Winter Solstice or December Solstice

Equinoxes and solstices are a result of two things: Earth’s tilt and its orbit around the Sun.

Solstice, the term comes from the Latin words sol and sistere, meaning “Sun” and “to stand still”.

Initially, the naming arose from observations of how the Sun’s apparent path across the sky changes slightly from one day to the next, which is caused by the same process as the subsolar point's movement described above.

In the months leading up to the December solstice, the position of sunrise and sunset creeps southward. On the day of the solstice, it reaches its southernmost point. After that, the daily path of the Sun across the sky begins to creep northward again.

The winter solstice, also called the hibernal solstice, occurs when either of Earth's poles reaches its maximum tilt away from the Sun. This happens twice yearly, once in each hemisphere (Northern and Southern). For that hemisphere, the winter solstice is the day with the shortest period of daylight and longest night of the year, and when the Sun is at its lowest daily maximum elevation in the sky. Each polar region experiences continuous darkness or twilight around its winter solstice. The opposite event is the summer solstice.

Solstice occur because earth is tilt 23.4 degreees to its axis.

There are two solstices every year: one in December and one in June. The December solstice marks the shortest day north of the equator and the longest day in the south.

The subsolar point moves north and south during the year because the Earth’s axis is tilted at an angle of about 23.4° in relation to the ecliptic, an imaginary plane created by Earth’s path around the Sun. In June, the Northern Hemisphere is tilted toward the Sun, and the subsolar point is north of the equator. As the Earth travels toward the opposite side of its orbit, which it reaches in December, the Southern Hemisphere gradually receives more sunlight, and the subsolar point travels south.

The Solstices

The farthest points from the equator where the Sun can appear directly overhead are referred to as the tropics.

The tropics are lines of latitude that circle the Earth above and below the equator, at about 23.4 degrees north and south. This angle is set by Earth’s axial tilt.

There are two moments each year when one of Earth’s poles is tilted the most toward the Sun, and the Sun lies directly above one of the tropics. These moments are the solstices.

The June solstice takes place sometime between June 20 and 22, when the Sun is directly above the Tropic of Cancer in the Northern Hemisphere. As a rough guide, the Tropic of Cancer passes through Mexico, northern Africa, the Middle East, India, and China.

The December solstice happens sometime between December 20 and 23, when the Sun is directly over the Tropic of Capricorn in the Southern Hemisphere. In brief, the Tropic of Capricorn runs through South America, southern Africa, and Australia.

In the Northern Hemisphere, the June solstice and December solstice can be referred to as the summer solstice and winter solstice. In the Southern Hemisphere, June is winter and December is summer.

On the date of the summer solstice, all locations in that hemisphere experience their longest days and shortest nights. The winter solstice produces the shortest days and longest nights.

Shortest Day in the North

Since the Northern Hemisphere is tilted away from the Sun in December, it receives less sunlight during the course of a day. At the solstice, the North Pole's tilt away from the Sun is greatest, so this event marks the shortest day of the year north of the equator.

This effect is greatest in locations that are farther away from the equator. In tropical areas, the shortest day is just a little shorter than 12 hours; in the temperate zone, it is significantly shorter; and places within the Arctic Circle experience polar night, when the Sun does not rise at all.

Longest Day in the South

Conversely, the day of the December solstice is the longest day of the year in the Southern Hemisphere. Here, too, the effect is greater the farther a location is away from the equator.

Places within the Antarctic Circle experience Midnight Sun, when the Sun does not set at night.

Equinoxes and Solstices on Other Planets

Every planet in the solar system, apart from Mercury, is tilted on its axis of rotation. This means each planet has its own equinoxes and solstices.

Venus and Jupiter have small axial tilts of 2.6* and 3.1 degrees, respectively. Venus orbits the Sun more quickly than Earth—in Earth time, an equinox or solstice happens on Venus every couple of months or so. Jupiter orbits more slowly; an equinox or solstice occurs there about every three Earth years.

Mars, Saturn, and Neptune have tilts similar to Earth’s: the values are 25.2, 26.8, and 28.3 degrees, respectively. At the equinoxes on Saturn, the planet’s famous rings appear edge-on as seen from Earth.

Uranus has an axial tilt of 97.8 degrees. This is close to a right angle, meaning the planet appears to lie on its side. Around the solstices on Uranus, the Sun is almost directly overhead one of the planet’s poles.

Venus spins in the opposite direction to most planets, its tilt can be given as 177.4 degrees. In other words, Venus can be thought of like it is spinning upside down.

This year, the winter solstice in the northern hemisphere falls on 21 December, and today we’ll get a little under eight hours of daylight in London. Communities further north will have even shorter days.

From today on, the days will start getting longer.

Today marks the shortest day and longest night of the year. Many around the northern hemisphere will be attending winter solstice celebrations.

The winter solstice begins the pagan festival of Yule - but the astrological phenomena has been observed by cultures all over the world for thousands of years. Typically, festivals marking the solstice are a celebration of light, marking the symbolic rebirth of the Sun.

The winter solstice is still celebrated across many parts of the world today. Its observance in early Germanic traditions makes up some of our modern festive customs, including Christmas trees and putting wreaths on the front door.

Stonehenge is a popular destination for people observing the day, but events take place in many other countries.