Tropic of Cancer

Last updated

Coordinates: 23°26′12.5″N0°0′0″W / 23.436806°N -0.00000°E / 23.436806; -0.00000 (Prime Meridian)

Contents

World map showing the Tropic of Cancer World map with tropic of cancer.svg
World map showing the Tropic of Cancer
Relationship of Earth's axial tilt (e) to the tropical and polar circles Axial tilt vs tropical and polar circles.svg
Relationship of Earth's axial tilt (ε) to the tropical and polar circles

The Tropic of Cancer, which is also referred to as the Northern Tropic, is the most northerly circle of latitude on Earth at which the Sun can be directly overhead. This occurs on the June solstice, when the Northern Hemisphere is tilted toward the Sun to its maximum extent. [1] It also reaches 90 degrees below the horizon at solar midnight on the December Solstice. Using a continuously updated formula, the circle is currently 23°26′11.1″ (or 23.43641°) north of the Equator.

Its Southern Hemisphere counterpart, marking the most southerly position at which the Sun can be directly overhead, is the Tropic of Capricorn. These tropics are two of the five major circles of latitude that mark maps of Earth, the others being the Arctic and Antarctic circles and the Equator. The positions of these two circles of latitude (relative to the Equator) are dictated by the tilt of Earth's axis of rotation relative to the plane of its orbit, and since the tilt changes, the location of these two circles also changes.

In geopolitics, it is known for being the southern limitation on the mutual defence obligation of NATO, as member states of NATO are not obligated to come to the defence of territory below the Tropic of Cancer.

Name

When this line of latitude was named in the last centuries BC, the Sun was in the constellation Cancer (Latin for crab ) at the June solstice, the time each year that the Sun reaches its zenith at this latitude. Due to the precession of the equinoxes, this is no longer the case; today the Sun is in Taurus at the June solstice. The word "tropic" itself comes from the Greek "trope (τροπή)", meaning turn (change of direction, or circumstances), inclination, referring to the fact that the Sun appears to "turn back" at the solstices.

Drift

Carretera 83 (Via Corta) Zaragoza-Victoria, km 27+800. Of the Tropic of Cancer's intersections with Mexican federal highways, this is the only one where it is precisely marked and the drift from 2005 to 2010 can be seen. Tropico de Cancer en Mexico - Carretera 83 (Via Corta) Zaragoza-Victoria, Km 27+800.jpg
Carretera 83 (Vía Corta) Zaragoza-Victoria, km 27+800. Of the Tropic of Cancer's intersections with Mexican federal highways, this is the only one where it is precisely marked and the drift from 2005 to 2010 can be seen.

The Tropic of Cancer's position is not fixed, but constantly changes because of a slight wobble in the Earth's longitudinal alignment relative to the ecliptic, the plane in which the Earth orbits around the Sun. Earth's axial tilt varies over a 41,000-year period from 22.1 to 24.5 degrees, and as of 2000 is about 23.4 degrees, which will continue to remain valid for about a millennium. This wobble means that the Tropic of Cancer is currently drifting southward at a rate of almost half an arcsecond (0.468″) of latitude, or 15 m (49 ft), per year. The circle's position was at exactly 23° 27′N in 1917 and will be at 23° 26'N in 2045. [2] The distance between the Antarctic Circle and the Tropic of Cancer is essentially constant as they move in tandem. This is based on an assumption of a constant equator, but the precise location of the equator is not truly fixed. See equator, axial tilt and circles of latitude for additional details.

Geography

Map all coordinates using: OpenStreetMap  
Download coordinates as: KML

North of the tropic are the subtropics and the North Temperate Zone. The equivalent line of latitude south of the Equator is called the Tropic of Capricorn, and the region between the two, centered on the Equator, is the tropics.

In the year 2000, more than half of the world's population lived north of the Tropic of Cancer. [3]

There are approximately 13 hours, 35 minutes of daylight during the summer solstice. During the winter solstice, there are 10 hours, 41 minutes of daylight.

