as it is already traveling quite fast prior to launching and so requires less fuel.
The main factor in the formation of hurricanes is ocean temperature: where it is not high enough, they will not form. Although ocean temperatures at 0° latitude are high enough for hurricanes to form, these storms have not been observed to form anywhere within the range 5° north to 5° south. It is thought that this is because the Coriolis force — an influence due to the Earth’s rotation — is not strong enough here to cause the spinning motion required. Hurricanes also appear never to cross the equator, apparently because the Coriolis force always causes them to veer away to the north or south, depending on the hemisphere.