Tropic of Cancer: Difference between revisions
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[[File:axial_tilt_vs_tropical_and_polar_circles.svg|thumb|350px|Relationship of Earth's axial tilt (ε) to the tropical and polar circles]] | [[File:axial_tilt_vs_tropical_and_polar_circles.svg|thumb|350px|Relationship of Earth's axial tilt (ε) to the tropical and polar circles]] | ||
The '''Tropic of Cancer''', also known as the '''Northern Tropic''', is the [[Earth]]'s northernmost [[circle of latitude]] where the [[Sun]] can be seen [[subsolar point|directly overhead]]. This occurs on the [[June solstice]], when the [[Northern Hemisphere]] is tilted toward the Sun to its maximum extent.<ref>{{cite web|title=Obliquity of the Ecliptic and Arctic Circle Calculator|url=https://www.phpsciencelabs.com/obliquity-of-the-ecliptic-calculator/|access-date=September 20, 2022}}</ref> It also reaches 90 degrees below the horizon at solar midnight on the [[December solstice]]. Using a continuously updated formula, the circle is currently {{circle of latitude|tropical|convert}} north of the [[Equator]]. | The '''Tropic of Cancer''', also known as the '''Northern Tropic''',{{cn|date=September 2025}} is the [[Earth]]'s northernmost [[circle of latitude]] where the [[Sun]] can be seen [[subsolar point|directly overhead]]. This occurs on the [[June solstice]], when the [[Northern Hemisphere]] is tilted toward the Sun to its maximum extent.<ref>{{cite web|title=Obliquity of the Ecliptic and Arctic Circle Calculator|url=https://www.phpsciencelabs.com/obliquity-of-the-ecliptic-calculator/|access-date=September 20, 2022}}</ref> It also reaches 90 degrees below the horizon at solar midnight on the [[December solstice]]. Using a continuously updated formula, the circle is currently {{circle of latitude|tropical|convert}} north of the [[Equator]]. | ||
Its [[Southern Hemisphere]] counterpart, marking the most southerly position at which the Sun can be seen directly overhead, is the [[Tropic of Capricorn]]. These tropics are two of the | Its [[Southern Hemisphere]] counterpart, marking the most southerly position at which the Sun can be seen directly overhead, is the [[Tropic of Capricorn]]. These tropics are two of the seven major [[circle of latitude|circles of latitude]] that mark maps of Earth, the others being the [[Arctic Circle|Arctic]] and [[Antarctic Circle|Antarctic]] circles the [[Equator]] and the [[Celestial pole|Poles]] (which are degenerate circles). The positions of these two circles of latitude (relative to the Equator) are dictated by the tilt of Earth's [[rotation around a fixed axis|axis of rotation]] relative to the [[orbital plane (astronomy)|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 south of the Tropic of Cancer.<ref>{{cite web |title=NATO - Topic: Collective defence and Article 5 |url=https://www.nato.int/cps/en/natohq/topics_110496.htm |publisher=North Atlantic Treaty Organization |access-date=4 April 2024}}</ref> | 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 south of the Tropic of Cancer.<ref>{{cite web |title=NATO - Topic: Collective defence and Article 5 |url=https://www.nato.int/cps/en/natohq/topics_110496.htm |publisher=North Atlantic Treaty Organization |access-date=4 April 2024}}</ref> | ||
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==Name== | ==Name== | ||
When this line of latitude was named in the last centuries | When this line of latitude was named in the last centuries BC, the Sun was in the constellation [[Cancer (astrology)|Cancer]] ([[Latin]]: ''[[Crab]]'') at the [[June solstice]] (90° [[Ecliptic coordinate system#Ecliptic longitude|ecliptic longitude]]). Due to the [[axial precession|precession of the equinoxes]], this is no longer the case; today the Sun is in the constellation [[Taurus (constellation)|Taurus]] at the June solstice. The word "tropic" itself comes from the Greek "trope (τροπή)", meaning turn (change of direction or circumstance) or inclination, referring to the fact that the Sun appears to "turn back" at the solstices. | ||
==Drift== | ==Drift== | ||
[[File:Trópico de Cáncer en México - Carretera 83 (Vía Corta) Zaragoza-Victoria, Km 27+800.jpg|[[Mexican Federal Highway 83|Carretera 83]] (Vía Corta) Zaragoza-Victoria, km 27+800. Of the Tropic of Cancer's intersections with Mexican federal highways, this | [[File:Trópico de Cáncer en México - Carretera 83 (Vía Corta) Zaragoza-Victoria, Km 27+800.jpg|[[Mexican Federal Highway 83|Carretera 83]] (Vía Corta) Zaragoza-Victoria, km 27+800. Of the Tropic of Cancer's intersections with Mexican federal highways, this was the only one where it is precisely marked and the drift from 2005 to 2010 could be seen. Nowadays, such signs no longer exist.|thumb]] | ||
