Once a year, on the summer solstice (June 21st this year), the sun is directly overhead at the Tropic of Cancer line of latitude, giving us the longest day of the year in the Northern Hemisphere. On this day, the Earth’s axis is tilted most closely toward the sun.
The Tropic of Cancer runs through Baja Sur south of Todos Santos and south of the small town of Santiago on the East Cape. A few miles south of Santiago, at Km 81.5 on highway Mexico 1, you’ll find a Tropic of Cancer monument with a little tourist plaza that was built in 2013. There are a few sculptures, a small open-air chapel, and some shops that sell artisan crafts from nearby villages.
Also called the Northern Tropic, the Tropic of Cancer’s position is always slightly changing because of a slight wobble in the Earth’s longitudinal alignment relative to the plane in which the Earth orbits around the Sun. This wobble means that the Tropic of Cancer is currently drifting southward at a rate of almost 50 feet per year. The line is currently at about 23.26°N.
At the time of the summer solstice, the sun appears in the constellation Gemini, but much earlier in history, it lay in the constellation Cancer, resulting in the name, the Tropic of Cancer. Because of the gradual change in the axis of the Earth, the sun will eventually reappear in the constellation Cancer—in about 24,000 years.