An equator is an imaginary line around the center of a planet or other celestial body. it is halfway between the north pole and the south pole, at 0 degrees latitude. An equator divides the planet into a northern hemisphere and a southern hemisphere. the earth is widest at its equator. the distance around the earth at the equator, its circumference, is 40,075 kilometers (24,901 miles). Earth’s diameter is also widest at the equator, creating a phenomenon called the equatorial bulge. The diameter of a circle is measured by a straight line that passes through the center of the circle and has its endpoints at the limit of that circle. scientists can calculate the diameter of latitudes, such as the equator and the arctic circle. The diameter of the earth at the equator is about 12,756 kilometers (7,926 miles). at the poles, the diameter is about 12,714 kilometers (7,900 miles). the equatorial bulge of the earth is about 43 kilometers (27 mi). The equatorial bulge means that people at sea level near the poles are closer to the center of the earth than people at sea level near the equator. equatorial bulge also affects the ocean: sea levels are slightly higher in equatorial regions than near the poles. the equatorial bulge is created by the earth’s rotation. As lines of latitude get larger, a point has to travel faster to complete one circle (revolution) in the same amount of time. The rate of rotation, or spin, at the Arctic Circle is slower than the rotation at the Tropic of Cancer, because the circumference of the Arctic Circle is much smaller and a point doesn’t have to travel as far to complete one revolution. the spin at the tropic of cancer is much slower than the spin at the equator. Near the poles, the earth’s rate of rotation, or spin, is close to zero. At the equator, the spin is about 1,670 kilometers per hour (1,038 miles per hour). Earth’s gravitational pull is slightly weaker at the equator due to its equatorial bulge. space launch sites. It takes a huge amount of energy to launch a satellite or other spacecraft out of the Earth’s atmosphere. it takes less energy (rocket fuel) to launch in lower gravity. less energy is also needed for launch when the spinning earth is already giving the satellite a boost of 1,670 kilometers per hour (1,038 miles per hour).
the united states launches most spacecraft from the kennedy space center in south florida, as close to the equator as possible in the continental united states. Other rocket launch facilities near the equator include North Shaba, Democratic Republic of the Congo, and Gan Island, Maldives. recently, mobile launch platforms, such as ocean odyssey, have successfully launched satellites into orbit from the equatorial pacific ocean. equatorial climates twice a year, during the spring and fall equinoxes, the sun passes directly over the equator. even during the rest of the year, equatorial regions often experience warm weather with little seasonal variation. As a result, many equatorial cultures recognize two seasons: wet and dry. the wet or rainy season usually lasts most of the year. the long, hot and rainy season creates tropical rainforests. Some of the largest rainforests in the world are found in the equatorial regions: the Amazon rainforest in South America, the Congo rainforest in central Africa, and the diverse rainforests of Southeast Asia that stretch from India to Vietnam. The humid climate means that the equatorial regions are not the hottest in the world, although they are among the closest to the sun. the water in the equatorial air cools it slightly. many cultures thrive in warm equatorial regions. The Fang of Gabon, for example, are successful farmers who take advantage of the warm temperature and long rainy season to grow maize, yams and bananas. The Fang also raise livestock that have adapted to the climate, such as goats and chickens. however, not all equatorial regions are hot and humid. Mount Kilimanjaro, Tanzania, is only 330 kilometers (205 miles) from the equator, but its elevation creates a cool, dry climate and even alpine glaciers. The Andes are another equatorial region that lacks the hot, humid climate often associated with the equator. The mountain range includes a nearly rainless desert (the Atacama) as well as some of the highest peaks on earth. here, too, cultures have thrived for thousands of years. The Aymara people of the Altiplano of Bolivia, Peru, and Chile are primarily an urban people who strongly identify with the innovative navigational successes of their ancestors. In the 20th century, the Aymara helped build railways across the high equatorial Andes. Many species of plants and animals thrive in equatorial climates. The ecosystems of the Amazon rainforest and the Congo, for example, are incredibly rich in biodiversity. A single hectare (2.47) of rainforest in Brazil can contain 750 species of trees and twice as many species of insects. Kenya’s equatorial savannah includes mammals such as lions, cheetahs, and elephants. The cold equatorial Andes are famous for their species of camelids: llamas, alpacas, vicuñas and guanacos.
