equator
American Heritage Dictionary:
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e·qua·tor
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| equator |
| (Jerry Malone) |
n.
- The imaginary great circle around the earth's surface, equidistant from the poles and perpendicular to the earth's axis of rotation. It divides the earth into the Northern Hemisphere and the Southern Hemisphere.
- A similar great circle drawn on the surface of a celestial body at right angles to the axis of rotation.
- The celestial equator.
- A circle that divides a sphere or other surface into congruent parts.
[Middle English, from Medieval Latin aequātor (diēī et noctis), equalizer (of day and night), from Latin aequāre, to equalize. See equate.]
Wiley Book of Astronomy:
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equator
The great circle on the surface of a body formed by the intersection of the surface with the plane passing through the center of the body perpendicular to the axis of rotation.
Britannica Concise Encyclopedia:
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Equator
Great circle around the Earth that is everywhere equidistant from the geographic poles and lies in a plane perpendicular to the Earth's axis. This geographic, or terrestrial, Equator divides the Earth into the Northern and Southern Hemispheres and forms the imaginary reference line on the Earth's surface from which latitude is reckoned (i.e., 0 latitude). In astronomy, the celestial equator is the great circle in which the plane of the terrestrial Equator intersects the celestial sphere; it is thus equidistant from the celestial poles. When the Sun lies in its plane, day and night are everywhere of equal length; this happens at the equinoxes.
For more information on Equator, visit Britannica.com.
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The great circle around the Earth, equally distant from the North and South poles, which divides the Earth into Northern and Southern hemispheres. It is the greatest circumference of the Earth because of centrifugal force from rotation, and resultant flattening of the polar areas.
The Earth's rotational axis is vertical to the plane of the Equator, and because the inclination of the axis is 66½° from the plane of the ecliptic, the plane of the Equator is always inclined 23½° from the ecliptic.
The celestial equator in astronomy is equally distant from the celestial poles and is the great circle in which the plane of the terrestrial Equator intersects the celestial sphere. See also Astronomy; Mathematical geography.
Oxford Dictionary of Geography:
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equator
The imaginary great circle around the world at latitude 0°. The equator is equidistant between the North and South Poles. It has a length of 40 076 km: about 25000 miles.
Columbia Encyclopedia:
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equator
equator, imaginary great circle around the earth, everywhere equidistant from the two geographical poles and forming the base line from which latitude is reckoned. The equator, which measures c.24,902 mi (40,076 km), is designated as lat. 0°. It intersects N South America, central Africa, and Indonesia. The celestial equator is the projection of the plane of the earth's equator on the celestial sphere (see equatorial coordinate system).
Word Tutor:
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equator
IN BRIEF: An imaginary line around the middle of the Earth that is the same distance from the North Pole and South Pole.
The weather tends to be warmer the closer to the equator you are.
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Sign Language Videos:
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equator
sign description: Three signs are combined to form this word. EARTH + BALL + ROUND.
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The great circle on the surface of the earth whose plane is at right angles to the earth’s axis of rotation. The equator lies in an east-west direction and divides the earth into Northern and Southern Hemispheres. It is normal to the polar axis and equidistant to the poles.
Random House Word Menu:
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categories related to 'equator'
- Maps and Cartography - equator: line of latitude halfway between North and South poles at zero degrees
- Forecasting and Meteorology - equator: great circle of Earth, equidistant from two poles, dividing surface into northern and southern hemispheres
See crossword solutions for the clue Wikipedia on Answers.com:
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Equator
For other uses, see Equator (disambiguation).
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This article includes a list of references, related reading or external links, but its sources remain unclear because it lacks inline citations. Please improve this article by introducing more precise citations. (December 2010) |
0°
Equator
An equator is the intersection of a sphere's surface with the plane perpendicular to the sphere's axis of rotation and containing the sphere's center of mass.
The Equator refers to the Earth's equator and is an imaginary line on the Earth's surface equidistant from the North Pole and South Pole, dividing the Earth into the Northern Hemisphere and Southern Hemisphere. Other planets and spherical astronomical bodies have equators similarly defined.
