Sun Tower 
The Sun reaches its northernmost point in the sky tomorrow, which is the start of summer in the northern hemisphere. At noon, it’ll stand directly above the Tropic of Cancer, an imaginary ring around Earth at a latitude of 23-and-a-half degrees north. It’s named for the constellation Cancer, because centuries ago, the Sun passed through the constellation at the summer solstice.
Many cultures have built monuments along the Tropic of Cancer. In part, that’s because, with the Sun standing directly overhead at noon, objects on the ground cast no shadows.
The monument building continues today. In 1986, for example, China built a structure at the city of Shantou, which is about 200 miles up the coast from Hong Kong. The structure is known as the Symbolic Tower of the Tropic of Cancer.
It’s basically a big pedestal that supports a globe that’s 16 feet in diameter.
Because the monument is built on the Tropic of Cancer, it’s a popular spot for visitors on the summer solstice. At local noon, when the Sun stands straight overhead, sunlight shines directly through a pipe that passes through the globe, illuminating the granite patio beneath it with a circle of intense light.
Visitors who stand below the hole not only have their heads bathed in sunlight, but they cast no shadow. And if they straddle the metal marker beneath the globe, they’ll have one foot in Earth’s tropics and the other in the temperate zone.
More about the solstice tomorrow.
Script by Robert Tindol and Damond Benningfield