The winter solstice in the northern hemisphere, on December 21, marks the beginning of the astronomical winter, and on this day, the “shortest” of the year, there are the fewest hours of light, respectively the most hours of darkness.
The solstices (when the day is the shortest – or the longest, in the case of the summer solstice), as well as the equinoxes (when the day is equal to the night) are the consequence of the Earth’s movement around the Sun and the tilt of the Earth’s axis.
As every year, although the meteorological winter arrives as early as December 1, the beginning of the astronomical winter is marked by a precise moment, that of the winter solstice, notes Noi.md with reference to
At the time of the winter solstice, the Sun is therefore in the southern hemisphere of the celestial sphere, at the maximum angular distance of 23° 27′ south from the equator, making its diurnal movement along the circle parallel to the celestial equator, called the “tropic of Capricorn”. This explains, for the middle latitudes of the Earth, the inequality of days and nights, as well as the succession of seasons.
Therefore, in two moments of each year – which are called the solstices – the Earth is inclined the most towards the Sun. The hemisphere most inclined to the Sun has the longest day, while the hemisphere furthest from the Sun has the longest night. During the Northern Hemisphere’s Summer Solstice – which always falls around June 21 – the Southern Hemisphere passes through the Winter Solstice.
Also, during the Northern Hemisphere’s Winter Solstice – which always falls around December 21-22 – in the Southern Hemisphere it’s the Summer Solstice.