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Contents
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Geodesy of the equator
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Left: A monument marking the Equator near the town of Pontianak, Indonesia
Right: Road sign marking the Equator near Nanyuki, Kenya |
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The latitude of the Equator is 0° (zero degrees). The Equator is one of the five notable circles of latitude on Earth, with the others being the two Polar Circles and the two Tropical Circles: the Tropic of Cancer and the Tropic of Capricorn. The Equator is the only line of latitude which is also a great circle. The imaginary circle obtained when the Earth's equator is projected onto the sky is called the celestial equator.
The Sun, in its seasonal apparent movement across the sky, passes directly over the Equator twice each year, at the March and September equinoxes. At the Equator, the rays of the sun are perpendicular to the surface of the earth on these dates.
Places on the Equator experience the quickest rates of sunrise and sunset in the world. They are also the only places in the world where the sun can go directly from the zenith to the nadir and from the nadir to the zenith. Such places also have a theoretical constant 12 hours of day and night throughout the year, though in practice there are variations of a few minutes due to the effects of atmospheric refraction and because sunrise and sunset are measured from the time that the edge of the Sun's disk is on the horizon, rather than the center of the disk.
The Earth bulges slightly at the Equator. It has an average diameter of 12,750 kilometres (7,922 mi), but at the Equator the diameter is approximately 43 kilometres (27 mi) greater than the polar diameter.
Locations near the Equator are theoretically good sites for spaceports, such as the Guiana Space Centre in Kourou, French Guiana, as they are already moving faster than any other point on the Earth due to the Earth's rotation, and the added velocity reduces the amount of fuel needed to launch spacecraft. Spacecraft launched in this manner must launch to the east, southeast, or northeast to take advantage of this effect.
For high precision work, the Equator is not quite as fixed as the above discussion implies. The true equatorial plane must always be perpendicular to the Earth's spin axis. Although this axis is relatively stable, its position drifts about 9.0 metres (30 ft) north-south over the course of a year. Thus, the true equator moves slightly, but this effect is only relevant in extremely precise geophysical measurements.
Equatorial seasons and climate
Main article: Tropics
Near the Equator there is little distinction between summer, winter, autumn, or spring. The temperatures there are usually high year-round—with the distinct exception of parts of the Equator that cross high mountains in South America and in Africa. (See Andes Mountains and Mt. Kilimanjaro.) The temperature at the Equator can also plummet during the extensive rainstorms in many locations. In many tropical regions people identify two seasons: the wet season and the dry season. However, many places close to the Equator are on the oceans or rainy throughout the year. The seasons can vary depending on a variety of factors including elevation and proximity to an ocean. These oceanic, rainy, and mountainous locations mean that the equatorial climate is not the hottest in the world.
The surface of the Earth at the Equator lies mostly on three of the oceans: the Pacific Ocean, the Atlantic Ocean, and the Indian Ocean. The highest point on the Equator is at the elevation of 4,690 metres (15,387 ft), at 0°0′0″N 77°59′31″W / 0°N 77.99194°W, found on the southern slopes of Volcán Cayambe [summit 5,790 metres (18,996 ft)] in Ecuador. This place is a short distance above the snow line, and this immediate vicinity forms the only section of the Equator where snow lies on the ground year-round.
Equatorial countries and territories
The Equator traverses the land and/or territorial waters of 14 countries. Starting at the Prime Meridian and heading eastwards, the Equator passes through:
Despite its name, no part of Equatorial Guinea's territory lies on the Equator. However, its island of Annobón is 155 kilometres (100 mi) south of the Equator, and the rest of the country lies to the north.
Crossing the equator
Main article: Line-crossing ceremony
Certain navies, such as the Royal Navy and the US Navy, have a tradition of holding ceremonies on board ship to mark sailors' first crossing of the Equator. These rites of initiation have in the past been notorious for their brutality. Milder line-crossing ceremonies, typically featuring King Neptune, are also held for passengers' entertainment on some civilian ocean liners and cruise ships.
Exact length of the equator
In two widely used geodetic standards, the Equator is modeled as a circle whose radius is a whole number of metres. In 1976 the IAU standardized this radius as 6,378.140 kilometres (3,963 mi), subsequently refined by the IUGG to 6,378.137 kilometres (3,963 mi) and adopted in WGS-84, though the yet more recent IAU-2000 has retained the old IAU-1976 value. In either case, the length of the Equator is by definition exactly 2π times the given standard, which to the nearest millimeter is 40,075.016686 kilometres (24,901.460897 mi) in WGS-84 and 40,075.035535 kilometres (24,901.472609 mi) in IAU-1976 and IAU-2000. Although millimeter precision can be important up to the scale of a mile, it has negligible physical significance at the scale of a geographic feature such as the Equator.
