The Equator is an imaginary line that runs around the middle of the Earth at 0° latitude, exactly halfway between the North Pole and the South Pole. It is about 40,075 km (24,901 miles) long and splits the planet into the Northern Hemisphere and the Southern Hemisphere. It crosses the land of 11 countries and the sea belonging to 2 more, which is why most lists say 13: São Tomé and Príncipe, Gabon, the Republic of the Congo, the Democratic Republic of the Congo, Uganda, Kenya, Somalia, the Maldives, Indonesia, Kiribati, Ecuador, Colombia and Brazil. Places on the Equator stay hot all year, and their days and nights are each about 12 hours long in every month.
Zero Degrees: How the Equator Wraps Around the Earth
Imagine the Earth as a big ball spinning in space. The Equator is the belt around its fattest middle.
Every other line of latitude is measured from the Equator. If you walk north, the numbers go up until you reach 90° North at the North Pole. If you walk south, they go up to 90° South at the South Pole. The Equator is the starting point, so it is 0°.
The name comes from Latin. Scholars in the Middle Ages called it aequator, from a phrase meaning the circle that makes day and night equal.
The Equator is also special in shape. It is the only line of latitude that is a great circle, cutting the Earth into two equal halves.
Here is a surprise: the Earth is not a perfect ball. It bulges a little at the middle, because it spins. Across the Equator, the Earth is about 43 km wider than it is from pole to pole. So the Equator is a tiny bit longer than a circle drawn through both poles.
Most of the Equator runs across water. About 31,361 km of it crosses oceans and seas, and only about 8,714 km crosses land.
The 13 Countries on the Line, From São Tomé to Brazil
Start where the Equator meets the Prime Meridian, off West Africa, and travel east.
- São Tomé and Príncipe. Our first stop is a tiny islet called Ilhéu das Rolas, just south of São Tomé Island. Only 76 people lived there in the 2012 census. A Portuguese navy officer, Gago Coutinho, proved the Equator crosses it during a survey between 1915 and 1918.
- Gabon. We reach the African mainland on the Atlantic coast. Gabon is a land of thick rainforest.
- Republic of the Congo. The line keeps going through more forest.
- Democratic Republic of the Congo. This is a huge country, and the Equator crosses the wide Congo rainforest here.
- Uganda. The town of Kayabwe, on the road from Kampala to Masaka, sits right on the line. The Equator also crosses the northern part of Lake Victoria, the biggest lake in Africa.
- Kenya. The town of Nanyuki has an Equator sign beside the main road, and the peaks of Mount Kenya rise just 16.5 km south of the line.
- Somalia. The line leaves Africa here and heads into the Indian Ocean.
- The Maldives. No Maldives island sits on the Equator, but it passes through Maldives waters south of Gaafu Dhaalu Atoll.
- Indonesia. The Equator crosses many Indonesian islands, including Sumatra and Borneo. Indonesia has the longest stretch of the Equator of any country, counting land and sea together.
- Kiribati. Out in the Pacific Ocean, the line passes through Kiribati waters south of Buariki Island.
- Ecuador. The line hits the Galápagos Islands, where two volcanoes on Isabela Island, Volcán Wolf and Volcán Ecuador, sit right on it. Then it crosses mainland Ecuador just north of Quito.
- Colombia. The line crosses the south of the country in the Amazon region.
- Brazil. Our last stop is the Amazon. The Equator runs through the middle of the city of Macapá, near the mouth of the Amazon River, before the line heads back out into the Atlantic.
There is one extra country if you count every bit of sea. The Equator also passes through the waters around Baker Island, a tiny island in the Pacific that belongs to the United States. So some books say 13 countries and some say 14.
Now for a trick question. Does Equatorial Guinea sit on the Equator? No! Despite its name, no part of it touches the line. Its island of Annobón is 155 km south of the Equator, and the rest of the country is to the north. The island country of Nauru, in the Pacific, also misses by a little. It lies between 55 and 62 km south of the line.
Hot Sun and 12-Hour Days at 0° Latitude
Why is it so warm on the Equator? It is all about how the sunlight lands.
At midday on the Equator, the Sun is nearly straight overhead every day of the year. It is never more than about 23° away from the point directly above your head. When sunlight comes straight down, all its energy lands on a small patch of ground. That patch gets very warm.
Near the poles, sunlight arrives at a low slant. The same amount of energy is spread over a much bigger area, so each patch gets less warmth.
