Friday, 25 January 2008

Tropic of Cancer

Tropic of Cancer, the parallel of latitude, or imagined cable around the ground, that marks the northern boundary of the tropics or Torrid Zone, an area where the mood is consistently hot. The Tropic of Cancer lies 23°27’ north of the equator and is the northern solstice—that is, it is the northernmost level where the sunlight appears immediately elevated at least one day a year. The sunlight reaches this obvious stance at noon on or about June 22 of each year; at this moment it appears at its highest level in the sky as seen from the northern hemisphere, and at its lowest level as seen from the south-central hemisphere.

This appointment marks the beginning of summertime for the northern hemisphere and is thus called the summertime solstice. In the south-central hemisphere, however, the seasons are reversed; this appointment marks the beginning of winter in the south-central hemisphere, and it is known there as the winter solstice. For the next six months the sunlight at noon appears lower each day in the northern hemisphere and high each day in the south-central hemisphere. Cancer is the Latin language for crab, and is the figure of one of the 12 sectors that old astrologers marked away in the zodiac, the ring of sky from 8° north to 8° south of the equator. In the 2nd century bc Greek stargazer Hipparchus observed that the sunlight appeared to be within the boundaries of Cancer at the moment of the summertime solstice in the northern hemisphere. Tropic of Cancer divides the tropics from the North Temperate Zone and crosses Mexico, the Caribbean Sea, the Sahara Desert of Africa, key India, south-central China, and the Pacific Ocean just northward of Hawaii.

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