The geographical mile is defined as one arc minute of the Equator, and therefore has different values depending on which standard equator is used, namely 1,855.3248 metres (6,087.024 ft) or 1,855.3257 metres (6,087.027 ft) for respectively WGS-84 and IAU-2000, a difference of nearly a millimeter.
The earth is modeled commonly as a sphere flattened 0.336% along its axis. This makes the Equator 0.16% longer than a meridian (as a great circle passing through the two poles). The IUGG standard meridian is, to the nearest millimeter, 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 (10 ft) short of the geographical mile.
The sea-level surface of the Earth (the geoid) is irregular, so the actual length of the 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 deg West to 169 East to be 1000 feet greater than its "diameter" ninety degrees away.[citation needed]
Climate
The zone of the Equator has a tropical rainforest climate, also known as an equatorial climate. Usually, its average annual temperature is around 30 °C (86 °F) during the day and 23 °C (73 °F) at night. Rainfall is very high, usually from 2,500 to 3,500 mm per year. Average precipitation days are around 200 per year and average sunshine hours are around 2000 per year.
| Climate data for Macapá, 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 (86.0) |
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 (82.0) |
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) |
| Precipitation 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 (101.24) |
| Avg. precipitation 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 (UN)[1], Hong Kong Observatory[2] | |||||||||||||
| Climate data for 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 (90.0) |
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 (81.0) |
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 (73.0) |
22.6 (72.7) |
22.4 (72.3) |
22.7 (72.9) |
| Precipitation 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) |
| Avg. precipitation days (≥ 0.1 mm) | 15 | 13 | 21 | 22 | 20 | 18 | 16 | 25 | 14 | 27 | 25 | 22 | 238 |
| Source: World Meteorological Organization (UN)[3] | |||||||||||||
| Climate data for Libreville, 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 (86.0) |
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 (75.0) |
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) |
| Precipitation 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 (111.878) |
| Avg. precipitation 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 (UN)[4], Hong Kong Observatory[5] | |||||||||||||
See also
 |
Wikimedia Commons has media related to: Equator |
- 1st parallel north
- 1st parallel south
- Antarctic Circle
- Arctic Circle
- Coriolis Effect
- Intertropical Convergence Zone
- Thermal equator
- Tropic of Cancer
- Tropic of Capricorn
- Prime Meridian
Notes
- ^ "Weather Information for Macapa". http://www.worldweather.org/136/c01071.htm.
- ^ Climatological Information for Macapa, Brazil - Hong Kong Observatory
- ^ "Weather Information for Pontianak". http://www.worldweather.org/043/c00653.htm.
- ^ "Weather Information for Libreville". http://www.worldweather.org/128/c00255.htm.
- ^ Climatological Information for Libreville, Gabon - Hong Kong Observatory
References
- Moritz, H (September 1980). "Geodetic Reference System 1980". Bulletin Géodésique (Berlin: Springer-Verlag) 54 (3): 395–405. Bibcode 1980BGeod..54..395M. doi:10.1007/BF02521480. (IUGG/WGS-84 data)
- Taff, Laurence G (1981). Computational Spherical Astronomy. New York: Wiley. ISBN 0-471-06257-X. OCLC 6532537. (IAU data)
External links
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This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)
Translations:
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Equator
n. - Ækvator
Nederlands (Dutch)
evenaar, equator, middellijn, grote cirkel
Français (French)
n. - équateur, ligne équinoxiale
n. - Äquator
Ελληνική (Greek)
n. - (γεωγρ.) ισημερινός (κύκλος)
Português (Portuguese)
n. - equador (m)
Español (Spanish)
n. - Ecuador, línea ecuatorial, línea equinoccial
Svenska (Swedish)
n. - ekvator
中文（简体）(Chinese (Simplified))
赤道
中文（繁體）(Chinese (Traditional))
n. - 赤道
العربيه (Arabic)
(الاسم) خط الإستواء
עברית (Hebrew)
n. - קו-המשווה, משוון
n. - קו המשווה
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The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.
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Mentioned in
equatorial orbit
(astronomy)
equatorial projection
(mapping)
Northern Hemisphere
(geography)
Fleming, Peter Robert
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