Today at 4:48 UTC ( Coordinated Universal Time ) we marked the winter solstice . ( Those of you in Eastern Standard Time experienced it at 11:48 p.m. on December 21 . ) It ’s the longest dark and short day of the twelvemonth in the Northern Hemisphere . So what is a solstice , and why is it affecting your day ?
The Earth does n’t reel vertically like a top as it revolve the Sun . Instead , imagine a line drawn immediately through the Earth at its celestial pole . cant the Earth along that line at 23.5 degree . That is the Earth ’s axile tilt . The counselling of the Earth ’s axial tilt does n’t interchange as it orbits the Sun ( for our timescale , at least ) , which mean the Sun is directly overhead unlike parts of the Earth at different time of the yr . For half the twelvemonth , the Southern Hemisphere is " closer " to the Sun and its radiation ; for the other half , the Northern Hemisphere is faithful . You might recognize this phenomenon as the reason we have seasons .
The axial tilt also affects the duration of days . believe a map of the Earth , with horizontal occupation separate it latitudinally , and vertical line longwise . Among the best - known latitude are the equator , at 0 degrees ; the Northern Hemisphere ’s Tropic of Cancer , at 23.5 degrees ; and the Southern Hemisphere ’s Tropic of Capricorn , at -23.5 degree . Recognize that numeral ? Now we ’re getting somewhere .
The winter solstice in the Northern Hemisphere come when the Tropic of Capricorn live an overhead Sun , which gain that latitude ’s day 13 hour , 27 proceedings long . Because less of the Northern Hemisphere is in unmediated sunlight , the higher up the Earth you get from the Tropic of Capricorn , the shorter the daylight . The Clarence Day is 12 hour long at the equator ; just over 10.5 hour at the Tropic of Cancer ; and 0 hours at the Arctic Circle , which is in total darkness .
If the want of sun on the short day of the year has you weeping into your whisky , take center : Beginning tomorrow , the Day slow start to lengthen again . It may be the first day of winter , but fountain is on the path . On March 20 , 2016 , the Sun will be directly " over " the equator . This is the youthful equinox . The Sun is again over the equator in September — the autumnal equinox . And exactly halfway between them is the Clarence Shepard Day Jr. that sunlight believer probably consider the best one of the yr : the summer solstice , when the Sun is straight over the Tropic of Cancer .
