Tropic of Cancer

Tropic of Cancer

Tropic of Cancer, parallel of latitude at 23°30' north of the equator; it is the northern boundary of the tropics. This parallel marks the farthest point north at which the sun can be seen directly overhead at noon; north of the parallel the sun appears less than 90° from the southern horizon at any day of the year. The sun reaches its vertical position over the Tropic of Cancer at about June 22, the summer solstice in the Northern Hemisphere. When the Tropic of Cancer was named, the sun was in the constellation Cancer at the time of the summer solstice.
For the novel by Henry Miller, see Tropic of Cancer (novel).

The Tropic of Cancer, or Northern tropic, is one of five major degree measures or major circles of latitude that mark maps of the Earth. It is the northernmost latitude at which the Sun can appear directly overhead at noon. This event occurs at the June solstice, when the northern hemisphere is tilted towards the sun to its maximum extent.

The Tropic of Cancer currently lies 23° 26′ 22″ north of the Equator. North of this latitude are the subtropics and Northern 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 known as the Tropics.

The invisible line is called tropic of cancer, because when it was named the sun was in the direction of the constellation Cancer (Latin for crab) at the June solstice. However, this is no longer true due to the precession of the equinoxes. According to IAU boundaries, the sun now is in Taurus at the June solstice, and according to sidereal astrology, which divides the zodiac into twelve equal parts, the sun is in Gemini at that time. The word "tropic" itself comes from the Greek tropos, meaning turn, referring to the fact that the sun appears to "turn back" at the solstices.

The position of the Tropic of Cancer is not fixed, but varies in a complex manner over time; see under circles of latitude for information.

Geography

Starting at the Prime Meridian and heading eastwards, the Tropic of Cancer passes through:

Country, territory or sea Notes
The Tropic touches on the northernmost point of
Red Sea
Abu Dhabi emirate only
Indian Ocean Arabian Sea
(Burma)
Taiwan Strait
Taiwan, claimed by
Pacific Ocean
Hawaii — sea area only, misses every island, passing between Nihoa and Necker Island
Baja California peninsula
Gulf of California
Gulf of Mexico
Straits of Florida
Exuma Islands and Long Island
Atlantic Ocean
Western Sahara Claimed by

Circumnavigation

According to the Fédération Aéronautique Internationale's rules, 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 as well as cross all meridians and end on the same airfield where it started. This length is set to be 36787.559 kilometres - a number implying a precision which does not exist, considering the variations of the tropic described above.

For an ordinary circumnavigation the rules are somewhat relaxed and the distance is set to a rounded value of 37000 kilometres.

See also

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