Using 23°26'N for the Tropic of Cancer, the tropic passes through the following countries and territories starting at the prime meridian and heading eastward:

Co-ordinatesCountry, territory or seaNotes
23°26′N0°0′E / 23.433°N 0.000°E / 23.433; 0.000 (Prime Meridian) Flag of Algeria.svg  Algeria
23°26′N11°51′E / 23.433°N 11.850°E / 23.433; 11.850 (Niger) Flag of Niger.svg  Niger
23°26′N12°17′E / 23.433°N 12.283°E / 23.433; 12.283 (Libya) Flag of Libya.svg  Libya The Tropic touches on the northernmost point of Flag of Chad.svg  Chad at 23°26′N15°59′E / 23.433°N 15.983°E / 23.433; 15.983 (Northernmost point of Chad)
23°26′N25°0′E / 23.433°N 25.000°E / 23.433; 25.000 (Egypt) Flag of Egypt.svg  Egypt The Tropic passes through Lake Nasser
23°26′N35°30′E / 23.433°N 35.500°E / 23.433; 35.500 (Red Sea) Red Sea
23°26′N38°38′E / 23.433°N 38.633°E / 23.433; 38.633 (Saudi Arabia) Flag of Saudi Arabia.svg  Saudi Arabia
23°26′N52°10′E / 23.433°N 52.167°E / 23.433; 52.167 (United Arab Emirates) Flag of the United Arab Emirates.svg  United Arab Emirates Abu Dhabi emirate only
23°26′N55°24′E / 23.433°N 55.400°E / 23.433; 55.400 (Oman) Flag of Oman.svg  Oman The tropic crosses Muscat, the country's capital.
23°26′N58°46′E / 23.433°N 58.767°E / 23.433; 58.767 (Indian Ocean) Indian Ocean Arabian Sea
23°26′N68°23′E / 23.433°N 68.383°E / 23.433; 68.383 (India) Flag of India.svg  India States of Gujarat, Rajasthan, Madhya Pradesh, Chhattisgarh, Jharkhand and West Bengal
23°26′N88°47′E / 23.433°N 88.783°E / 23.433; 88.783 (Bangladesh) Flag of Bangladesh.svg  Bangladesh Khulna, Dhaka, and Chittagong divisions
23°26′N91°14′E / 23.433°N 91.233°E / 23.433; 91.233 (India) Flag of India.svg  India State of Tripura
23°26′N91°56′E / 23.433°N 91.933°E / 23.433; 91.933 (Bangladesh) Flag of Bangladesh.svg  Bangladesh Chittagong Division
23°26′N92°19′E / 23.433°N 92.317°E / 23.433; 92.317 (India) Flag of India.svg  India State of Mizoram
23°26′N93°23′E / 23.433°N 93.383°E / 23.433; 93.383 (Myanmar) Flag of Myanmar.svg  Myanmar Chin State, Sagaing Division, Mandalay Division, Shan State
23°26′N98°54′E / 23.433°N 98.900°E / 23.433; 98.900 (China) Flag of the People's Republic of China.svg  China Provinces of Yunnan (passing about 7 km north of the border with Flag of Vietnam.svg  Vietnam), Guangxi, and Guangdong
23°26′N117°8′E / 23.433°N 117.133°E / 23.433; 117.133 (Taiwan Strait) Taiwan Strait
23°26′N120°8′E / 23.433°N 120.133°E / 23.433; 120.133 (Taiwan) Flag of the Republic of China.svg  Taiwan Hujing Island (Huching Island), Chiayi County, Hualien County
23°26′N121°29′E / 23.433°N 121.483°E / 23.433; 121.483 (Philippine Sea) Philippine Sea
23°26′N142°00′E / 23.433°N 142.000°E / 23.433; 142.000 (Pacific Ocean) Pacific Ocean Passing just south of Necker Island, Hawaii, Flag of the United States.svg  United States
23°26′N110°15′W / 23.433°N 110.250°W / 23.433; -110.250 (Mexico) Flag of Mexico.svg  Mexico State of Baja California Sur
23°26′N109°24′W / 23.433°N 109.400°W / 23.433; -109.400 (Gulf of California) Gulf of California
23°26′N106°35′W / 23.433°N 106.583°W / 23.433; -106.583 (Mexico) Flag of Mexico.svg  Mexico States of Sinaloa, Durango, Zacatecas, San Luis Potosí, Nuevo León, and Tamaulipas
23°26′N97°45′W / 23.433°N 97.750°W / 23.433; -97.750 (Gulf of Mexico) Gulf of Mexico Passing just north of Cuba
23°26′N83°0′W / 23.433°N 83.000°W / 23.433; -83.000 (Atlantic Ocean) Atlantic Ocean Passing through the Straits of Florida and the Nicholas Channel
Passing just south of the Anguilla Cays (Flag of the Bahamas.svg  Bahamas)
Passing through the Santaren Channel and into the open ocean
23°26′N76°0′W / 23.433°N 76.000°W / 23.433; -76.000 (Bahamas) Flag of the Bahamas.svg  Bahamas Exuma Islands and Long Island
23°26′N75°10′W / 23.433°N 75.167°W / 23.433; -75.167 (Atlantic Ocean) Atlantic Ocean
23°26′N15°57′W / 23.433°N 15.950°W / 23.433; -15.950 (Western Sahara) Western Sahara Claimed by Flag of Morocco.svg  Morocco and the Flag of the Sahrawi Arab Democratic Republic.svg  Sahrawi Arab Democratic Republic
23°26′N12°0′W / 23.433°N 12.000°W / 23.433; -12.000 (Mauritania) Flag of Mauritania.svg  Mauritania
23°26′N6°23′W / 23.433°N 6.383°W / 23.433; -6.383 (Mali) Flag of Mali.svg  Mali
23°26′N2°23′W / 23.433°N 2.383°W / 23.433; -2.383 (Algeria) Flag of Algeria.svg  Algeria

