Equator

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An equator is the intersection of the surface of a rotating sphere (such as a planet) with the plane perpendicular to the axis of rotation and midway between its poles. On Earth, the Equator
Equator is an imaginary line on the surface, equidistant from the North and South Poles, dividing the Earth
Earth into Northern and Southern Hemispheres. It is about 40,075 kilometres (24,901 mi) long, of which 78.7% lies across water and 21.3% over land.

Contents

1 Overview 2 Geodesy

2.1 Precise location 2.2 Exact length

3 Crossing-the- Equator
Equator ceremonies 4 Equatorial countries and territories 5 Equatorial seasons and climate 6 See also 7 References 8 Sources

Overview[edit]

Left: A monument marking the Equator
Equator near the town of Pontianak, Indonesia Right: Road sign marking the Equator
Equator near Nanyuki, Kenya

The latitude of the Earth's equator is, by definition, 0° (zero degrees) of arc. The Equator
Equator is one of the five notable circles of latitude on Earth; the other four are the two Polar Circles (the Arctic Circle
Arctic Circle and the Antarctic Circle) and the two Tropical Circles (the Tropic of Cancer
Tropic of Cancer and the Tropic of Capricorn). The Equator
Equator is the only line of latitude which is also a great circle — that is, one whose plane passes through the center of the globe. The plane of Earth's equator, when projected outwards to the celestial sphere, defines the celestial equator. In the cycle of Earth's seasons, the plane of the equator passes through the Sun
Sun twice per year: at the March and September equinoxes. To a person on the Earth, the Sun
Sun appears to travel North or South over the Equator
Equator (or the celestial equator) at these times. Light rays from the center of the Sun
Sun are perpendicular to the surface of the Earth
Earth at the point of solar noon on the Equator.

The Equator
Equator marked as it crosses Ilhéu das Rolas, in São Tomé and Príncipe

The Marco Zero monument marking the Equator
Equator in Macapá, Brazil.

Locations on the Equator
Equator experience the quickest sunrises and sunsets, because the sun moves nearly perpendicular to the horizon for most of the year. The length of daylight (sunrise to sunset) is almost constant throughout the year; it is about fourteen minutes longer than nighttime due to atmospheric refraction and the fact that sunrise is begun (or sunset is ended) as the upper edge, not the center, of the Sun's disk crosses the horizon. The Earth
Earth bulges slightly at the Equator; the "average" diameter of the Earth
Earth is 12,750 kilometres (7,922 mi), but the diameter at the Equator
Equator is about 43 kilometres (27 mi) greater than at the poles.[1] Sites near the Equator, such as the Guiana Space Centre
Guiana Space Centre in Kourou, French Guiana, are good locations for spaceports as they have a faster rotational speed than other latitudes; the added velocity reduces the fuel needed to launch spacecraft. Because the Earth
Earth spins to the east, spacecraft must also launch to the east (or to the southeast or northeast) to take advantage of this Earth-boost of speed.[citation needed] Geodesy[edit] Further information: Earth
Earth ellipsoid and Reference ellipsoid Precise location[edit] The precise location of the Equator
Equator is not truly fixed; the true equatorial plane is perpendicular to the Earth's spin axis, which drifts about 9 metres (30 ft) during a year. This effect must be accounted for in detailed geophysical measurements.[citation needed] Exact length[edit] In two widely used geodetic standards, the Equator
Equator is modelled as a circle whose radius is a whole number of metres. In 1976 the IAU chose a radius of 6,378.140 kilometres (3,963.192 mi) (codified as the IAU-1976 value), later refined by the IUGG to 6,378.137 kilometres (3,963.191 mi) and adopted in WGS-84. Despite this change, the yet more recent IAU-2000 retained the old IAU-1976 value. If it were really circular, the length of the Equator
Equator would be exactly 2π times the radius, namely 40,075.036 kilometres (24,901.473 mi). However, due to the effect of the tides on the Earth's surface the actual circumference at the equator is about 40,075.16 kilometres (24,901.55 mi). The geographical mile is defined as one arc minute of the Equator, so it has different values depending on which radius is assumed. For example, by WSG-84, the distance is 1,855.3248 metres (6,087.024 ft), while by IAU-2000, it is 1,855.3257 metres (6,087.027 ft). This is a difference of less than one millimeter over the total distance (approximately 1.86 kilometres (1.16 mi)). The earth is commonly modeled as a sphere flattened 0.336% along its axis. This makes the Equator
Equator 0.16% longer than a meridian (a great circle passing through the two poles). The IUGG standard meridian is, to the nearest millimetre, 40,007.862917 kilometres (24,859.733480 mi), one arc minute of which is 1,852.216 metres (6,076.82 ft), explaining the SI standardization of the nautical mile as 1,852 metres (6,076 ft), more than 3 metres (9.8 ft) less than the geographical mile. The sea-level surface of the Earth
Earth (the geoid) is irregular, so the actual length of the Equator
Equator is not so easy to determine. Aviation Week and Space Technology on 9 October 1961 reported that measurements using the Transit IV-A satellite had shown the equatorial "diameter" from longitude 11° West to 169° East to be 1,000 feet (300 m) greater than its "diameter" ninety degrees away.[citation needed] Crossing-the- Equator
Equator ceremonies[edit] Main article: Line-crossing ceremony Certain navies, such as the Royal Navy, Russian Navy, and US Navy, have a tradition of holding ceremonies aboard ships to mark sailors' first crossing of the Equator. These ceremonial events have in the past been notorious for their brutality.[citation needed] Milder line-crossing ceremonies, typically featuring King Neptune, are also held for passengers' entertainment on some civilian ocean liners and cruise ships.[citation needed] Equatorial countries and territories[edit]

