The winter solstice is arriving on Dec. 21, which has been announced by NASA to be among 2017's longest solar days, with the shortest period of sunlight and longest period of night.
A solar day is completed as the Earth makes a full revolution on its axis relative to the motion of the sun. It normally consists of 24 hours but varies throughout different seasons of the year.
Derived from the Latin term "solstitium," the astronomical phenomenon occurs when the Northern Hemisphere has tilted the farthest away from the sun. Throughout this period, the sun is positioned directly above the Tropic of Capricorn that is located 23.5 degrees south of the equator. By contrast, it sits directly over the Tropic of Cancer during the summer solstice.
Lower Temperatures And Shorter Daylight To Be Anticipated
Although the winter solstice is associated with lower temperatures, Dec. 21 will not be the coldest day of 2017. Most places in the United States should expect two to three weeks before temperatures begin to drop.
On average, the coldest temperatures in Boston will be experienced from Jan. 17 to 26, in Chicago from Jan. 17 to 20, and in Miami from Jan. 2 to 22. Temperatures will start rising toward the end of January, with the Earth receiving more heat from the sun.
This year, the winter solstice is occurring at the same moment in all countries around the world. It will happen in the United States at exactly 11:28 a.m. ET, 10:28 a.m. CT, 9:28 a.m. MT, and 8:28 a.m. PT. In 2016, the season started at 5:44 a.m. ET.
The amount of sunlight on Dec. 21 will vary based on location. Areas that are situated north of the equator are to have shorter periods of daytime and longer periods of nighttime. Basically, the farther above the equator a country is located, the colder will be its temperature over winter solstice.
During the period, northern parts of the United Sates are to experience zero to six hours of sunlight daily, while states that lie south will have nine to 10.5 hours. These estimates are based on a map created by Alaskan climatologist Brian Brettschneider.
Ancient Cultures Celebrate Arrival Of Winter Solstice
In world history, the coming of winter has been celebrated by ancient cultures around the world. Scandinavians burned yule logs for 12 days, Romans held gift-givings, and Incas performed animal or human sacrifices. Practices have changed over time. Nowadays, people welcome the season by holding feasts or family gatherings.