The Tropic of Cancer's position is not fixed, but constantly changes because of | The Tropic of Cancer's position is not fixed, but constantly changes because of [[axial precession]] 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 about 22.1 to 24.5 degrees, and {{as of|2000|lc=yes}} 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 {{cvt|15|m}}, per year. The circle's position was at exactly 23°27′N in 1917 and will be at 23°26'N in 2045.<ref>[http://www.homepage.montana.edu/~geol445/hyperglac/time1/milankov.htm Montana State University: Milankovitch Cycles & Glaciation] {{webarchive |url=https://web.archive.org/web/20110806021244/http://www.homepage.montana.edu/~geol445/hyperglac/time1/milankov.htm |date=August 6, 2011 }}</ref> | ||
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#Geodesy|equator]], [[axial tilt]] and [[circle of latitude#Movement of the Tropical and Polar circles|circles of latitude]] for additional details. | 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#Geodesy|equator]], [[axial tilt]] and [[circle of latitude#Movement of the Tropical and Polar circles|circles of latitude]] for additional details. | ||
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The climate at the Tropic of Cancer is generally hot and dry, except for cooler highland regions in China, marine environments such as Hawaii, and easterly coastal areas, where [[Precipitation types#Orographic|orographic rainfall]] can be very heavy, in some places reaching {{convert|4|m|in|-1}} annually. Most regions on the Tropic of Cancer experience two distinct seasons: an extremely hot summer with temperatures often reaching {{convert|45|C|F}} and a warm winter with maxima around {{convert|22|C|F}}. Much land on or near the Tropic of Cancer is part of the [[Sahara Desert]], while to the east, the climate is torrid [[monsoon]]al with a short wet season from June to September, and very little rainfall for the rest of the year. | The climate at the Tropic of Cancer is generally hot and dry, except for cooler highland regions in China, marine environments such as Hawaii, and easterly coastal areas, where [[Precipitation types#Orographic|orographic rainfall]] can be very heavy, in some places reaching {{convert|4|m|in|-1}} annually. Most regions on the Tropic of Cancer experience two distinct seasons: an extremely hot summer with temperatures often reaching {{convert|45|C|F}} and a warm winter with maxima around {{convert|22|C|F}}. Much land on or near the Tropic of Cancer is part of the [[Sahara Desert]], while to the east, the climate is torrid [[monsoon]]al 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]]. It had glaciers descending as low as {{convert|2800|m|ft|-1}} during the [[Last Glacial Maximum]]. At present glaciers still exist around<ref>within {{convert|470|km|mi|-1}}</ref> the Tropic. The nearest currently surviving are the [[ | The highest mountain on or adjacent to the Tropic of Cancer is [[Yu Shan]] in [[Taiwan]]. It had glaciers descending as low as {{convert|2800|m|ft|-1}} during the [[Last Glacial Maximum]]. At present glaciers still exist around<ref>within {{convert|470|km|mi|-1}}</ref> the Tropic. The nearest currently surviving are the [[Mingyong Glacier|Minyong]] and [[Baishui glacier|Baishui]] in the [[Himalayas]] to the north and on [[Pico de Orizaba]] in Mexico to the south. | ||
==Circumnavigation== | ==Circumnavigation== | ||
Latest revision as of 05:08, 18 November 2025
Template:Short description Script error: No such module "about". Template:Coord
The Tropic of Cancer, also known as the Northern Tropic,Script error: No such module "Unsubst". is the Earth's northernmost circle of latitude where the Sun can be seen 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 Template:Circle of latitude north of the Equator.
Its Southern Hemisphere counterpart, marking the most southerly position at which the Sun can be seen directly overhead, is the Tropic of Capricorn. These tropics are two of the seven major circles of latitude that mark maps of Earth, the others being the Arctic and Antarctic circles the Equator and the Poles (which are degenerate circles). 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 south of the Tropic of Cancer.[2]
Name
When this line of latitude was named in the last centuries BC, the Sun was in the constellation Cancer (Latin: Crab) at the June solstice (90° ecliptic longitude). Due to the precession of the equinoxes, this is no longer the case; today the Sun is in the constellation Taurus at the June solstice. The word "tropic" itself comes from the Greek "trope (τροπή)", meaning turn (change of direction or circumstance) or inclination, referring to the fact that the Sun appears to "turn back" at the solstices.
