Kääntöpiiriä

Kääntöpiiriä refers to the two lines of latitude on Earth that are approximately 23.5 degrees north and south of the Equator. These lines are significant because they mark the most northerly and southerly points at which the Sun can be directly overhead. The northern kääntöpiiriä is known as the Tropic of Cancer, and the southern kääntöpiiriä is known as the Tropic of Capricorn.

The geographical position of these kääntöpiiriä is determined by the tilt of the Earth's axis, which is approximately 23.5 degrees relative to its orbital plane around the Sun. This tilt is the cause of the seasons. When the Northern Hemisphere is tilted towards the Sun, the Sun appears directly overhead at the Tropic of Cancer, marking the summer solstice in the Northern Hemisphere. Conversely, when the Southern Hemisphere is tilted towards the Sun, the Sun appears directly overhead at the Tropic of Capricorn, marking the summer solstice in the Southern Hemisphere and the winter solstice in the Northern Hemisphere.

The region between the Tropic of Cancer and the Tropic of Capricorn is known as the tropics. This zone experiences generally warm temperatures throughout the year and receives a significant amount of solar radiation. Outside of these kääntöpiiriä, in the temperate and polar regions, the Sun's rays strike the Earth at a more oblique angle, resulting in less intense heat and more distinct seasonal variations. The kääntöpiiriä are therefore crucial geographical markers for understanding climate patterns and astronomical phenomena on Earth.