Climate

The climate at the Tropic of Cancer is generally hot and dry, except for cooler highland regions in China and easterly coastal areas, where orographic rainfall can be very heavy, in some places reaching 4 metres (160 in) annually. Most regions on the Tropic of Cancer experience two distinct seasons: an extremely hot summer with temperatures often reaching 45 °C (113 °F) and a warm winter with maxima around 22 °C (72 °F). Much land on or near the Tropic of Cancer is part of the Sahara Desert, while to the east, the climate is torrid monsoonal with a short wet season from June to September, and very little rainfall for the rest of the year.

The highest mountain on or adjacent to the Tropic of Cancer is Yu Shan in Taiwan; though it had glaciers descending as low as 2,800 metres (9,190 ft) during the Last Glacial Maximum, none survive and at present no glaciers exist within 470 kilometres (290 mi) of the Tropic of Cancer; the nearest currently surviving are the Minyong and Baishui in the Himalayas to the north and on Iztaccíhuatl to the south.

Circumnavigation

According to the rules of the Fédération Aéronautique Internationale, for a flight to compete for a round-the-world speed record, it must cover a distance no less than the length of the Tropic of Cancer, cross all meridians, and end on the same airfield where it started.

Length of the Tropic of Cancer at 23°26′11.7″N is 36,788 km (22,859 mi). [4]

For an ordinary circumnavigation the rules are somewhat relaxed and the distance is set to a rounded value of at least 36,770 kilometres (22,850 mi).

See also

Related Research Articles

Latitude Geographic coordinate specifying north–south position

In geography, latitude is a geographic coordinate that specifies the north–south position of a point on the Earth's surface. Latitude is an angle which ranges from 0° at the Equator to 90° at the poles. Lines of constant latitude, or parallels, run east–west as circles parallel to the equator. Latitude is used together with longitude to specify the precise location of features on the surface of the Earth. On its own, the term latitude should be taken to be the geodetic latitude as defined below. Briefly, geodetic latitude at a point is the angle formed by the vector perpendicular to the ellipsoidal surface from that point, and the equatorial plane. Also defined are six auxiliary latitudes that are used in special applications.