Map all coordinates using: OpenStreetMap · Google Maps

Download coordinates as: KML · GPX

The Equator
Equator passes through the land of 11 countries. Starting at the Prime Meridian
Prime Meridian and heading eastwards, the Equator
Equator passes through:

Co-ordinates Country, territory or sea Notes

0°N 0°E / 0°N 0°E / 0; 0 (Prime Meridian) Atlantic Ocean Gulf of Guinea

0°0′N 6°31′E / 0.000°N 6.517°E / 0.000; 6.517 (São Tomé and Príncipe) São Tomé and Príncipe Ilhéu das Rolas

0°0′N 9°21′E / 0.000°N 9.350°E / 0.000; 9.350 (Gabon) Gabon passes 8.9 km (5.5 mi) south of Ayem, 10.6 km (6.6 mi) north of Mayene, Booue

0°0′N 13°56′E / 0.000°N 13.933°E / 0.000; 13.933 (Republic of the Congo) Republic of the Congo Passing through the town of Makoua.

0°0′N 17°46′E / 0.000°N 17.767°E / 0.000; 17.767 (Democratic Republic of the Congo) Democratic Republic of the Congo Passing 9 km (5.6 mi) south of central Butembo

0°0′N 29°43′E / 0.000°N 29.717°E / 0.000; 29.717 (Uganda) Uganda Passing 32 km (20 mi) south of central Kampala

0°0′N 32°22′E / 0.000°N 32.367°E / 0.000; 32.367 (Lake Victoria) Lake Victoria Passing through some islands of Uganda

0°0′N 34°0′E / 0.000°N 34.000°E / 0.000; 34.000 (Kenya) Kenya Passing 6 km (3.7 mi) north of central Kisumu

0°0′N 41°0′E / 0.000°N 41.000°E / 0.000; 41.000 (Somalia) Somalia

0°0′N 42°53′E / 0.000°N 42.883°E / 0.000; 42.883 (Indian Ocean) Indian Ocean Passing between Huvadhu Atoll
Huvadhu Atoll and Fuvahmulah
Fuvahmulah of the Maldives

0°0′N 98°12′E / 0.000°N 98.200°E / 0.000; 98.200 (Indonesia) Indonesia The Batu Islands, Sumatra
Sumatra and the Lingga Islands

0°0′N 104°34′E / 0.000°N 104.567°E / 0.000; 104.567 (Karimata Strait) Karimata Strait

0°0′N 109°9′E / 0.000°N 109.150°E / 0.000; 109.150 (Indonesia) Indonesia Borneo

0°0′N 117°30′E / 0.000°N 117.500°E / 0.000; 117.500 (Makassar Strait) Makassar Strait

0°0′N 119°40′E / 0.000°N 119.667°E / 0.000; 119.667 (Indonesia) Indonesia Sulawesi
Sulawesi (Celebes)

0°0′N 120°5′E / 0.000°N 120.083°E / 0.000; 120.083 (Gulf of Tomini) Gulf of Tomini

0°0′N 124°0′E / 0.000°N 124.000°E / 0.000; 124.000 (Molucca Sea) Molucca Sea

0°0′N 127°24′E / 0.000°N 127.400°E / 0.000; 127.400 (Indonesia) Indonesia Kayoa and Halmahera
Halmahera islands

0°0′N 127°53′E / 0.000°N 127.883°E / 0.000; 127.883 ( Halmahera
Halmahera Sea) Halmahera
Halmahera Sea

0°0′N 129°20′E / 0.000°N 129.333°E / 0.000; 129.333 (Indonesia) Indonesia Gebe and Kawe islands

0°0′N 129°21′E / 0.000°N 129.350°E / 0.000; 129.350 (Pacific Ocean) Pacific Ocean Passing between Aranuka
Aranuka and Nonouti
Nonouti atolls, Kiribati
Kiribati (at 0°0′N 173°40′E / 0.000°N 173.667°E / 0.000; 173.667)

