Equator

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The equator is an imaginary line on the Earth's surface equidistant from the North Pole and South Pole. It thus divides the Earth into a Northern Hemisphere and a Southern Hemisphere. The equators of other planets and astronomical bodies are defined analogously.

The latitude of the equator is, by definition, 0°. The length of Earth's equator is about 40,075.0 km, or 24,901.5 miles. The exact length is 40,075,016.6856 m in WGS-84, and 40,075,035.5351 m in IAU-2000.

The equator is one of the five main circles of latitude that are based on the relationship between the Earth's axis of rotation and the plane of the Earth's orbit around the sun. It 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 heavens is called the celestial equator.

The Sun, in its seasonal movement through the sky, passes directly over the equator twice each year, on 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, taking minutes. Such places also have a constant 12 hours of day and night throughout the year, while north or south of the equator day length increasingly varies with the seasons.

The Earth bulges slightly at the equator. It has an average diameter of 12,750 km, but at the equator the diameter is approximately 43 km greater.

Locations near the equator are good sites for spaceports, 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.

Contents 1 Equatorial climate 2 Equatorial countries 3 "Crossing the Line" 4 See also 5 References

[edit] Equatorial climate

Temperatures near the equator are high all year round (except at altitude). In many tropical regions people identify two seasons: wet and dry. However, most places close to the equator are wet throughout the year, and seasons can vary depending on a variety of factors including elevation and proximity to an ocean.

The surface of the Earth at the equator is mainly ocean. The highest point on the equator is 4,690 m, at 00°00′00″S, 77°59′31″W on the south slopes of Volcán Cayambe (summit 5,790 m) in Ecuador. This is a short distance above the snow line, and is the only point on the equator where snow lies on the ground.

[edit] Equatorial countries

The equator traverses the land and/or territorial waters of 13 countries. Starting on the west coast of Africa and moving east, these are:

• São Tomé and Príncipe – passing through Ilhéu das Rolas, an islet in this archipelago
• Gabon
• Republic of the Congo
• Democratic Republic of Congo
• Uganda – including some islets in Lake Victoria
• Kenya
• Somalia
• Maldives – misses every island, passing between Gaafu Dhaalu Atoll and Gnaviyani Atoll
• Indonesia – crosses many islands, most notably Sumatra, Borneo, Sulawesi, and Halmahera
• Kiribati – misses every island, passing between Aranuka and Nonouti Atolls in the Gilbert Islands
• Ecuador (literal translation of its official name is "Republic of the Equator") – including Isabela Island in the Galápagos Islands
• Colombia
• Brazil – including some islands in the mouth of the Amazon River and passing through Macapá, capital of Amapá state

Contrary to its name, no part of Equatorial Guinea lies on the equator.

[edit] "Crossing the Line"

Main article: Line-crossing ceremony

The English-speaking seafaring tradition maintains that all sailors who cross the equator during a nautical voyage must undergo rites of passage and elaborate rituals initiating them into The Solemn Mysteries of the Ancient Order of the Deep. These rituals date back to the Middle Ages, though the current ceremonies are most likely derived from Viking traditions. Those who have never "crossed the line" are derisively referred to as "pollywogs" or simply "slimy wogs". Upon entering the domain of His Royal Majesty, Neptunus Rex, all wogs are subject to various initiation rituals performed by those members of the crew who have made the journey before. Upon completion of the initiation ceremony, the wogs are then known as "trusty Shellbacks". If the crossing of the equator is done at the 180th meridian, the title of "Golden Shellback" is conferred, recognizing the simultaneous entry into the realm of the Golden Dragon. If the crossing occurs at the Greenwich or Prime Meridian, the sailor is considered to be an "Emerald Shellback".^{[citation needed]}

[edit] See also

• Antarctic Circle
• Arctic Circle
• Intertropical Convergence Zone
• Prime Meridian
• Thermal equator
• Tropic of Cancer
• Tropic of Capricorn

[edit] References