Northern Hemisphere Half of Earth that is north of the Equator

The Northern Hemisphere is the half of Earth that is north of the Equator. For other planets in the Solar System, north is defined as being in the same celestial hemisphere relative to the invariable plane of the solar system as Earth's North Pole.

A solstice is an event that occurs when the Sun appears to reach its most northerly or southerly excursion relative to the celestial equator on the celestial sphere. Two solstices occur annually, around June 21 and December 21. In many countries, the seasons of the year are determined by reference to the solstices and the equinoxes.

Tropic of Capricorn Line of southernmost latitude at which the sun can be directly overhead

The Tropic of Capricorn is the circle of latitude that contains the subsolar point at the December solstice. It is thus the southernmost latitude where the Sun can be seen directly overhead. It also reaches 90 degrees below the horizon at solar midnight on the June Solstice. Its northern equivalent is the Tropic of Cancer.

Analemma Diagrammatic representation of suns position over a period of time

In astronomy, an analemma is a diagram showing the position of the Sun in the sky as seen from a fixed location on Earth at the same mean solar time, as that position varies over the course of a year. The diagram will resemble a figure eight. Globes of Earth often display an analemma as a two-dimensional figure of equation of time vs. declination of the Sun.

Circle of latitude Geographic notion

A circle of latitude or line of latitude on Earth is an abstract east–west small circle connecting all locations around Earth at a given latitude coordinate line.

Polar circle

A polar circle is a geographic term for a conditional circular line (arc) referring either to the Arctic Circle or the Antarctic Circle. These are two of the keynote circles of latitude (parallels). On Earth, the Arctic Circle is currently drifting northwards at a speed of about 14.5 m per year and is now at a mean latitude of 66°33′48.9″ N; the Antarctic Circle is currently drifting southwards at a speed of about 14.5 m per year and is now at a mean latitude of 66°33′48.9″ S. Polar circles are often equated with polar regions of Earth. Due to their inherent climate environment, the bulk of the Arctic Circle, much of which is sea, is sparsely settled whereas this applies to all of Antarctica which is mainly land and sheltered ice shelves.

Thermal equator

The thermal equator is a belt encircling Earth, defined by the set of locations having the highest mean annual temperature at each longitude around the globe. Because local temperatures are sensitive to the geography of a region, mountain ranges and ocean currents ensure that smooth temperature gradients are impossible, the location of the thermal equator is not identical to that of the geographic Equator.

Middle latitudes Spatial region on Earth

The middle latitudes are a spatial region on Earth located between the latitudes 23°26'22" and 66°33'39" north, and 23°26'22" and 66°33'39" south. They include Earth's subtropical and temperate zones, which lie between the tropics and the polar circles. Weather fronts and extratropical cyclones are usually found in this area, as well as occasional tropical cyclones, which have traveled from their areas of formation closer to the Equator.

Subsolar point Point which the sun is directly overhead

The subsolar point on a planet is the point at which its sun is perceived to be directly overhead ; that is, where the sun's rays strike the planet exactly perpendicular to its surface. It can also mean the point closest to the sun on an astronomical object, even though the sun might not be visible.

A lunar standstill or lunistice is when the moon reaches its furthest north or furthest south point during the course of a month. The declination at lunar standstill varies in a cycle 18.6 years long between 18.134° and 28.725°, due to lunar precession. These extremes are called the minor and major lunar standstills.

Geographical zone Major regions of Earths surface demarcated by latitude

The five main latitude regions of Earth's surface comprise geographical zones, divided by the major circles of latitude. The differences between them relate to climate. They are as follows:

  1. The North Frigid Zone, between the North Pole at 90° N and the Arctic Circle at 66°33′48.7" N, covers 4.12% of Earth's surface.
  2. The North Temperate Zone, between the Arctic Circle at 66°33′48.7" N and the Tropic of Cancer at 23°26'11.3" N, covers 25.99% of Earth's surface.
  3. The Torrid Zone, between the Tropic of Cancer at 23°26'11.3" N and the Tropic of Capricorn at 23°26'11.3" S, covers 39.78% of Earth's surface.
  4. The South Temperate Zone, between the Tropic of Capricorn at 23°26'11.3" S and the Antarctic Circle at 66°33'48.7" S, covers 25.99% of Earth's surface.
  5. The South Frigid Zone, from the Antarctic Circle at 66°33'48.7" S and the South Pole at 90° S, covers 4.12% of Earth's surface.
Daytime Period of a day in which a location experiences natural illumination