Drift
_Zaragoza-Victoria,_Km_27%2B800.jpg){kind=link}
The Tropic of Cancer's position is not fixed, but constantly changes because of axial precession 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 about 22.1 to 24.5 degrees, and Template:As of 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 Template:Cvt, per year. The circle's position was at exactly 23°27′N in 1917 and will be at 23°26'N in 2045.[3]
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
Template: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.[4]
On the Tropic of Cancer 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 17 countries (including two disputed territories) and 8 water bodies, starting at the prime meridian and heading eastward:
| Coordinates (1' accuracy ≈ 2 km ≈ 1 mi) |
Country, territory or sea | Notes |
|---|---|---|
| Template:Coord | Script error: No such module "flag". | |
| Template:Coord | Script error: No such module "flag". | |
| Template:Coord | Script error: No such module "flag". | The Tropic touches on the northernmost point of Script error: No such module "flag". at Template:Coord |
| Template:Coord | Script error: No such module "flag". | The Tropic passes through Lake Nasser |
| Template:Coord | Red Sea | |
| Template:Coord | Script error: No such module "flag". | AlMedinah, Mecca, ArRiyadh, and The Eastern provinces. |
| Template:Coord | Script error: No such module "flag". | Abu Dhabi emirate only |
| Template:Coord | Script error: No such module "flag". | The tropic crosses Muscat, the country's capital. |
| Template:Coord | Indian Ocean | Arabian Sea |
| Template:Coord | Script error: No such module "flag". | States of Gujarat, Rajasthan, Madhya Pradesh, Chhattisgarh, Jharkhand and West Bengal |
| Template:Coord | Script error: No such module "flag". | Khulna, Dhaka, and Chittagong divisions |
| Template:Coord | Script error: No such module "flag". | State of Tripura |
| Template:Coord | Script error: No such module "flag". | Chittagong Division |
| Template:Coord | Script error: No such module "flag". | State of Mizoram |
| Template:Coord | Script error: No such module "flag". | Chin State, Sagaing Division, Mandalay Division, Shan State |
| Template:Coord | Script error: No such module "flag". | Provinces of Yunnan (passing about 7 km north of the border with Script error: No such module "flag".), Guangxi, and Guangdong |
| Template:Coord | Taiwan Strait | |
| Template:Coord | Script error: No such module "flag". | Hujing Island (Huching Island), Chiayi County, Hualien County |
| Template:Coord | Philippine Sea | |
| Template:Coord | Pacific Ocean | Passing just south of Necker Island, Hawaii, Script error: No such module "flag". |
| Template:Coord | Script error: No such module "flag". | State of Baja California Sur |
| Template:Coord | Gulf of California | |
| Template:Coord | Script error: No such module "flag". | States of Sinaloa, Durango, Zacatecas, San Luis Potosí, Nuevo León, and Tamaulipas |
| Template:Coord | Gulf of Mexico | Passing just north of Cuba |
| Template:Coord | Atlantic Ocean | Passing through the Straits of Florida and the Nicholas Channel Passing just south of the Anguilla Cays (Script error: No such module "flag".) Passing through the Santaren Channel and into the open ocean |
| Template:Coord | Script error: No such module "flag". | Exuma Islands and Long Island |
| Template:Coord | Atlantic Ocean | |
| Template:Coord | Western Sahara | Claimed by Script error: No such module "flag". and the Script error: No such module "flag". |
| Template:Coord | Script error: No such module "flag". | |
| Template:Coord | Script error: No such module "flag". | |
| Template:Coord | Script error: No such module "flag". |
Climate
The climate at the Tropic of Cancer is generally hot and dry, except for cooler highland regions in China, marine environments such as Hawaii, and easterly coastal areas, where orographic rainfall can be very heavy, in some places reaching Template:Convert annually. Most regions on the Tropic of Cancer experience two distinct seasons: an extremely hot summer with temperatures often reaching Template:Convert and a warm winter with maxima around Template:Convert. 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. It had glaciers descending as low as Template:Convert during the Last Glacial Maximum. At present glaciers still exist around[5] the Tropic. The nearest currently surviving are the Minyong and Baishui in the Himalayas to the north and on Pico de Orizaba in Mexico to the south.
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.
The length of the Tropic of Cancer is Template:Cvt:[6]
- where φ is the latitude of the Tropic of Cancer
For an ordinary circumnavigation the rules are somewhat relaxed and the distance is set to a rounded value of at least Template:Convert.
Gallery
-
Road sign south of Dakhla, marking the Tropic of Cancer. The sign was placed by Budapest-Bamako rally participants; thus, the inscription is in English and Hungarian.
-
Sign marking the Tropic of Cancer a few kilometres from Rann of Kutch, Gujarat, India
-
Sign marking the Tropic of Cancer in Madhya Pradesh, India
-
Sign marking the Tropic of Cancer on National Highway 34 in Nadia District, West Bengal, India
See also
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References
External links
Template:Sister project Template:Sister project
- Temporal Epoch Calculations
- Useful constants (see: Obliquity of the ecliptic)
Template:Geographical coordinates
- ↑ Script error: No such module "citation/CS1".
- ↑ Script error: No such module "citation/CS1".
- ↑ Montana State University: Milankovitch Cycles & Glaciation Template:Webarchive
- ↑ Script error: No such module "citation/CS1".
- ↑ within Template:Convert
- ↑ Bakker et al., Radio Positioning at Sea: Geodetic Survey Computations Least Squares Adjustment, 1995 (Template:ISBN)