0°0′N 80°6′W / 0.000°N 80.100°W / 0.000; -80.100 (Ecuador) Ecuador Passing 24 km (15 mi) north of central Quito, near Mitad del Mundo, and precisely at the location of Catequilla, a pre-Columbian ruin Also, Isabela Island in the Galápagos Islands

0°0′N 75°32′W / 0.000°N 75.533°W / 0.000; -75.533 (Colombia) Colombia Passing 4.3 km (2.7 mi) north of the border with Peru

0°0′N 70°3′W / 0.000°N 70.050°W / 0.000; -70.050 (Brazil) Brazil Amazonas Roraima Pará Amapá
Amapá (passing slightly south of the city center of the state capital Macapá)

0°0′N 49°21′W / 0.000°N 49.350°W / 0.000; -49.350 (Atlantic Ocean) Atlantic Ocean At the Perigoso Canal on the mouth of the Amazon River

Despite its name, no part of Equatorial Guinea
Equatorial Guinea lies on the Equator. However, its island of Annobón is 155 km (96 mi) south of the Equator, and the rest of the country lies to the north.

GPS reading taken on the Equator
Equator close to the Quitsato Sundial, at Mitad del Mundo, Ecuador.[2]

Equatorial seasons and climate[edit] Main articles: Seasons, Tropics, and Effect of sun angle on climate

Diagram of the seasons, depicting the situation at the December solstice. Regardless of the time of day (i.e. the Earth’s rotation on its axis), the North Pole
North Pole will be dark, and the South Pole
South Pole will be illuminated; see also arctic winter. In addition to the density of incident light, the dissipation of light in the atmosphere is greater when it falls at a shallow angle.

Seasons
Seasons result from the tilt of the Earth's axis compared to the plane of its revolution around the Sun. Throughout the year the northern and southern hemispheres are alternately turned either toward or away from the sun depending on Earth's position in its orbit. The hemisphere turned toward the sun receives more sunlight and is in summer, while the other hemisphere receives less sun and is in winter (see solstice). At the equinoxes, the Earth's axis is perpendicular to the sun rather than tilted toward or away, meaning that day and night are both about 12 hours long across the whole of the Earth. The Equator
Equator lies mostly on the three largest oceans: the Atlantic Ocean, the Indian Ocean, and the Pacific Ocean. Near the Equator
Equator there is little temperature change throughout the year, though there may be dramatic differences in rainfall and humidity. The terms summer, autumn, winter and spring do not generally apply. Lowlands around the Equator
Equator generally have a tropical rainforest climate, also known as an equatorial climate, though cold currents cause some regions to have tropical monsoon climates with a dry season in the middle of the year, and the Somali Current
Somali Current generated by the Asian monsoon due to continental heating via the high Tibetan Plateau
Tibetan Plateau causes Greater Somalia
Somalia to have an arid climate despite its equatorial location. Average annual temperatures in equatorial lowlands are around 31 °C (88 °F) during the afternoon and 23 °C (73 °F) around sunrise. Rainfall is away from cold current upwelling zones very high, from 2,500 to 3,500 mm (98 to 138 in) per year. There are about 200 rainy days per year and average annual sunshine hours are around 2,000. Despite high year-round sea level temperatures, some higher altitudes such as the Andes
Andes and Mount Kilimanjaro
Mount Kilimanjaro have glaciers. The highest point on the Equator
Equator is at the elevation of 4,690 metres (15,387 ft), at 0°0′0″N 77°59′31″W / 0.00000°N 77.99194°W / 0.00000; -77.99194 (highest point on the Equator), found on the southern slopes of Volcán Cayambe
Volcán Cayambe [summit 5,790 metres (18,996 ft)] in Ecuador. This is slightly above the snow line and is the only place on the Equator
Equator where snow lies on the ground. At the Equator
Equator the snow line is around 1,000 metres (3,280 ft) lower than on Mount Everest
Mount Everest and as much as 2,000 metres (6,560 ft) lower than the highest snow line in the world, near the Tropic of Capricorn on Llullaillaco.

