Why Are The Tropics Of Cancer And Capricorn So Important?

The Tropic of Cancer and Tropic of Capricorn are latitudes to the north and south of the Equator. Latitude is an invisible line that runs around the outside of the Earth in a ring. Expressed in degrees, latitudes run from east to west and are described by their position north or south of the Equator where the Equator is 0° and the north and south poles are 90°. 

There are 180 different latitudes, and each lies along a given degree. Their degree rings connect points at the same degree around the Earth, on parallel loops.

There are five main latitudes that are given specific names ( aside from their degree locations). These are the Equator, Tropic of Cancer, Tropic of Capricorn, Arctic Circle, and Antarctic Circle.

The Equator runs around the very middle of the Earth, at zero degrees, and cuts the Earth evenly into a 'top' northern half and 'bottom' southern half. These halves are known as hemispheres. The Tropic of Cancer is located at 23.5 degrees north and the Tropic of Capricorn is at 23.5 degrees south. The Arctic and Antarctic Circles are at 66.5 degrees north and 66.5 degrees south, respectively.

Tropic Of Cancer

The Tropic of Cancer marks the northern edge of the area of the world known as the tropics. This region makes up 36% of the Earth and holds roughly one-third of the Earth's population. This tropic also passes through more cities than its southern equivalent, as there is a higher percentage of the landmass in the northern hemisphere. The Tropic of Cancer runs through 16 countries on three different continents and six water bodies. These countries include Mexico, the Bahamas, Western Sahara, Mauritania, Mali, Algeria, Libya, Egypt,, Saudi Arabia, UAE, Oman, India, Myanmar, and China.

The sun is directly above the Tropic of Cancer at the summer solstice, which usually falls on June 21. This means that not only is the sun immediately overhead, but this tropic is the farthest point north on Earth where the sun is exactly overhead at noon. 

The latitude got its name from the constellation of Cancer, the crab. At the time of naming, the sun pointed towards the Cancer constellation during the solstice.

Tropic of Capricorn

The Tropic of Capricorn is the southerly equivalent of the Tropic of Cancer and is the southern boundary of the tropics. It sits at 23.5 degrees south and marks the southernmost point on Earth where the sun can be exactly overhead at noon. While the northern Cancer has this phenomenon occur in June, in the southern hemisphere, this date is December 21, which marks the summer solstice in the southern part of the world. Like with the Tropic of Cancer, this latitude was also named because at the time (some 2,000 years ago) the sun pointed towards the constellation of Capricorn during the solstice. Over time, the position of the sun in relation to the other stars has shifted, and the constellations don't line up quite in the same way, but the names still stand and are connected to the constellations. 

The Tropic of Capricorn passes through much more open water than the Tropic of Cancer, but there are still several countries it runs through. These include Chile, Argentina, Paraguay, Brazil, Namibia, Botswana, South Africa, Mozambique, Madagascar, Australia, French Polynesia, and just barely touching New Caledonia, Fiji, Tonga and the Cook Islands and finally Pitcairn island. 

These latitudinal lines were particularly important in the days of ancient travel. Explorers and travelers on both land and sea could use these sun-related and celestial guides to navigate long cross-nation travel. These demarcation lines were crucial to the safe passage across open oceans or areas that were sparsely populated.