What are the Tropics of Cancer and Capricorn? | All About the Tropics
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The Earth's Invisible Lines: All About the Tropic of Cancer and the Tropic of Capricorn
When you look at a globe, you see all sorts of thin, drawn lines crisscrossing the Earth. Besides the equator, two specific lines of latitude stand out: the Tropic of Cancer and the Tropic of Capricorn. Together, they form the ecological and geographical boundaries of the tropics. But what do these lines mean exactly, and where do they come from?
The Tropic of Cancer: The Northern Limit of the Sun
The Tropic of Cancer (also known as the Northern Tropic) is the imaginary circle that runs around the Earth at approximately 23 degrees north latitude. This line marks the northernmost point on Earth where the sun can be directly – or perpendicularly – overhead at noon.
This unique phenomenon occurs exactly once a year, during the northern summer solstice around June 21st. If you stand on the Tropic of Cancer at that moment and look up, the sun will be directly overhead, and you will cast virtually no shadow. Geographically, this line passes through fascinating landscapes and countries, ranging from the vast deserts of North Africa and the Middle East to Mexico, India, and China.
The Tropic of Capricorn: The Southern Counterpart
Where the north has its boundary, the Southern Hemisphere has the Tropic of Capricorn (the Southern Tropic). This lies at exactly the same distance from the equator, but at approximately 23.5 degrees south latitude.
In the Southern Hemisphere, the roles are reversed: this is the southernmost latitude where the sun can be directly overhead. This occurs during the southern summer solstice around December 21st, the time when we in Europe are experiencing the darkest and coldest days of the year. The imaginary line cuts through countries and continents such as Chile, Argentina, Namibia, South Africa, and Australia.
Where Do Those Strange Names Come From?
The names of both tropics originate from astronomy over two thousand years ago. When ancient astronomers defined these lines, the sun was in the constellations of the same name at the time of the solstice: Cancer for the northern solstice and Capricorn for the southern.
Although the constellations have shifted due to a slow wobble of the Earth's axis (precession) and the sun is no longer there during those solstices, the classical names have always stuck.
The Heart of the Tropics
Together, the Tropic of Cancer and the Tropic of Capricorn form the outline of the tropical zone, also known as the coffee belt. (read more about the coffee belt here) Everything located in the area between these two lines receives intense solar radiation throughout the year and experiences no true meteorological winters. These two invisible circles fundamentally shape the Earth's climate, nature, and seasons.