In equatorial lowlands, afternoons average about 31 °C (88 °F), and early mornings around 23 °C (73 °F). The temperature hardly changes from January to December. That is why people near the Equator do not really talk about summer and winter. Instead, they often talk about the rainy season and the drier season.
And it rains a lot! Many places on the Equator get between 2,500 and 3,500 mm of rain a year. There are about 200 rainy days a year. All that heat and water is why the Equator is wrapped in rainforests, from the Congo Basin to the Amazon to Borneo.
There is an exception. Somalia sits on the Equator but is dry. A cold ocean current along its coast, the Somali Current, and the pattern of the Asian monsoon keep much of the rain away.
What about day and night? Near the poles, summer days can last for weeks, and winter nights can too. On the Equator, the Sun rises at about 6 in the morning and sets at about 6 in the evening all year round. Daylight is about 14 minutes longer than night, because the air bends sunlight a little and we count sunrise from the moment the top of the Sun peeps over the horizon.
The Equator spins fast, too. Because it is the widest part of the Earth, a spot on the Equator travels about 460 metres every second as the planet turns. That is why rockets like to launch from near the Equator. Europe's spaceport is at Kourou in French Guiana, in South America, not far north of the line. The extra spin gives a rocket a free push and saves fuel.
Snow on the Equator: Cayambe and Mount Kenya
In Ecuador, the volcano Cayambe rises to 5,790 m (18,996 ft). The Equator crosses its southern slope at 4,690 m (15,387 ft). That spot is the highest point anywhere on the Equator. It is also the only place on the whole line where snow lies on the ground.
In Kenya, Mount Kenya stands just south of the line. Its highest peak, Batian, reaches 5,199 m. The ground near the top freezes every night and thaws every morning.
Mitad del Mundo and the Other Equator Monuments
The best-known monument is in Ecuador. The country's name is simply the Spanish word for equator. About 26 km north of the capital, Quito, is a park called Ciudad Mitad del Mundo, which means Middle of the World City. In the middle stands a stone monument 30 m (98 ft) tall, built between 1979 and 1982. A globe 4.5 m wide, weighing 5 tonnes, sits on top. A yellow line runs down the staircase and across the square to show where the Equator is.
The monument honours a team of French scientists who arrived in 1736: Louis Godin, Pierre Bouguer and Charles Marie de La Condamine. They measured the shape of the Earth and helped prove that it bulges at the middle. Modern GPS shows the real Equator is about 240 m north of the painted line!
In Indonesia, the city of Pontianak, on the island of Borneo, has the Tugu Khatulistiwa, or Equator Monument, beside the Kapuas River. The first version went up in 1928. Today the original posts sit inside a dome, with a copy five times bigger outside, opened on 21 September 1991. The Equator has shifted a little since it was built, so there is a newer line nearby marking where it was measured in 2005.
In Brazil, people in Macapá call their home the capital of the middle of the world, because the line runs right through the city. In Kenya and Uganda, roadside signs at Nanyuki and Kayabwe mark the spot so travellers can take a photo.
The Water-Swirl Trick at Nanyuki: Myth Busted
If you visit the Equator sign at Nanyuki, or the Intiñan Museum near Mitad del Mundo, someone may show you a trick. They fill a basin with water and pull the plug. A few steps north, the water swirls one way. A few steps south, it swirls the other way. Right on the line, it drains straight down. Magic?
Not really. The idea comes from something real called the Coriolis effect. Because the Earth spins, huge things that move over long distances, like hurricanes and ocean currents, curve one way in the north and the other way in the south. That is why hurricanes in the north spin anticlockwise and cyclones in the south spin clockwise.
But a sink is tiny. The Coriolis push on a basin of water is far too weak to matter. The shape of the basin, the way it was filled, and how the person pours or turns it are much stronger. Scientists have found that identical toilets drain the same way in the north and in the south, because the shape of the bowl decides it. In 1962, a scientist named Ascher Shapiro at MIT did manage to show the effect. He used a covered tank of water 2 m wide and waited at least a full day for the water to stop moving first.
Now you know where the line runs, why it is warm, and which tricks to watch out for. To see how the Equator fits with the other lines on a map, read our guide to latitude and longitude for kids, find out more about the halves of the planet in hemispheres for kids, or take a closer look at every country on the line in countries that straddle the Equator.