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The Tropic of Cancer is located near Bhopal, India, where it is marked by a yellow line at 2 degrees north latitude along the Bhopal-Sanchi Road. Image courtesy of Yann Forget/Wikimedia Commons (CC BY-SA 3.0)"It was because to me, cancer symbolizes the disease of civilization, the endpoint of the wrong path, the necessity to change course radically, to start completely over from scratch." This quote by author Henry Miller explains the title of his provocative 1934 novel, "Tropic of Cancer." Set in late 1920s and early 1930s France, the book chronicles Miller's experiences as an aspiring writer. Though the inspiration behind the title is fitting, many readers are surprised to discover that its content has no connection to the other Tropic of Cancer. So, what exactly is the Tropic of Cancer, and why does it matter?
To begin with, latitude is a measurement that tells us how far north or south we are from the equator, the imaginary line that divides the Earth in half. The equator's latitude is 0 degrees, and there are 180 imaginary lines (called parallels) that stretch from east to west around the Earth, running parallel to the equator. A "circle of latitude" refers to the imaginary ring connecting all points along a specific parallel. The latitude of the North Pole? Ninety degrees north. The South Pole? Ninety degrees south.
Latitude Circles: Tropics of Cancer and Capricorn
You might be familiar with the North and South Poles, but you may not know about the other key latitude circles. Though not all of them have official names, there are five major ones to be aware of: the equator, the Tropics of Cancer and Capricorn, and the Arctic and Antarctic Circles. The Tropics of Cancer and Capricorn were defined because they are locations where the sun can be directly overhead. For ancient travelers who navigated by the stars, these lines were vital reference points. This is part of why the Tropic of Cancer holds significance.
This world map highlights the Tropics of Capricorn and Cancer. The other two major latitude lines, the Arctic Circle, encircling the northern latitudes, and the Antarctic Circle, encircling the southern latitudes, are not shown.
Jennifer Thermes/Getty ImagesLocated Within the Earth's Tropical Zone
Situated at approximately 2 degrees north latitude (i.e., 2 degrees north of the equator), the Tropic of Cancer represents the northernmost boundary of the tropics. Covering about 36 percent of Earth's surface, the tropics are home to roughly one-third of the world's population. This region encompasses the equator and parts of North America, South America, Africa, Asia, and Australia.
Summer Solstice: The Sun Directly Above
On the summer solstice (around June 21), the sun is positioned directly overhead the Tropic of Cancer, marking the northernmost point on Earth where the sun is directly above at noon. When the Tropic of Cancer was first named about 2,000 years ago, the sun aligned with the constellation Cancer during the June solstice. The name persists, even though the sun now resides in the constellation Taurus at this time of year.
Due to a greater concentration of land in the Northern Hemisphere, the Tropic of Cancer intersects more cities than the Southern Hemisphere's Tropic of Capricorn. The Tropic of Cancer passes through Hawaii, parts of Central America, northern Africa, the Sahara Desert, and near Kolkata, India.