Daytime as observed on Earth is the period of the day during which a given location experiences natural illumination from direct sunlight. Daytime occurs when the Sun appears above the local horizon, that is, anywhere on the globe's hemisphere facing the Sun. In direct sunlight the movement of the sun can be recorded and observed using a sundial that casts a shadow that slowly moves during the day. Other planets and natural satellites that rotate relative to a luminous primary body, such as a local star, also experience daytime, but this article primarily discusses daytime on Earth.

Summer solstice Astronomical phenomenon

The summer solstice, also known as estival solstice or midsummer, occurs when one of Earth's poles has its maximum tilt toward the Sun. It happens twice yearly, once in each hemisphere. For that hemisphere, the summer solstice is when the Sun reaches its highest position in the sky and is the day with the longest period of daylight. Within the Arctic circle or Antarctic circle, there is continuous daylight around the summer solstice. On the summer solstice, Earth's maximum axial tilt toward the Sun is 23.44°. Likewise, the Sun's declination from the celestial equator is 23.44°.

Sun path Arc-like path that the Sun appears to follow across the sky

Sun path, sometimes also called day arc, refers to the daily and seasonal arc-like path that the Sun appears to follow across the sky as the Earth rotates and orbits the Sun. The Sun's path affects the length of daytime experienced and amount of daylight received along a certain latitude during a given season.

Equator Circle of latitude that divides the Earth into northern and southern hemispheres

The Equator is a circle of latitude, about 40,075 km (24,901 mi) in circumference, that divides Earth into the Northern and Southern hemispheres. It is an imaginary line located at 0 degrees latitude, halfway between the North and South poles.

23rd parallel north Circle of latitude

The 23rd parallel north is a circle of latitude that is 23 degrees north of the Earth's equatorial plane, about 50 kilometres (31 mi) south of the Tropic of Cancer. It crosses Africa, Asia, the Indian Ocean, the Pacific Ocean, North America, the Caribbean and the Atlantic Ocean.

The solar equator is the latitude on Earth at which the Sun is observed directly overhead at midday. Due to the obliquity of Earth's axis, the solar equator varies during the year, from the Tropic of Capricorn on the December solstice to the Tropic of Cancer on the June solstice. On the day of either equinox, the Sun's position is at the zenith when viewed from the geographic equator. The Sun can never be observed directly overhead from outside of the tropics.

Antarctic Circle Boundary of the Antarctic

The Antarctic Circle is the most southerly of the five major circles of latitude that mark maps of Earth. The region south of this circle is known as the Antarctic, and the zone immediately to the north is called the Southern Temperate Zone. South of the Antarctic Circle, the Sun is above the horizon for 24 continuous hours at least once per year and the centre of the Sun is below the horizon for 24 continuous hours at least once per year ; this is also true within the equivalent polar circle in the Northern Hemisphere, the Arctic Circle.

Arctic Circle Boundary of the Arctic

The Arctic Circle is one of the two polar circles and the most northerly of the five major circles of latitude as shown on maps of Earth. It marks the northernmost point at which the center of the noon sun is just visible on the December solstice and the southernmost point at which the center of the midnight sun is just visible on the June solstice. The region north of this circle is known as the Arctic, and the zone just to the south is called the Northern Temperate Zone.

References

  1. "PHP Science Labs" . Retrieved 2014-01-01.
  2. Montana State University: Milankovitch Cycles & Glaciation  Archived August 6, 2011, at the Wayback Machine
  3. Quigley, Robert. "The World's Population Mapped by Latitude and Longitude". The Mary Sue. Retrieved 11 January 2021.
  4. RhumbSolve online rhumb line calculator.