Tropic of Capricorn

Lore & Background

When this line of latitude was named, the Sun was in the zodiacal constellation Capricorn at the northern solstice, the date each year when the Sun reaches its zenith at this latitude. Due to the precession of the equinoxes, the Sun now appears in the zodiacal constellation Sagittarius at that solstice. The Tropic of Capricorn is the southernmost latitude where the Sun can be seen directly overhead, and it is the southern of the two tropics, with the Tropic of Cancer as its Northern Hemisphere counterpart.

Its position is not fixed; Earth’s axial tilt varies over a 41,000-year period from about 22.1 to 24.5 degrees, currently at about 23.4 degrees. This wobble causes the Tropic of Capricorn to drift northward at a rate of nearly half an arcsecond (0.468″) of latitude, or about 15 metres per year. In 1917 it was exactly at 23°27′S, and it will be at 23°26′S in 2045. The distance between the Arctic Circle and the Tropic of Capricorn remains essentially constant.

The Tropic of Capricorn is the dividing line between the Southern Temperate Zone to the south and the Tropics to the north. During the June solstice (Southern Hemisphere winter), there are approximately 10 hours and 41 minutes of daylight; during the December solstice (Southern Hemisphere summer), there are 13 hours and 35 minutes of daylight. The length of the Tropic of Capricorn at 23°26′11.7″S is 36,788 km (22,859 mi).

The Line That Divides Seasons

The Tropic of Capricorn sits at approximately 23.5 degrees south latitude and serves as the southernmost boundary of Earth's tropical belt. Everything poleward of this line, stretching all the way to the Antarctic Circle at roughly 66.5 degrees south, falls within what geographers call the south temperate zone. This zone is defined by wider annual temperature swings and more pronounced seasonal shifts compared to the tropics, where the sun's near-perpendicular angle keeps temperatures relatively constant and the primary seasonal difference tends to be rainfall rather than heat. The Tropic of Capricorn thus acts as a climatic dividing line: on its equatorward side, the sun's angle never drops far enough to produce true cold seasons, while on its poleward side, the sun's lower winter angle introduces frosts, cooler months, and the full cycle of four distinct seasons that characterizes temperate living across the globe.

Reader's Guide

Its position is not fixed, but constantly changes because of a slight wobble in the Earth's longitudinal alignment relative to its orbit around the Sun. Earth's axial tilt varies over a 41,000 year period from about 22.1 to 24.5 degrees and currently resides at about 23.4 degrees.

The Tropic of Capricorn is currently drifting northward at a rate of almost half an arcsecond (0.468″) of latitude, or 15 metres, per year. The distance between the Arctic Circle and the Tropic of Capricorn is essentially constant moving in tandem. There are approximately 10 hours and 41 minutes of daylight during the June solstice and 13 hours and 35 minutes of daylight during the December solstice.

Did You Know?

• The Tropic of Capricorn passes through 10 countries: Argentina, Australia, Botswana, Brazil, Chile, Madagascar, Mozambique, Namibia, Paraguay, and South Africa.
• In Australia, areas around the Tropic have some of the world's most variable rainfall.
• West of the Andes, the cold Humboldt Current creates the Atacama Desert, one of the driest in the world.