What is the Tropic of Cancer?

The Tropic of Cancer: more than just a line on the map.

The five significant imaginary lines that run across the surface of the globe are the equator, Antarctic and Arctic circles, the Tropic of Cancer and the Tropic of Capricorn. Although the equator is the longest of the latitude lines, the tropics are located on the position of the sun with regards to the earth’s position at two points of the year. All the five imaginary lines are significant in relation to the Earth and the sun. When the latitude lines were identified over 2000 years ago, the sun was located in the constellation of Capricorn and Cancer during the winter solstice and summer solstice respectively, hence the tropics.

Tropic of Cancer

The Tropic of Cancer lies at latitude 23.50 on the north of the equator and runs through several countries in three continents including Africa, Asia, and Europe. The tropic is among the circles of latitude that are used to mark maps of the globe and its position is dictated by the Earth’s axis tilt in relation to the plane of its orbit. When it was named 2000 years ago, the sun was in the constellation Cancer at June Solstice. However, today the sun is at Taurus during the June solstice. The word “tropic” is a Greek word meaning turn or change direction just as the sun does at the solstice.

Geography And Climate Of The Tropic of Cancer

The position of the Tropic of Cancer is flexible. In fact, the position changes in a complex manner over time. Currently, the position of Tropic of Cancer drifts south at the rate of almost half an arcsecond of latitude per year. The north of the Tropic of Cancer is the Subtropics and the North Temperate Zone. The Tropic of Cancer passes through 16 countries including seven countries in Africa and seven countries in Asia. It also passes through the Red Sea, Indian Ocean, Pacific Ocean, Philippine Sea, Gulf of California, and the Atlantic Ocean. The climate of the Tropic of Cancer is generally hot and dry except the easternmost coastal areas where heavy orographic rainfall can occur. Most of the regions of the tropic experience two distinct seasons, extremely hot summer with temperatures averaging 45 degrees C and warm winter with average temperature 22 degrees C. Much of the land in the region is part Sahara Desert while the eastern part is characterized by a torrid monsoonal climate. The highest mountain on the Tropic of Cancer is Mount Yushan located in Taiwan.

Significance Of The Tropic of Cancer

The Tropic of Cancer divides the Earth into several parts for navigation and marking of the northern boundary of the tropics. It is also significant to the Earth’s radiation and formation of the different seasons. Solar insolation is the quantity of solar radiation coming into the Earth. During June solstice, the amount of solar radiation is greatest at the Tropic of Cancer causing the areas around the north of the tropic in the northern hemisphere to be exposed to more solar energy. The solar insolation in the area keeps it warm and creates summer.


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