Climate data for Macapá, Brazil
Brazil in South America

Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year

Average high °C (°F) 29.7 (85.5) 29.2 (84.6) 29.3 (84.7) 29.5 (85.1) 30.0 (86) 30.3 (86.5) 30.6 (87.1) 31.5 (88.7) 32.1 (89.8) 32.6 (90.7) 32.3 (90.1) 31.4 (88.5) 30.71 (87.28)

Daily mean °C (°F) 26.4 (79.5) 26.2 (79.2) 26.3 (79.3) 26.5 (79.7) 26.8 (80.2) 26.8 (80.2) 26.8 (80.2) 27.4 (81.3) 27.8 (82) 28.1 (82.6) 27.9 (82.2) 27.4 (81.3) 27.03 (80.65)

Average low °C (°F) 23.0 (73.4) 23.1 (73.6) 23.2 (73.8) 23.5 (74.3) 23.5 (74.3) 23.2 (73.8) 22.9 (73.2) 23.3 (73.9) 23.4 (74.1) 23.5 (74.3) 23.5 (74.3) 23.4 (74.1) 23.29 (73.92)

Average rainfall mm (inches) 299.6 (11.795) 347.0 (13.661) 407.2 (16.031) 384.3 (15.13) 351.5 (13.839) 220.1 (8.665) 184.8 (7.276) 98.00 (3.8583) 42.60 (1.6772) 35.50 (1.3976) 58.40 (2.2992) 142.5 (5.61) 2,571.5 (101.2393)

Average rainy days (≥ 0.1 mm) 23 22 24 24 25 22 19 13 6 5 6 14 203

Mean monthly sunshine hours 148.8 113.1 108.5 114.0 151.9 189.0 226.3 272.8 273.0 282.1 252.0 204.6 2,336.1

Source: World Meteorological Organization
World Meteorological Organization (UN),[3] Hong Kong Observatory[4]

Climate data for Pontianak, Indonesia
Pontianak, Indonesia in Asia

Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year

Average high °C (°F) 32.4 (90.3) 32.7 (90.9) 32.9 (91.2) 33.2 (91.8) 33.0 (91.4) 33.2 (91.8) 32.9 (91.2) 33.4 (92.1) 32.6 (90.7) 32.6 (90.7) 32.2 (90) 32.0 (89.6) 32.7 (90.9)

Daily mean °C (°F) 27.6 (81.7) 27.7 (81.9) 28.0 (82.4) 28.2 (82.8) 28.2 (82.8) 28.2 (82.8) 27.7 (81.9) 27.9 (82.2) 27.6 (81.7) 27.7 (81.9) 27.4 (81.3) 27.2 (81) 27.7 (81.9)

Average low °C (°F) 22.7 (72.9) 22.6 (72.7) 23.0 (73.4) 23.2 (73.8) 23.4 (74.1) 23.1 (73.6) 22.5 (72.5) 22.3 (72.1) 22.6 (72.7) 22.8 (73) 22.6 (72.7) 22.4 (72.3) 22.7 (72.9)

Average rainfall mm (inches) 260 (10.24) 215 (8.46) 254 (10) 292 (11.5) 256 (10.08) 212 (8.35) 201 (7.91) 180 (7.09) 295 (11.61) 329 (12.95) 400 (15.75) 302 (11.89) 3,196 (125.83)

Average rainy days (≥ 0.1 mm) 15 13 21 22 20 18 16 25 14 27 25 22 238

Source: World Meteorological Organization
World Meteorological Organization (UN)[5]

Climate data for Libreville, Gabon
Gabon in Africa

Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year

Average high °C (°F) 29.5 (85.1) 30.0 (86) 30.2 (86.4) 30.1 (86.2) 29.4 (84.9) 27.6 (81.7) 26.4 (79.5) 26.8 (80.2) 27.5 (81.5) 28.0 (82.4) 28.4 (83.1) 29.0 (84.2) 28.58 (83.44)

Daily mean °C (°F) 26.8 (80.2) 27.0 (80.6) 27.1 (80.8) 26.6 (79.9) 26.7 (80.1) 25.4 (77.7) 24.3 (75.7) 24.3 (75.7) 25.4 (77.7) 25.7 (78.3) 25.9 (78.6) 26.2 (79.2) 25.95 (78.71)

Average low °C (°F) 24.1 (75.4) 24.0 (75.2) 23.9 (75) 23.1 (73.6) 24.0 (75.2) 23.2 (73.8) 22.1 (71.8) 21.8 (71.2) 23.2 (73.8) 23.4 (74.1) 23.4 (74.1) 23.4 (74.1) 23.30 (73.94)

Average rainfall mm (inches) 250.3 (9.854) 243.1 (9.571) 363.2 (14.299) 339.0 (13.346) 247.3 (9.736) 54.10 (2.1299) 6.600 (0.25984) 13.70 (0.5394) 104.0 (4.094) 427.2 (16.819) 490.0 (19.291) 303.2 (11.937) 2,841.7 (111.87614)

Average rainy days (≥ 0.1 mm) 17.9 14.8 19.5 19.2 16.0 3.70 1.70 4.90 14.5 25.0 22.6 17.6 177.4

Mean monthly sunshine hours 176.7 182.7 176.7 177.0 158.1 132.0 117.8 89.90 96.00 111.6 135.0 167.4 1,720.9

Source: World Meteorological Organization
World Meteorological Organization (UN),[6] Hong Kong Observatory[7]